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diff --git a/Build/source/texk/web2c/pktogf.web b/Build/source/texk/web2c/pktogf.web new file mode 100644 index 00000000000..8fc8a0256f6 --- /dev/null +++ b/Build/source/texk/web2c/pktogf.web @@ -0,0 +1,1727 @@ +% PKtoGF.web +% +% PKtoGF creates a generic font file from a packed pixel file. +% +% Preliminary 0.0 version: January, 1988 +% Fixed bug to include specials in character (1.0): January 1988 +% Cleaned up description (bitweight errors) no version change: July 1990 +% Fixed bug with empty character setting min_n to 1 (1.1): 19 October 1990 +\def\versiondate{19 October 1990} +% +\font\ninerm=cmr9 +\let\mc=\ninerm % medium caps for names like PASCAL +\font\logo=logo10 % font used for the METAFONT logo +\def\MF{{\logo META}\-{\logo FONT}} +\def\PASCAL{{\mc Pascal}} +\def\tamu{Texas A\char38 M} +\def\(#1){} % this is used to make section names sort themselves better +\def\9#1{} % this is used for sort keys in the index +\def\title{PKtoGF} +\def\contentspagenumber{0} +\def\topofcontents{\null + \def\titlepage{F} % include headline on the contents page + \def\rheader{\mainfont\hfil \contentspagenumber} + \vfill + \centerline{\titlefont The {\ttitlefont PKtoGF} processor} + \vskip 15pt + \centerline{(Version 1.1, \versiondate)} + \vfill} +\def\botofcontents{\vfill + \centerline{\hsize 5in\baselineskip9pt + \vbox{\ninerm\noindent + The preparation of this report + was supported in part by the National Science + Foundation under grants IST-8201926 and MCS-8300984, + and by the System Development Foundation. `\TeX' is a + trademark of the American Mathematical Society.}}} +\pageno=\contentspagenumber \advance\pageno by 1 + +@* Introduction. +This program takes a packed, or \.{PK} file, and converts it into the +standard \.{GF} format. The resulting \.{GF} file is standard in +every way, and is essentially identical to the \.{GF} file from which +the \.{PK} file was produced in the first place. Note that, however, +\.{GF} to \.{PK} to \.{GF} is not an exact identity transformation, as +the new \.{GF} file will have a different preamble string and the actual +minimum bounding box will be used, instead of a possibly larger bounding +box in the original \.{GF} file. + +@ The |banner| string defined here should be changed whenever \.{PKtoGF} +gets modified. You should update the preamble comment as well. + +@d banner=='This is PKtoGF, Version 1.1' + {printed when the program starts} +@d preamble_comment=='PKtoGF 1.1 output' +@d comm_length==17 + +@ This program is written in standard \PASCAL, except where it is necessary +to use extensions; for example, \.{PKtoGF} must read files whose names +are dynamically specified, and that would be impossible in pure \PASCAL. + +@d othercases == others: {default for cases not listed explicitly} +@d endcases == @+end {follows the default case in an extended |case| statement} +@f othercases == else +@f endcases == end + +@ Both the input and output come from binary files. On line interaction +is handled through \PASCAL's standard |input| and |output| files. + +@d print_ln(#)==write_ln(output,#) +@d print(#)==write(output,#) + +@p program PKtoGF(input, output); +label @<Labels in the outer block@>@/ +const @<Constants in the outer block@>@/ +type @<Types in the outer block@>@/ +var @<Globals in the outer block@>@/ +procedure initialize; {this procedure gets things started properly} + var i:integer; {loop index for initializations} + begin print_ln(banner);@/ + @<Set initial values@>@/ + end; + +@ If the program has to stop prematurely, it goes to the +`|final_end|'. + +@d final_end=9999 {label for the end of it all} + +@<Labels...@>=final_end; + +@ These constants determine the maximum length of a file name and the length +of the terminal line, as well as the maximum number of run counts allowed +per line of the \.{GF} file. (We need this to implement repeat counts.) +@^system dependancies@> + +@<Constants...@>= +@!name_length=80; {maximum length of a file name} +@!terminal_line_length=132; {maximum length of an input line} +@!max_counts=400; {maximum number of run counts in a raster line} + +@ Here are some macros for common programming idioms. + +@d incr(#) == #:=#+1 {increase a variable by unity} +@d decr(#) == #:=#-1 {decrease a variable by unity} +@d do_nothing == {empty statement} + +@ It is possible that a malformed packed file (heaven forbid!) or some other +error might be detected by this program. Such errors might occur in a deeply +nested procedure, so the procedure called |jump_out| has been added to transfer +to the very end of the program with an error message. + +@d abort(#)==begin print_ln(' ',#); jump_out; end + +@p procedure jump_out; +begin goto final_end; +end; + +@* The character set. +Like all programs written with the \.{WEB} system, \.{PKtoGF} can be +used with any character set. But it uses ASCII code internally, because +the programming for portable input-output is easier when a fixed internal +code is used. + +The next few sections of \.{PKtoGF} have therefore been copied from the +analogous ones in the \.{WEB} system routines. They have been considerably +simplified, since \.{PKtoGF} need not deal with the controversial +ASCII codes less than @'40. + +@<Types...@>= +@!ASCII_code=" ".."~"; {a subrange of the integers} + +@ The original \PASCAL\ compiler was designed in the late 60s, when six-bit +character sets were common, so it did not make provision for lower case +letters. Nowadays, of course, we need to deal with both upper and lower case +alphabets in a convenient way, especially in a program like \.{GFtoPK}. +So we shall assume that the \PASCAL\ system being used for \.{GFtoPK} +has a character set containing at least the standard visible characters +of ASCII code (|"!"| through |"~"|). + +Some \PASCAL\ compilers use the original name |char| for the data type +associated with the characters in text files, while other \PASCAL s +consider |char| to be a 64-element subrange of a larger data type that has +some other name. In order to accommodate this difference, we shall use +the name |text_char| to stand for the data type of the characters in the +output file. We shall also assume that |text_char| consists of +the elements |chr(first_text_char)| through |chr(last_text_char)|, +inclusive. The following definitions should be adjusted if necessary. +@^system dependencies@> + +@d text_char == char {the data type of characters in text files} +@d first_text_char=0 {ordinal number of the smallest element of |text_char|} +@d last_text_char=127 {ordinal number of the largest element of |text_char|} + +@<Types...@>= +@!text_file=packed file of text_char; + +@ The \.{GFtoPK} processor converts between ASCII code and +the user's external character set by means of arrays |xord| and |xchr| +that are analogous to \PASCAL's |ord| and |chr| functions. + +@<Globals...@>= +@!xord: array [text_char] of ASCII_code; + {specifies conversion of input characters} +@!xchr: array [0..255] of text_char; + {specifies conversion of output characters} + +@ Under our assumption that the visible characters of standard ASCII are +all present, the following assignment statements initialize the +|xchr| array properly, without needing any system-dependent changes. + +@<Set init...@>= +for i:=0 to @'37 do xchr[i]:='?'; +xchr[@'40]:=' '; +xchr[@'41]:='!'; +xchr[@'42]:='"'; +xchr[@'43]:='#'; +xchr[@'44]:='$'; +xchr[@'45]:='%'; +xchr[@'46]:='&'; +xchr[@'47]:='''';@/ +xchr[@'50]:='('; +xchr[@'51]:=')'; +xchr[@'52]:='*'; +xchr[@'53]:='+'; +xchr[@'54]:=','; +xchr[@'55]:='-'; +xchr[@'56]:='.'; +xchr[@'57]:='/';@/ +xchr[@'60]:='0'; +xchr[@'61]:='1'; +xchr[@'62]:='2'; +xchr[@'63]:='3'; +xchr[@'64]:='4'; +xchr[@'65]:='5'; +xchr[@'66]:='6'; +xchr[@'67]:='7';@/ +xchr[@'70]:='8'; +xchr[@'71]:='9'; +xchr[@'72]:=':'; +xchr[@'73]:=';'; +xchr[@'74]:='<'; +xchr[@'75]:='='; +xchr[@'76]:='>'; +xchr[@'77]:='?';@/ +xchr[@'100]:='@@'; +xchr[@'101]:='A'; +xchr[@'102]:='B'; +xchr[@'103]:='C'; +xchr[@'104]:='D'; +xchr[@'105]:='E'; +xchr[@'106]:='F'; +xchr[@'107]:='G';@/ +xchr[@'110]:='H'; +xchr[@'111]:='I'; +xchr[@'112]:='J'; +xchr[@'113]:='K'; +xchr[@'114]:='L'; +xchr[@'115]:='M'; +xchr[@'116]:='N'; +xchr[@'117]:='O';@/ +xchr[@'120]:='P'; +xchr[@'121]:='Q'; +xchr[@'122]:='R'; +xchr[@'123]:='S'; +xchr[@'124]:='T'; +xchr[@'125]:='U'; +xchr[@'126]:='V'; +xchr[@'127]:='W';@/ +xchr[@'130]:='X'; +xchr[@'131]:='Y'; +xchr[@'132]:='Z'; +xchr[@'133]:='['; +xchr[@'134]:='\'; +xchr[@'135]:=']'; +xchr[@'136]:='^'; +xchr[@'137]:='_';@/ +xchr[@'140]:='`'; +xchr[@'141]:='a'; +xchr[@'142]:='b'; +xchr[@'143]:='c'; +xchr[@'144]:='d'; +xchr[@'145]:='e'; +xchr[@'146]:='f'; +xchr[@'147]:='g';@/ +xchr[@'150]:='h'; +xchr[@'151]:='i'; +xchr[@'152]:='j'; +xchr[@'153]:='k'; +xchr[@'154]:='l'; +xchr[@'155]:='m'; +xchr[@'156]:='n'; +xchr[@'157]:='o';@/ +xchr[@'160]:='p'; +xchr[@'161]:='q'; +xchr[@'162]:='r'; +xchr[@'163]:='s'; +xchr[@'164]:='t'; +xchr[@'165]:='u'; +xchr[@'166]:='v'; +xchr[@'167]:='w';@/ +xchr[@'170]:='x'; +xchr[@'171]:='y'; +xchr[@'172]:='z'; +xchr[@'173]:='{'; +xchr[@'174]:='|'; +xchr[@'175]:='}'; +xchr[@'176]:='~'; +for i:=@'177 to 255 do xchr[i]:='?'; + +@ The following system-independent code makes the |xord| array contain a +suitable inverse to the information in |xchr|. + +@<Set init...@>= +for i:=first_text_char to last_text_char do xord[chr(i)]:=@'40; +for i:=" " to "~" do xord[xchr[i]]:=i; + +@* Generic font file format. +The most important output produced by a typical run of \MF\ is the +``generic font'' (\.{GF}) file that specifies the bit patterns of the +characters that have been drawn. The term {\sl generic\/} indicates that +this file format doesn't match the conventions of any name-brand manufacturer; +but it is easy to convert \.{GF} files to the special format required by +almost all digital phototypesetting equipment. There's a strong analogy +between the \.{DVI} files written by \TeX\ and the \.{GF} files written +by \MF; and, in fact, the file formats have a lot in common. + +A \.{GF} file is a stream of 8-bit bytes that may be +regarded as a series of commands in a machine-like language. The first +byte of each command is the operation code, and this code is followed by +zero or more bytes that provide parameters to the command. The parameters +themselves may consist of several consecutive bytes; for example, the +`|boc|' (beginning of character) command has six parameters, each of +which is four bytes long. Parameters are usually regarded as nonnegative +integers; but four-byte-long parameters can be either positive or +negative, hence they range in value from $-2^{31}$ to $2^{31}-1$. +As in \.{TFM} files, numbers that occupy +more than one byte position appear in BigEndian order, +and negative numbers appear in two's complement notation. + +A \.{GF} file consists of a ``preamble,'' followed by a sequence of one or +more ``characters,'' followed by a ``postamble.'' The preamble is simply a +|pre| command, with its parameters that introduce the file; this must come +first. Each ``character'' consists of a |boc| command, followed by any +number of other commands that specify ``black'' pixels, +followed by an |eoc| command. The characters appear in the order that \MF\ +generated them. If we ignore no-op commands (which are allowed between any +two commands in the file), each |eoc| command is immediately followed by a +|boc| command, or by a |post| command; in the latter case, there are no +more characters in the file, and the remaining bytes form the postamble. +Further details about the postamble will be explained later. + +Some parameters in \.{GF} commands are ``pointers.'' These are four-byte +quantities that give the location number of some other byte in the file; +the first file byte is number~0, then comes number~1, and so on. + +@ The \.{GF} format is intended to be both compact and easily interpreted +by a machine. Compactness is achieved by making most of the information +relative instead of absolute. When a \.{GF}-reading program reads the +commands for a character, it keeps track of two quantities: (a)~the current +column number,~|m|; and (b)~the current row number,~|n|. These are 32-bit +signed integers, although most actual font formats produced from \.{GF} +files will need to curtail this vast range because of practical +limitations. (\MF\ output will never allow $\vert m\vert$ or $\vert +n\vert$ to get extremely large, but the \.{GF} format tries to be more +general.) + +How do \.{GF}'s row and column numbers correspond to the conventions +of \TeX\ and \MF? Well, the ``reference point'' of a character, in \TeX's +view, is considered to be at the lower left corner of the pixel in row~0 +and column~0. This point is the intersection of the baseline with the left +edge of the type; it corresponds to location $(0,0)$ in \MF\ programs. +Thus the pixel in \.{GF} row~0 and column~0 is \MF's unit square, comprising +the region of the plane whose coordinates both lie between 0 and~1. The +pixel in \.{GF} row~|n| and column~|m| consists of the points whose \MF\ +coordinates |(x,y)| satisfy |m<=x<=m+1| and |n<=y<=n+1|. Negative values of +|m| and~|x| correspond to columns of pixels {\sl left\/} of the reference +point; negative values of |n| and~|y| correspond to rows of pixels {\sl +below\/} the baseline. + +Besides |m| and |n|, there's also a third aspect of the current +state, namely the @!|paint_switch|, which is always either \\{black} or +\\{white}. Each \\{paint} command advances |m| by a specified amount~|d|, +and blackens the intervening pixels if |paint_switch=black|; then +the |paint_switch| changes to the opposite state. \.{GF}'s commands are +designed so that |m| will never decrease within a row, and |n| will never +increase within a character; hence there is no way to whiten a pixel that +has been blackened. + +@ Here is a list of all the commands that may appear in a \.{GF} file. Each +command is specified by its symbolic name (e.g., |boc|), its opcode byte +(e.g., 67), and its parameters (if any). The parameters are followed +by a bracketed number telling how many bytes they occupy; for example, +`|d[2]|' means that parameter |d| is two bytes long. + +\yskip\hang|paint_0| 0. This is a \\{paint} command with |d=0|; it does +nothing but change the |paint_switch| from \\{black} to \\{white} or +vice~versa. + +\yskip\hang\\{paint\_1} through \\{paint\_63} (opcodes 1 to 63). +These are \\{paint} commands with |d=1| to~63, defined as follows: If +|paint_switch=black|, blacken |d|~pixels of the current row~|n|, +in columns |m| through |m+d-1| inclusive. Then, in any case, +complement the |paint_switch| and advance |m| by~|d|. + +\yskip\hang|paint1| 64 |d[1]|. This is a \\{paint} command with a specified +value of~|d|; \MF\ uses it to paint when |64<=d<256|. + +\yskip\hang|@!paint2| 65 |d[2]|. Same as |paint1|, but |d|~can be as high +as~65535. + +\yskip\hang|@!paint3| 66 |d[3]|. Same as |paint1|, but |d|~can be as high +as $2^{24}-1$. \MF\ never needs this command, and it is hard to imagine +anybody making practical use of it; surely a more compact encoding will be +desirable when characters can be this large. But the command is there, +anyway, just in case. + +\yskip\hang|boc| 67 |c[4]| |p[4]| |min_m[4]| |max_m[4]| |min_n[4]| +|max_n[4]|. Beginning of a character: Here |c| is the character code, and +|p| points to the previous character beginning (if any) for characters having +this code number modulo 256. (The pointer |p| is |-1| if there was no +prior character with an equivalent code.) The values of registers |m| and |n| +defined by the instructions that follow for this character must +satisfy |min_m<=m<=max_m| and |min_n<=n<=max_n|. (The values of |max_m| and +|min_n| need not be the tightest bounds possible.) When a \.{GF}-reading +program sees a |boc|, it can use |min_m|, |max_m|, |min_n|, and |max_n| to +initialize the bounds of an array. Then it sets |m:=min_m|, |n:=max_n|, and +|paint_switch:=white|. + +\yskip\hang|boc1| 68 |c[1]| |@!del_m[1]| |max_m[1]| |@!del_n[1]| |max_n[1]|. +Same as |boc|, but |p| is assumed to be~$-1$; also |del_m=max_m-min_m| +and |del_n=max_n-min_n| are given instead of |min_m| and |min_n|. +The one-byte parameters must be between 0 and 255, inclusive. +\ (This abbreviated |boc| saves 19~bytes per character, in common cases.) + +\yskip\hang|eoc| 69. End of character: All pixels blackened so far +constitute the pattern for this character. In particular, a completely +blank character might have |eoc| immediately following |boc|. + +\yskip\hang|skip0| 70. Decrease |n| by 1 and set |m:=min_m|, +|paint_switch:=white|. \ (This finishes one row and begins another, +ready to whiten the leftmost pixel in the new row.) + +\yskip\hang|skip1| 71 |d[1]|. Decrease |n| by |d+1|, set |m:=min_m|, and set +|paint_switch:=white|. This is a way to produce |d| all-white rows. + +\yskip\hang|@!skip2| 72 |d[2]|. Same as |skip1|, but |d| can be as large +as 65535. + +\yskip\hang|@!skip3| 73 |d[3]|. Same as |skip1|, but |d| can be as large +as $2^{24}-1$. \MF\ obviously never needs this command. + +\yskip\hang|new_row_0| 74. Decrease |n| by 1 and set |m:=min_m|, +|paint_switch:=black|. \ (This finishes one row and begins another, +ready to {\sl blacken\/} the leftmost pixel in the new row.) + +\yskip\hang|@!new_row_1| through |@!new_row_164| (opcodes 75 to 238). Same as +|new_row_0|, but with |m:=min_m+1| through |min_m+164|, respectively. + +\yskip\hang|xxx1| 239 |k[1]| |x[k]|. This command is undefined in +general; it functions as a $(k+2)$-byte |no_op| unless special \.{GF}-reading +programs are being used. \MF\ generates \\{xxx} commands when encountering +a \&{special} string; this occurs in the \.{GF} file only between +characters, after the preamble, and before the postamble. However, +\\{xxx} commands might appear anywhere in \.{GF} files generated by other +processors. It is recommended that |x| be a string having the form of a +keyword followed by possible parameters relevant to that keyword. + +\yskip\hang|@!xxx2| 240 |k[2]| |x[k]|. Like |xxx1|, but |0<=k<65536|. + +\yskip\hang|xxx3| 241 |k[3]| |x[k]|. Like |xxx1|, but |0<=k<@t$2^{24}$@>|. +\MF\ uses this when sending a \&{special} string whose length exceeds~255. + +\yskip\hang|@!xxx4| 242 |k[4]| |x[k]|. Like |xxx1|, but |k| can be +ridiculously large; |k| mustn't be negative. + +\yskip\hang|yyy| 243 |y[4]|. This command is undefined in general; +it functions as a 5-byte |no_op| unless special \.{GF}-reading programs +are being used. \MF\ puts |scaled| numbers into |yyy|'s, as a +result of \&{numspecial} commands; the intent is to provide numeric +parameters to \\{xxx} commands that immediately precede. + +\yskip\hang|no_op| 244. No operation, do nothing. Any number of |no_op|'s +may occur between \.{GF} commands, but a |no_op| cannot be inserted between +a command and its parameters or between two parameters. + +\yskip\hang|char_loc| 245 |c[1]| |dx[4]| |dy[4]| |w[4]| |p[4]|. +This command will appear only in the postamble, which will be explained +shortly. + +\yskip\hang|@!char_loc0| 246 |c[1]| |@!dm[1]| |w[4]| |p[4]|. +Same as |char_loc|, except that |dy| is assumed to be zero, and the value +of~|dx| is taken to be |65536*dm|, where |0<=dm<256|. + +\yskip\hang|pre| 247 |i[1]| |k[1]| |x[k]|. +Beginning of the preamble; this must come at the very beginning of the +file. Parameter |i| is an identifying number for \.{GF} format, currently +131. The other information is merely commentary; it is not given +special interpretation like \\{xxx} commands are. (Note that \\{xxx} +commands may immediately follow the preamble, before the first |boc|.) + +\yskip\hang|post| 248. Beginning of the postamble, see below. + +\yskip\hang|post_post| 249. Ending of the postamble, see below. + +\yskip\noindent Commands 250--255 are undefined at the present time. + +@d gf_id_byte=131 {identifies the kind of \.{GF} files described here} + +@ Here are the opcodes that \.{GFtoPK} actually refers to. + +@d paint_0=0 {beginning of the \\{paint} commands} +@d paint1=64 {move right a given number of columns, then + black${}\leftrightarrow{}$white} +@d boc=67 {beginning of a character} +@d boc1=68 {abbreviated |boc|} +@d eoc=69 {end of a character} +@d skip0=70 {skip no blank rows} +@d skip1=71 {skip over blank rows} +@d new_row_0=74 {move down one row and then right} +@d max_new_row=238 {move down one row and then right} +@d no_op=247 {noop} +@d xxx1=239 {for \&{special} strings} +@d yyy=243 {for \&{numspecial} numbers} +@d nop=244 {no operation} +@d char_loc=245 {character locators in the postamble} +@d char_loc0=246 {character locators in the postamble} +@d pre=247 {preamble} +@d post=248 {postamble beginning} +@d post_post=249 {postamble ending} +@d undefined_commands==250,251,252,253,254,255 + +@ The last character in a \.{GF} file is followed by `|post|'; this command +introduces the postamble, which summarizes important facts that \MF\ has +accumulated. The postamble has the form +$$\vbox{\halign{\hbox{#\hfil}\cr + |post| |p[4]| |@!ds[4]| |@!cs[4]| |@!hppp[4]| |@!vppp[4]| + |@!min_m[4]| |@!max_m[4]| |@!min_n[4]| |@!max_n[4]|\cr + $\langle\,$character locators$\,\rangle$\cr + |post_post| |q[4]| |i[1]| 223's$[{\G}4]$\cr}}$$ +Here |p| is a pointer to the byte following the final |eoc| in the file +(or to the byte following the preamble, if there are no characters); +it can be used to locate the beginning of \\{xxx} commands +that might have preceded the postamble. The |ds| and |cs| parameters +@^design size@> @^check sum@> +give the design size and check sum, respectively, which are exactly the +values put into the header of any \.{TFM} file that shares information with +this \.{GF} file. Parameters |hppp| and |vppp| are the ratios of +pixels per point, horizontally and vertically, expressed as |scaled| integers +(i.e., multiplied by $2^{16}$); they can be used to correlate the font +with specific device resolutions, magnifications, and ``at sizes.'' Then +come |min_m|, |max_m|, |min_n|, and |max_n|, which bound the values that +registers |m| and~|n| assume in all characters in this \.{GF} file. +(These bounds need not be the best possible; |max_m| and |min_n| may, on the +other hand, be tighter than the similar bounds in |boc| commands. For +example, some character may have |min_n=-100| in its |boc|, but it might +turn out that |n| never gets lower than |-50| in any character; then +|min_n| can have any value |<=-50|. If there are no characters in the file, +it's possible to have |min_m>max_m| and/or |min_n>max_n|.) + +@ Character locators are introduced by |char_loc| commands, +which specify a character residue~|c|, character escapements (|dx,dy|), +a character width~|w|, and a pointer~|p| +to the beginning of that character. (If two or more characters have the +same code~|c| modulo 256, only the last will be indicated; the others can be +located by following backpointers. Characters whose codes differ by a +multiple of 256 are assumed to share the same font metric information, +hence the \.{TFM} file contains only residues of character codes modulo~256. +This convention is intended for oriental languages, when there are many +character shapes but few distinct widths.) +@^oriental characters@>@^Chinese characters@>@^Japanese characters@> + +The character escapements (|dx,dy|) are the values of \MF's \&{chardx} +and \&{chardy} parameters; they are in units of |scaled| pixels; +i.e., |dx| is in horizontal pixel units times $2^{16}$, and |dy| is in +vertical pixel units times $2^{16}$. This is the intended amount of +displacement after typesetting the character; for \.{DVI} files, |dy| +should be zero, but other document file formats allow nonzero vertical +escapement. + +The character width~|w| duplicates the information in the \.{TFM} file; it +is $2^{24}$ times the ratio of the true width to the font's design size. + +The backpointer |p| points to the character's |boc|, or to the first of +a sequence of consecutive \\{xxx} or |yyy| or |no_op| commands that +immediately precede the |boc|, if such commands exist; such ``special'' +commands essentially belong to the characters, while the special commands +after the final character belong to the postamble (i.e., to the font +as a whole). This convention about |p| applies also to the backpointers +in |boc| commands, even though it wasn't explained in the description +of~|boc|. @^backpointers@> + +Pointer |p| might be |-1| if the character exists in the \.{TFM} file +but not in the \.{GF} file. This unusual situation can arise in \MF\ output +if the user had |proofing<0| when the character was being shipped out, +but then made |proofing>=0| in order to get a \.{GF} file. + +@ The last part of the postamble, following the |post_post| byte that +signifies the end of the character locators, contains |q|, a pointer to the +|post| command that started the postamble. An identification byte, |i|, +comes next; this currently equals~131, as in the preamble. + +The |i| byte is followed by four or more bytes that are all equal to +the decimal number 223 (i.e., @'337 in octal). \MF\ puts out four to seven of +these trailing bytes, until the total length of the file is a multiple of +four bytes, since this works out best on machines that pack four bytes per +word; but any number of 223's is allowed, as long as there are at least four +of them. In effect, 223 is a sort of signature that is added at the very end. +@^Fuchs, David Raymond@> + +This curious way to finish off a \.{GF} file makes it feasible for +\.{GF}-reading programs to find the postamble first, on most computers, +even though \MF\ wants to write the postamble last. Most operating +systems permit random access to individual words or bytes of a file, so +the \.{GF} reader can start at the end and skip backwards over the 223's +until finding the identification byte. Then it can back up four bytes, read +|q|, and move to byte |q| of the file. This byte should, of course, +contain the value 248 (|post|); now the postamble can be read, so the +\.{GF} reader can discover all the information needed for individual +characters. + +Unfortunately, however, standard \PASCAL\ does not include the ability to +@^system dependencies@> +access a random position in a file, or even to determine the length of a file. +Almost all systems nowadays provide the necessary capabilities, so \.{GF} +format has been designed to work most efficiently with modern operating +systems. \.{GFtoPK} first reads the postamble, and then scans the file from +front to back. + +@* Packed file format. +The packed file format is a compact representation of the data contained in a +\.{GF} file. The information content is the same, but packed (\.{PK}) files +are almost always less than half the size of their \.{GF} counterparts. They +are also easier to convert into a raster representation because they do not +have a profusion of \\{paint}, \\{skip}, and \\{new\_row} commands to be +separately interpreted. In addition, the \.{PK} format expressedly forbids +\&{special} commands within a character. The minimum bounding box for each +character is explicit in the format, and does not need to be scanned for as in +the \.{GF} format. Finally, the width and escapement values are combined with +the raster information into character ``packets'', making it simpler in many +cases to process a character. + +A \.{PK} file is organized as a stream of 8-bit bytes. At times, these bytes +might be split into 4-bit nybbles or single bits, or combined into multiple +byte parameters. When bytes are split into smaller pieces, the `first' piece +is always the most significant of the byte. For instance, the first bit of +a byte is the bit with value 128; the first nybble can be found by dividing +a byte by 16. Similarly, when bytes are combined into multiple byte +parameters, the first byte is the most significant of the parameter. If the +parameter is signed, it is represented by two's-complement notation. + +The set of possible eight-bit values are separated into two sets, those that +introduce a character definition, and those that do not. The values that +introduce a character definition comprise the range from 0 to 239; byte values +above 239 are interpreted commands. Bytes which introduce character +definitions are called flag bytes, and various fields within the byte indicate +various things about how the character definition is encoded. Command bytes +have zero or more parameters, and can never appear within a character +definition or between parameters of another command, where they would be +interpeted as data. + +A \.{PK} file consists of a preamble, followed by a sequence of one or more +character definitions, followed by a postamble. The preamble command must +be the first byte in the file, followed immediately by its parameters. +Any number of character definitions may follow, and any command but the +preamble command and the postamble command may occur between character +definitions. The very last command in the file must be the postamble. + +@ The packed file format is intended to be easy to read and interpret by +device drivers. The small size of the file reduces the input/output overhead +each time a font is defined. For those drivers that load and save each font +file into memory, the small size also helps reduce the memory requirements. +The length of each character packet is specified, allowing the character raster +data to be loaded into memory by simply counting bytes, rather than +interpreting each command; then, each character can be interpreted on a demand +basis. This also makes it possible for a driver to skip a particular +character quickly if it knows that the character is unused. + +@ First, the command bytes shall be presented; then the format of the +character definitions will be defined. Eight of the possible sixteen +commands (values 240 through 255) are currently defined; the others are +reserved for future extensions. The commands are listed below. Each command +is specified by its symbolic name (e.g., \\{pk\_no\_op}), its opcode byte, +and any parameters. The parameters are followed by a bracketed number +telling how many bytes they occupy, with the number preceded by a plus sign if +it is a signed quantity. (Four byte quantities are always signed, however.) + +\yskip\hang|pk_xxx1| 240 |k[1]| |x[k]|. This command is undefined in general; +it functions as a $(k+2)$-byte \\{no\_op} unless special \.{PK}-reading +programs are being used. \MF\ generates \\{xxx} commands when encountering +a \&{special} string. It is recommended that |x| be a string having the form +of a keyword followed by possible parameters relevant to that keyword. + +\yskip\hang\\{pk\_xxx2} 241 |k[2]| |x[k]|. Like |pk_xxx1|, but |0<=k<65536|. + +\yskip\hang\\{pk\_xxx3} 242 |k[3]| |x[k]|. Like |pk_xxx1|, but +|0<=k<@t$2^{24}$@>|. \MF\ uses this when sending a \&{special} string whose +length exceeds~255. + +\yskip\hang\\{pk\_xxx4} 243 |k[4]| |x[k]|. Like |pk_xxx1|, but |k| can be +ridiculously large; |k| musn't be negative. + +\yskip\hang|pk_yyy| 244 |y[4]|. This command is undefined in general; it +functions as a five-byte \\{no\_op} unless special \.{PK} reading programs +are being used. \MF\ puts |scaled| numbers into |yyy|'s, as a result of +\&{numspecial} commands; the intent is to provide numeric parameters to +\\{xxx} commands that immediately precede. + +\yskip\hang|pk_post| 245. Beginning of the postamble. This command is +followed by enough |pk_no_op| commands to make the file a multiple +of four bytes long. Zero through three bytes are usual, but any number +is allowed. +This should make the file easy to read on machines which pack four bytes to +a word. + +\yskip\hang|pk_no_op| 246. No operation, do nothing. Any number of +|pk_no_op|'s may appear between \.{PK} commands, but a |pk_no_op| cannot be +inserted between a command and its parameters, between two parameters, or +inside a character definition. + +\yskip\hang|pk_pre| 247 |i[1]| |k[1]| |x[k]| |ds[4]| |cs[4]| |hppp[4]| +|vppp[4]|. Preamble command. Here, |i| is the identification byte of the +file, currently equal to 89. The string |x| is merely a comment, usually +indicating the source of the \.{PK} file. The parameters |ds| and |cs| are +the design size of the file in $1/2^{20}$ points, and the checksum of the +file, respectively. The checksum should match the \.{TFM} file and the +\.{GF} files for this font. Parameters |hppp| and |vppp| are the ratios +of pixels per point, horizontally and vertically, multiplied by $2^{16}$; they +can be used to correlate the font with specific device resolutions, +magnifications, and ``at sizes''. Usually, the name of the \.{PK} file is +formed by concatenating the font name (e.g., cmr10) with the resolution at +which the font is prepared in pixels per inch multiplied by the magnification +factor, and the letters \.{PK}. For instance, cmr10 at 300 dots per inch +should be named CMR10.300PK; at one thousand dots per inch and magstephalf, +it should be named CMR10.1095PK. + +@ We put a few of the above opcodes into definitions for symbolic use by +this program. + +@d pk_id = 89 {the version of \.{PK} file described} +@d pk_xxx1 = 240 {\&{special} commands} +@d pk_yyy = 244 {\&{numspecial} commands} +@d pk_post = 245 {postamble} +@d pk_no_op = 246 {no operation} +@d pk_pre = 247 {preamble} + +@ The \.{PK} format has two conflicting goals; to pack character raster and +size information as compactly as possible, while retaining ease of translation +into raster and other forms. A suitable compromise was found in the use of +run-encoding of the raster information. Instead of packing the individual +bits of the character, we instead count the number of consecutive `black' or +`white' pixels in a horizontal raster row, and then encode this number. Run +counts are found for each row, from the top of the character to the bottom. +This is essentially the way the \.{GF} format works. +Instead of presenting each row individually, however, let us concatenate all +of the horizontal raster rows into one long string of pixels, and encode this +row. With knowledge of the width of the bit-map, the original character glyph +can be easily reconstructed. In addition, we do not need special commands to +mark the end of one row and the beginning of the next. + +Next, let us put the burden of finding the minimum bounding box on the part +of the font generator, since the characters will usually be used much more +often than they are generated. The minimum bounding box is the smallest +rectangle which encloses all `black' pixels of a character. Let us also +eliminate the need for a special end of character marker, by supplying +exactly as many bits as are required to fill the minimum bounding box, from +which the end of the character is implicit. + +Let us next consider the distribution of the run counts. Analysis of several +dozen pixel files at 300 dots per inch yields a distribution peaking at four, +falling off slowly until ten, then a bit more steeply until twenty, and then +asymptotically approaching the horizontal. Thus, the great majority of our +run counts will fit in a four-bit nybble. The eight-bit byte is attractive for +our run-counts, as it is the standard on many systems; however, the wasted four +bits in the majority of cases seems a high price to pay. Another possibility +is to use a Huffman-type encoding scheme with a variable number of bits for +each run-count; this was rejected because of the overhead in fetching and +examining individual bits in the file. Thus, the character raster definitions +in the \.{PK} file format are based on the four-bit nybble. + +@ The analysis of the pixel files yielded another interesting statistic: fully +37\char`\%\ +of the raster rows were duplicates of the previous row. Thus, the \.{PK} +format allows the specification of repeat counts, which indicate how many times +a horizontal raster row is to be repeated. These repeated rows are taken out +of the character glyph before individual rows are concatenated into the long +string of pixels. + +For elegance, we disallow a run count of zero. The case of a null raster +description should be gleaned from the character width and height being equal +to zero, and no raster data should be read. No other zero counts are ever +necessary. Also, in the absence of repeat counts, the repeat value is set to +be zero (only the original row is sent.) If a repeat count is seen, it takes +effect on the current row. The current row is defined as the row on which the +first pixel of the next run count will lie. The repeat count is set back to +zero when the last pixel in the current row is seen, and the row is sent out. + +This poses a problem for entirely black and entirely white rows, however. Let +us say that the current row ends with four white pixels, and then we have five +entirely empty rows, followed by a black pixel at the beginning of the next +row, and the character width is ten pixels. We would like to use a repeat +count, but there is no legal place to put it. If we put it before the white +run count, it will apply to the current row. If we put it after, it applies +to the row with the black pixel at the beginning. Thus, entirely white or +entirely black repeated rows are always packed as large run counts (in this +case, a white run count of 54) rather than repeat counts. + +@ Now let us turn our attention to the actual packing of the run counts and +repeat counts into nybbles. There are only sixteen possible nybble values. +We need to indicate run counts and repeat counts. Since the run counts are +much more common, we will devote the majority of the nybble values to them. +We therefore indicate a repeat count by a nybble of 14 followed by a packed +number, where a packed number will be explained later. Since the repeat +count value of one is so common, we indicate a repeat one command by a single +nybble of 15. A 14 followed by the packed number 1 is still legal for a +repeat one count, however. The run counts are coded directly as packed +numbers. + +For packed numbers, therefore, we have the nybble values 0 through 13. We +need to represent the positive integers up to, say, $2^{31}-1$. We would +like the more common smaller numbers to take only one or two nybbles, and +the infrequent large numbers to take three or more. We could therefore +allocate one nybble value to indicate a large run count taking three or more +nybbles. We do this with the value 0. + +@ We are left with the values 1 through 13. We can allocate some of these, say +|dyn_f|, to be one-nybble run counts. +These will work for the run counts |1..dyn_f|. For subsequent run +counts, we will use a nybble greater than |dyn_f|, followed by a second nybble, +whose value can run from 0 through 15. Thus, the two-byte nybble values will +run from |dyn_f+1..(13-dyn_f)*16+dyn_f|. We have our definition of large run +count values now, being all counts greater than |(13-dyn_f)*16+dyn_f|. + +We can analyze our several dozen pixel files and determine an optimal value of +|dyn_f|, and use this value for all of the characters. Unfortunately, values +of |dyn_f| that pack small characters well tend to pack the large characters +poorly, and values that pack large characters well are not efficient for the +smaller characters. Thus, we choose the optimal |dyn_f| on a character basis, +picking the value which will pack each individual character in the smallest +number of nybbles. Legal values of |dyn_f| run from 0 (with no one-byte run +counts) to 13 (with no two-byte run counts). + +@ Our only remaining task in the coding of packed numbers is the large run +counts. We use a scheme suggested by D.~E.~Knuth +@^Knuth, D.~E.@> +which will simply and elegantly represent arbitrarily large values. The +general scheme to represent an integer |i| is to write its hexadecimal +representation, with leading zeros removed. Then we count the number of +digits, and prepend one less than that many zeros before the hexadecimal +representation. Thus, the values from one to fifteen occupy one nybble; +the values sixteen through 255 occupy three, the values 256 through 4095 +require five, etc. + +For our purposes, however, we have already represented the numbers one +through |(13-dyn_f)*16+dyn_f|. In addition, the one-nybble values have +already been taken by our other commands, which means that only the values +from sixteen up are available to us for long run counts. Thus, we simply +normalize our long run counts, by subtracting |(13-dyn_f)*16+dyn_f+1| and +adding 16, and then representing the result according to the scheme above. + +@ The final algorithm for decoding the run counts based on the above scheme +might look like this, assuming a procedure called \\{pk\_nyb} is available +to get the next nybble from the file, and assuming that the global +|repeat_count| indicates whether a row needs to be repeated. Note that this +routine is recursive, but since a repeat count can never directly follow +another repeat count, it can only be recursive to one level. + +@<Packed number procedure@>= +function pk_packed_num : integer ; +var i, j, k : integer ; +begin + i := get_nyb ; + if i = 0 then begin + repeat j := get_nyb ; incr(i) ; until j <> 0 ; + while i > 0 do begin j := j * 16 + get_nyb ; decr(i) ; end ; + pk_packed_num := j - 15 + (13-dyn_f)*16 + dyn_f ; + end else if i <= dyn_f then + pk_packed_num := i + else if i < 14 then + pk_packed_num := (i-dyn_f-1)*16+get_nyb+dyn_f+1 + else begin + if i = 14 then + repeat_count := pk_packed_num + else + repeat_count := 1 ; + pk_packed_num := pk_packed_num ; + end ; +end ; + +@ For low resolution fonts, or characters with `gray' areas, run encoding can +often make the character many times larger. Therefore, for those characters +that cannot be encoded efficiently with run counts, the \.{PK} format allows +bit-mapping of the characters. This is indicated by a |dyn_f| value of +14. The bits are packed tightly, by concatenating all of the horizontal raster +rows into one long string, and then packing this string eight bits to a byte. +The number of bytes required can be calculated by |(width*height+7) div 8|. +This format should only be used when packing the character by run counts takes +more bytes than this, although, of course, it is legal for any character. +Any extra bits in the last byte should be set to zero. + +@ At this point, we are ready to introduce the format for a character +descripter. It consists of three parts: a flag byte, a character preamble, +and the raster data. The most significant four bits of the flag byte +yield the |dyn_f| value for that character. (Notice that only values of +0 through 14 are legal for |dyn_f|, with 14 indicating a bit mapped character; +thus, the flag bytes do not conflict with the command bytes, whose upper nybble +is always 15.) The next bit (with weight 8) indicates whether the first run +count is a black count or a white count, with a one indicating a black count. +For bit-mapped characters, this bit should be set to a zero. The next bit +(with weight 4) indicates whether certain later parameters (referred to as size +parameters) are given in one-byte or two-byte quantities, with a one indicating +that they are in two-byte quantities. The last two bits are concatenated on to +the beginning of the length parameter in the character preamble, which will be +explained below. + +However, if the last three bits of the flag byte are all set (normally +indicating that the size parameters are two-byte values and that a 3 should be +prepended to the length parameter), then a long format of the character +preamble should be used instead of one of the short forms. + +Therefore, there are three formats for the character preamble, and which one +is used depends on the least significant three bits of the flag byte. If the +least significant three bits are in the range zero through three, the short +format is used. If they are in the range four through six, the extended short +format is used. Otherwise, if the least significant bits are all set, then +the long form of the character preamble is used. The preamble formats are +explained below. + +\yskip\hang Short form: |flag[1]| |pl[1]| |cc[1]| |tfm[3]| |dm[1]| |w[1]| +|h[1]| |hoff[+1]| |voff[+1]|. +If this format of the character preamble is used, the above +parameters must all fit in the indicated number of bytes, signed or unsigned +as indicated. Almost all of the standard \TeX\ font characters fit; the few +exceptions are fonts such as \.{aminch}. + +\yskip\hang Extended short form: |flag[1]| |pl[2]| |cc[1]| |tfm[3]| |dm[2]| +|w[2]| |h[2]| |hoff[+2]| |voff[+2]|. Larger characters use this extended +format. + +\yskip\hang Long form: |flag[1]| |pl[4]| |cc[4]| |tfm[4]| |dx[4]| |dy[4]| +|w[4]| |h[4]| |hoff[4]| |voff[4]|. This is the general format which +allows all of the +parameters of the \.{GF} file format, including vertical escapement. +\vskip\baselineskip +The |flag| parameter is the flag byte. The parameter |pl| (packet length) +contains the offset +of the byte following this character descripter, with respect to the beginning +of the |tfm| width parameter. This is given so a \.{PK} reading program can, +once it has read the flag byte, packet length, and character code (|cc|), skip +over the character by simply reading this many more bytes. For the two short +forms of the character preamble, the last two bits of the flag byte should be +considered the two most-significant bits of the packet length. For the short +format, the true packet length might be calculated as |(flag mod 4)*256+pl|; +for the extended format, it might be calculated as |(flag mod 4)*65536+pl|. + +The |w| parameter is the width and the |h| parameter is the height in pixels +of the minimum bounding box. The |dx| and |dy| parameters are the horizontal +and vertical escapements, respectively. In the short formats, |dy| is assumed +to be zero and |dm| is |dy| but in pixels; +in the long format, |dx| and |dy| are both +in pixels multiplied by $2^{16}$. The |hoff| is the horizontal offset from the +upper left pixel to the reference pixel; the |voff| is the vertical offset. +They are both given in pixels, with right and down being positive. The +reference pixel is the pixel which occupies the unit square in \MF; the +\MF\ reference point is the lower left hand corner of this pixel. (See the +example below.) + +@ \TeX\ requires that all characters which have the same character codes +modulo 256 also have the same |tfm| widths, and escapement values. The \.{PK} +format does not itself make this a requirement, but in order for the font to +work correctly with the \TeX\ software, this constraint should be observed. + + +Following the character preamble is the raster information for the +character, packed by run counts or by bits, as indicated by the flag byte. +If the character is packed by run counts and the required number of nybbles +is odd, then the last byte of the raster description should have a zero +for its least significant nybble. + +@ As an illustration of the \.{PK} format, the character \char4\ from the font +amr10 at 300 dots per inch will be encoded. (Note: amr fonts are obsolete, +and the reference to this character is retained from an older version of +the Computer Modern fonts solely for illustration.) This character was chosen +because it illustrates some +of the borderline cases. The raster for the character looks like this (the +row numbers are chosen for convenience, and are not \MF's row numbers.) + +\vskip\baselineskip +\centerline{\vbox{\baselineskip=10pt +\halign{\hfil#\quad&&\hfil#\hfil\cr +0& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +1& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +2& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +3& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +4& & &M&M& & & & & & & & & & & & & & & & &M&M\cr +5& & &M&M& & & & & & & & & & & & & & & & &M&M\cr +6& & &M&M& & & & & & & & & & & & & & & & &M&M\cr +7\cr +8\cr +9& & & & &M&M& & & & & & & & & & & & &M&M& & \cr +10& & & & &M&M& & & & & & & & & & & & &M&M& & \cr +11& & & & &M&M& & & & & & & & & & & & &M&M& & \cr +12& & & & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M& & \cr +13& & & & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M& & \cr +14& & & & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M& & \cr +15& & & & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M& & \cr +16& & & & &M&M& & & & & & & & & & & & &M&M& & \cr +17& & & & &M&M& & & & & & & & & & & & &M&M& & \cr +18& & & & &M&M& & & & & & & & & & & & &M&M& & \cr +19\cr +20\cr +21\cr +22& & &M&M& & & & & & & & & & & & & & & & &M&M\cr +23& & &M&M& & & & & & & & & & & & & & & & &M&M\cr +24& & &M&M& & & & & & & & & & & & & & & & &M&M\cr +25& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +26& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +27& & &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +28&*& &M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M&M\cr +&\hphantom{M}&\hphantom{M}\cr +}}} +The width of the minimum bounding box for this character is 20; its height +is 29. The `*' represents the reference pixel; notice how it lies outside the +minimum bounding box. The |hoff| value is $-2$, and the |voff| is~28. + +The first task is to calculate the run counts and repeat counts. The repeat +counts are placed at the first transition (black to white or white to black) +in a row, and are enclosed in brackets. White counts are enclosed in +parentheses. It is relatively easy to generate the counts list: +\vskip\baselineskip +\centerline{82 [2] (16) 2 (42) [2] 2 (12) 2 (4) [3]} +\centerline{16 (4) [2] 2 (12) 2 (62) [2] 2 (16) 82} +\vskip\baselineskip +Note that any duplicated rows that are not all white or all black are removed +before the repeat counts are calculated. The rows thus removed are rows 5, 6, +10, 11, 13, 14, 15, 17, 18, 23, and 24. + +@ The next step in the encoding of this character is to calculate the optimal +value of |dyn_f|. The details of how this calculation is done are not +important here; suffice it to say that there is a simple algorithm which in one +pass over the count list can determine the best value of |dyn_f|. For this +character, the optimal value turns out to be 8 (atypically low). Thus, all +count values less than or equal to 8 are packed in one nybble; those from +nine to $(13-8)*16+8$ or 88 are packed in two nybbles. The run encoded values +now become (in hex, separated according to the above list): +\vskip\baselineskip +\centerline{\tt D9 E2 97 2 B1 E2 2 93 2 4 E3} +\centerline{\tt 97 4 E2 2 93 2 C5 E2 2 97 D9} +\vskip\baselineskip\noindent +which comes to 36 nybbles, or 18 bytes. This is shorter than the 73 bytes +required for the bit map, so we use the run count packing. + +@ The short form of the character preamble is used because all of the +parameters fit in their respective lengths. The packet length is therefore +18 bytes for the raster, plus +eight bytes for the character preamble parameters following the character +code, or 26. The |tfm| width for this character is 640796, or {\tt 9C71C} in +hexadecimal. The horizontal escapement is 25 pixels. The flag byte is +88 hex, indicating the short preamble, the black first count, and the +|dyn_f| value of 8. The final total character packet, in hexadecimal, is: +\vskip\baselineskip +$$\vbox{\halign{\hfil #\quad&&{\tt #\ }\cr +Flag byte&88\cr +Packet length&1A\cr +Character code&04\cr +|tfm| width&09&C7&1C\cr +Horizontal escapement (pixels)&19\cr +Width of bit map&14\cr +Height of bit map&1D\cr +Horizontal offset (signed)&FE\cr +Vertical offset&1C\cr +Raster data&D9&E2&97\cr +&2B&1E&22\cr +&93&24&E3\cr +&97&4E&22\cr +&93&2C&5E\cr +&22&97&D9\cr}}$$ + +@ This format was written by Tomas Rokicki in August, 1985. + +@* Input and output. +There are two types of files that this program must deal with---standard +text files and files of bytes (packed files and generic font files.) +For our purposes, we shall consider an eight-bit byte to consist of the +values |0..255|. If your system does not pack these values to a byte, it is +no major difficulty; you must only insure that the input function +|pk_byte| can read packed bytes, and that the output fuunction |gf_byte| +packs the bytes to be shipped. + +@<Types...@>= +@!eight_bits=0..255; {packed file byte} +@!byte_file=packed file of eight_bits ; {for packed file words} +@^system dependancies@> + +@ @<Glob...@>= +@!gf_file,@!pk_file:byte_file; {the I/O streams} +@^system dependencies@> + +@ To prepare these files for input, we |reset| them. An extension of +\PASCAL\ is needed in the case of |gf_file|, since we want to associate +it with external files whose names are specified dynamically (i.e., not +known at compile time). The following code assumes that `|reset(f,s)|' +does this, when |f| is a file variable and |s| is a string variable that +specifies the file name. If |eof(f)| is true immediately after +|reset(f,s)| has acted, we assume that no file named |s| is accessible. +@^system dependencies@> + +@p procedure open_gf_file; {prepares to write packed bytes in a |gf_file|} +begin rewrite(gf_file,gf_name); +gf_loc := 0 ; +end; +@# +procedure open_pk_file; {prepares the input for reading} +begin reset(pk_file,pk_name); +pk_loc := 0 ; +end; + +@ We need a place to store the names of the input and output files, as well +as a byte counter for the output file. + +@<Glob...@>= +@!gf_name,@!pk_name:packed array[1..name_length] of char; {names of input + and output files} +@!gf_loc, @!pk_loc:integer; {how many bytes have we sent?} + +@ We need a procedure that will write a byte to the \.{GF} file. If the +particular system +@^system dependencies@> +requires buffering, here is the place to do it. + +@p procedure gf_byte (i : integer) ; +begin gf_file^ := i ; +put(gf_file) ; +incr(gf_loc) ; +end; + +@ We also need a function that will get a single byte from the \.{PK} file. +Again, buffering may be done in this procedure. + +@p function pk_byte : eight_bits ; +var nybble, temp : eight_bits ; +begin + temp := pk_file^ ; + get(pk_file) ; + pk_loc := pk_loc + 1 ; + pk_byte := temp ; +end ; + +@ Now we are ready to open the files and write the identification of the +pixel file. + +@<Open files@>= +open_pk_file ; +open_gf_file + +@ As we are reading the packed file, we often need to fetch 16 and 32 bit +quantities. Here we have two procedures to do this. + +@p function signed_byte : integer ; +var a : integer ; +begin + a := pk_byte ; + if a > 127 then + a := a - 256 ; + signed_byte := a ; +end ; +@# +function get_16 : integer ; +var a : integer ; +begin + a := pk_byte ; + get_16 := a * 256 + pk_byte ; +end ; +@# +function signed_16 : integer ; +var a : integer ; +begin + a := signed_byte ; + signed_16 := a * 256 + pk_byte ; +end ; +@# +function get_32 : integer ; +var a : integer ; +begin + a := get_16 ; + if a > 32767 then a := a - 65536 ; + get_32 := a * 65536 + get_16 ; +end ; + +@ As we are writing the \.{GF} file, we often need to write signed and +unsigned, one, two, three, and four-byte values. These routines give +us that capability. + +@p procedure gf_sbyte(i : integer) ; +begin + if i < 0 then + i := i + 256 ; + gf_byte(i) ; +end ; +@# +procedure gf_16(i : integer) ; +begin + gf_byte(i div 256) ; + gf_byte(i mod 256) ; +end ; +@# +procedure gf_24(i : integer) ; +begin + gf_byte(i div 65536) ; + gf_16(i mod 65536) ; +end ; +@# +procedure gf_quad(i : integer) ; +begin + if i >= 0 then begin + gf_byte(i div 16777216) ; + end else begin + i := (i + 1073741824) + 1073741824 ; + gf_byte(128 + (i div 16777216)) ; + end ; + gf_24(i mod 16777216) ; +end ; + +@* Character unpacking. +Now we deal with unpacking characters into the \.{GF} representation. + +@<Unpack and write character@>= +dyn_f := flag_byte div 16 ; +flag_byte := flag_byte mod 16 ; +turn_on := flag_byte >= 8 ; +if turn_on then flag_byte := flag_byte - 8 ; +if flag_byte = 7 then + @<Read long character preamble@> +else if flag_byte > 3 then + @<Read extended short character preamble@> +else + @<Read short character preamble@> ; +@<Calculate and check |min_m|, |max_m|, |min_n|, and |max_n|@> ; +@<Save character locator@> ; +@<Write character preamble@> ; +@<Read and translate raster description@> ; +gf_byte(eoc) ; +last_eoc := gf_loc ; +if end_of_packet <> pk_loc then abort('Bad pk file! Bad packet length.') + +@ We need a whole lot of globals used but not defined up there. + +@<Glob...@>= +@!i, @!j : integer ; {index pointers} +@!end_of_packet : integer ; {where we expect the end of the packet to be} +@!dyn_f : integer ; {dynamic packing variable} +@!car : integer ; {the character we are reading} +@!tfm_width : integer ; {the TFM width of the current character} +@!x_off, @!y_off : integer ; {the offsets for the character} + +@ Now we read and check the preamble of the \.{PK} file. In the preamble, we +find the |hppp|, |design_size|, |checksum|. We write the relevant parameters +to the \.{GF} file, including the preamble comment. + +@<Read preamble@>= +if pk_byte <> pk_pre then abort('Bad pk file! pre command missing.') ; +gf_byte(pre) ; +if pk_byte <> pk_id then abort('Wrong version of packed file!.') ; +gf_byte(gf_id_byte) ; +j := pk_byte ; +for i := 1 to j do hppp := pk_byte ; +gf_byte(comm_length) ; +for i := 1 to comm_length do + gf_byte(xord[comment[i]]) ; +design_size := get_32 ; +checksum := get_32 ; +hppp := get_32 ; vppp := get_32 ; +if hppp <> vppp then print_ln('Warning: aspect ratio not 1:1!') ; +magnification := round(hppp * 72.27 * 5 / 65536) ; +last_eoc := gf_loc + +@ Of course, we need to define the above variables. + +@<Glob...@>= +@!comment : packed array[1..comm_length] of char ; +@!magnification : integer ; {resolution at which pixel file is prepared} +@!design_size : integer ; {design size in \.{FIXes}} +@!checksum : integer ; {checksum of pixel file} +@!hppp, @!vppp : integer ; {horizontal and vertical points per inch} + +@ @<Set init...@>= +comment := preamble_comment ; + +@ Now, the character preamble reading modules. First, we have the general +case: the long character preamble format. + +@<Read long character preamble@>= +begin + packet_length := get_32 ; car := get_32 ; + end_of_packet := packet_length + pk_loc ; + tfm_width := get_32 ; + hor_esc := get_32 ; + ver_esc := get_32 ; + c_width := get_32 ; + c_height := get_32 ; + word_width := (c_width + 31) div 32 ; + x_off := get_32 ; + y_off := get_32 ; +end + +@ This module reads the character preamble with double byte parameters. + +@<Read extended short character preamble@>= +begin + packet_length := (flag_byte - 4) * 65536 + get_16 ; + car := pk_byte ; + end_of_packet := packet_length + pk_loc ; + i := pk_byte ; + tfm_width := i * 65536 + get_16 ; + hor_esc := get_16 * 65536 ; + ver_esc := 0 ; + c_width := get_16 ; + c_height := get_16 ; + word_width := (c_width + 31) div 32 ; + x_off := signed_16 ; + y_off := signed_16 ; +end + +@ Here we read the most common character preamble, that with single byte +parameters. + +@<Read short character preamble@>= +begin + packet_length := flag_byte * 256 + pk_byte ; + car := pk_byte ; + end_of_packet := packet_length + pk_loc ; + i := pk_byte ; + tfm_width := i * 65536 + get_16 ; + hor_esc := pk_byte * 65536 ; + ver_esc := 0 ; + c_width := pk_byte ; + c_height := pk_byte ; + word_width := (c_width + 31) div 32 ; + x_off := signed_byte ; + y_off := signed_byte ; +end + +@ Some more globals: + +@<Glob...@>= +@!c_height, @!c_width : integer ; {sizes of the character glyphs} +@!word_width : integer ; {width of character in raster words} +@!hor_esc, @!ver_esc : integer ; {the character escapement} +@!packet_length : integer ; {the length of the packet in bytes} +@!last_eoc : integer ; {the last end of character} + +@ The \.{GF} format requires the minimum and maximum |m| and |n| +values in the postamble, so we generate them here. One thing +that should be noted, here. The value |max_n-min_n| will be the +height of the character glyph, but for the width, you need to +use |max_m-min_m-1|, because of the peculiarities of the \.{GF} +format. + +@<Calculate and check |min_m|, |max_m|, |min_n|, and |max_n|@>= +if (c_height = 0) or (c_width = 0) then begin + c_height := 0 ; c_width := 0 ; x_off := 0 ; y_off := 0 ; +end ; +min_m := - x_off ; +if min_m < mmin_m then + mmin_m := min_m ; +max_m := c_width + min_m ; +if max_m > mmax_m then + mmax_m := max_m ; +min_n := y_off - c_height + 1 ; +max_n := y_off ; +if min_n > max_n then + min_n := max_n ; +if min_n < mmin_n then + mmin_n := min_n ; +if max_n > mmax_n then + mmax_n := max_n + +@ We have to declare the variables which hold the bounding box. We +also need the arrays that hold the back pointers to the characters, +the horizontal and vertical escapements, and the \.{TFM} widths. + +@<Glob...@>= +@!min_m, @!max_m, @!min_n, @!max_n : integer ; +@!mmin_m, @!mmax_m, @!mmin_n, @!mmax_n : integer ; +@!char_pointer, @!s_tfm_width : array [0..255] of integer ; +@!s_hor_esc, @!s_ver_esc : array [0..255] of integer ; +@!this_char_ptr : integer ; + +@ We initialize these bounding box values to be ridiculous, and say +that there were no characters seen yet. + +@<Set init...@>= +mmin_m := 999999 ; +mmin_n := 999999 ; +mmax_m := -999999 ; +mmax_n := -999999 ; +for i := 0 to 255 do + char_pointer[i] := -1 ; + +@ This module takes care of the simple job of writing the character +preamble, after picking one to fit. + +@<Write character preamble@>= +begin + if (char_pointer[car mod 256] = -1) and + (car >= 0) and (car < 256) and + (max_m >= 0) and (max_m < 256) and + (max_n >= 0) and (max_n < 256) and + (max_m >= min_m) and (max_n >= min_n) and + (max_m < min_m + 256) and (max_n < min_n + 256) then begin + char_pointer[car mod 256] := this_char_ptr ; + gf_byte(boc1) ; + gf_byte(car) ; + gf_byte(max_m - min_m) ; + gf_byte(max_m) ; + gf_byte(max_n - min_n) ; + gf_byte(max_n) ; + end else begin + gf_byte(boc) ; + gf_quad(car) ; + gf_quad(char_pointer[car mod 256]) ; + char_pointer[car mod 256] := this_char_ptr ; + gf_quad(min_m) ; + gf_quad(max_m) ; + gf_quad(min_n) ; + gf_quad(max_n) ; + end ; +end + +@ In this routine we either save or check the current character +parameters. + +@<Save character locator@>= +begin + i := car mod 256 ; + if (char_pointer[i] = -1) then begin + s_ver_esc[i] := ver_esc ; + s_hor_esc[i] := hor_esc ; + s_tfm_width[i] := tfm_width ; + end else begin + if (s_ver_esc[i] <> ver_esc) or + (s_hor_esc[i] <> hor_esc) or + (s_tfm_width[i] <> tfm_width) then + print_ln('Two characters mod ', i:1,' have mismatched parameters') ; + end ; +end + +@ And another module to write out those character locators we have so +carefully saved up the information for. + +@<Write character locators@>= +for i := 0 to 255 do + if char_pointer[i] <> -1 then begin + if (s_ver_esc[i] = 0) and (s_hor_esc[i] >= 0) and + (s_hor_esc[i] < 16777216) and (s_hor_esc[i] mod 65536 = 0) then begin + gf_byte(char_loc0) ; + gf_byte(i) ; + gf_byte(s_hor_esc[i] div 65536) ; + end else begin + gf_byte(char_loc) ; + gf_byte(i) ; + gf_quad(s_hor_esc[i]) ; + gf_quad(s_ver_esc[i]) ; + end ; + gf_quad(s_tfm_width[i]) ; + gf_quad(char_pointer[i]) ; + end + +@ Now we have the most important part of the program, where we actually +interpret the commands in the raster description. First of all, we need +a procedure to get a single nybble from the file, as well as one to get +a single bit. We also use the |pk_packed_num| procedure defined in the +\.{PK} file description. + +@p function get_nyb : integer ; +var temp : eight_bits ; +begin + if bit_weight = 0 then begin + input_byte := pk_byte ; + bit_weight := 16 ; + end ; + temp := input_byte div bit_weight ; + input_byte := input_byte - temp * bit_weight ; + bit_weight := bit_weight div 16 ; + get_nyb := temp ; +end ; +@# +function get_bit : boolean ; +var temp : boolean ; +begin + bit_weight := bit_weight div 2 ; + if bit_weight = 0 then begin + input_byte := pk_byte ; + bit_weight := 128 ; + end ; + temp := input_byte >= bit_weight ; + if temp then + input_byte := input_byte - bit_weight ; + get_bit := temp ; +end ; +@<Packed number procedure@> + +@ Now, the globals to help communication between these procedures, and a buffer +for the raster row counts. + +@<Glob...@>= +@!input_byte : eight_bits ; {the byte we are currently decimating} +@!bit_weight : eight_bits ; {weight of the current bit} +@!nybble : eight_bits ; {the current nybble} +@!row_counts : array [0..max_counts] of integer ; + {where the row is constructed} +@!rcp : integer ; { the row counts pointer } + +@ Actually, if the character is a bit mapped character, then we +make it look like run counts by determining the appropriate +values ourselves. Thus, we have a routine which gets the next +count value, below. + +@<Get next count value into |count|@>= +begin + turn_on := not turn_on ; + if dyn_f = 14 then begin + count := 1 ; + done := false ; + while not done do begin + if count_down <= 0 then + done := true + else if (turn_on = get_bit) then + count := count + 1 + else + done := true ; + count_down := count_down - 1 ; + end ; + end else + count := pk_packed_num ; +end + +@ And the main procedure. + +@<Read and translate raster description@>= +if (c_width > 0) and (c_height > 0) then begin + bit_weight := 0 ; + count_down := c_height * c_width - 1 ; + if dyn_f = 14 then + turn_on := get_bit ; + repeat_count := 0 ; + x_to_go := c_width ; + y_to_go := c_height ; + cur_n := c_height ; + count := 0 ; + first_on := turn_on ; + turn_on := not turn_on ; + rcp := 0 ; + while y_to_go > 0 do begin + if count = 0 then + @<Get next count...@> ; + if rcp = 0 then + first_on := turn_on ; + while count >= x_to_go do begin + row_counts[rcp] := x_to_go ; + count := count - x_to_go ; + for i := 0 to repeat_count do begin + @<Output row@> ; + y_to_go := y_to_go - 1 ; + end ; + repeat_count := 0 ; + x_to_go := c_width ; + rcp := 0 ; + if (count > 0) then + first_on := turn_on ; + end ; + if count > 0 then begin + row_counts[rcp] := count ; + if rcp = 0 then + first_on := turn_on ; + rcp := rcp + 1 ; + if rcp > max_counts then begin + print_ln('A character had too many run counts') ; + jump_out ; + end ; + x_to_go := x_to_go - count ; + count := 0 ; + end ; + end ; +end + +@ This routine actually outputs a row to the \.{GF} file. + +@<Output row@>= +if (rcp > 0) or first_on then begin + j := 0 ; + max := rcp ; + if not turn_on then + max := max - 1 ; + if cur_n - y_to_go = 1 then begin + if first_on then + gf_byte(new_row_0) + else if row_counts[0] < 165 then begin + gf_byte(new_row_0 + row_counts[0]) ; + j := j + 1 ; + end else + gf_byte(skip0) ; + end else if cur_n > y_to_go then begin + if cur_n - y_to_go < 257 then begin + gf_byte(skip1) ; + gf_byte(cur_n - y_to_go - 1) ; + end else begin + gf_byte(skip1+1) ; + gf_16(cur_n - y_to_go - 1) ; + end ; + if first_on then + gf_byte(paint_0) ; + end else if first_on then + gf_byte(paint_0) ; + cur_n := y_to_go ; + while j <= max do begin + if row_counts[j] < 64 then + gf_byte(paint_0 + row_counts[j]) + else if row_counts[j] < 256 then begin + gf_byte(paint1) ; + gf_byte(row_counts[j]) ; + end else begin + gf_byte(paint1+1) ; + gf_16(row_counts[j]) ; + end ; + j := j + 1 ; + end ; +end + +@ Here we need the array which counts down the number of bits, and +the current state flag. + +@<Glob...@>= +@!count_down : integer ; { have we run out of bits yet? } +@!done : boolean ; { are we done yet? } +@!max : integer ; { the maximum number of counts to output } +@!repeat_count : integer ; {how many times to repeat the next row?} +@!x_to_go, @!y_to_go : integer ; {how many columns/rows left?} +@!turn_on, @!first_on : boolean ; {are we black here?} +@!count : integer ; {how many bits of current color left?} +@!cur_n : integer ; {what row are we at?} + +@ To finish the \.{GF} file, we write out a postamble, including the +character locators that we stored away. + +@<Write \.{GF} postamble@>= +j := gf_loc ; +gf_byte(post) ; +gf_quad(last_eoc) ; +gf_quad(design_size) ; +gf_quad(checksum) ; +gf_quad(hppp) ; +gf_quad(vppp) ; +gf_quad(mmin_m) ; +gf_quad(mmax_m) ; +gf_quad(mmin_n) ; +gf_quad(mmax_n) ; +@<Write character locators@> ; +gf_byte(post_post) ; +gf_quad(j) ; +gf_byte(gf_id_byte) ; +for i := 0 to 3 do + gf_byte(223) ; +while gf_loc mod 4 <> 0 do + gf_byte(223) + +@ We need the |flag_byte| variable. + +@<Glob...@>= +@!flag_byte : integer ; {command or character flag byte} + +@ Another necessary procedure skips over any specials between characters +and before and after the postamble. (It echoes the specials exactly.) + +@p procedure skip_specials ; +var i, j, k : integer ; +begin + this_char_ptr := gf_loc ; + repeat + flag_byte := pk_byte ; + if flag_byte >= 240 then + case flag_byte of + 240, 241, 242, 243 : +begin + i := 0 ; + gf_byte(flag_byte-1) ; + for j := 240 to flag_byte do begin + k := pk_byte ; + gf_byte(k) ; + i := 256 * i + k ; + end ; + for j := 1 to i do gf_byte(pk_byte) ; +end ; + 244 : +begin + gf_byte(243) ; + gf_quad(get_32) ; +end ; + 245 : begin end ; + 246 : begin end ; + 247, 248, 249, 250, 251, 252, 253, 254, 255 : + abort('Unexpected ', flag_byte:1,'!') ; + endcases ; + until (flag_byte < 240) or (flag_byte = pk_post) ; +end ; + +@* Terminal communication. +We must get the file names and determine whether input is to be in +hexadecimal or binary. To do this, we use the standard input path +name. We need a procedure to flush the input buffer. For most systems, +this will be an empty statement. For other systems, a |print_ln| will +provide a quick fix. We also need a routine to get a line of input from +the terminal. On some systems, a simple |read_ln| will do. Finally, +a macro to print a string to the first blank is required. + +@d flush_buffer == begin end +@d get_line(#) == if eoln(input) then read_ln(input) ; + i := 1 ; + while not (eoln(input) or eof(input)) do begin + #[i] := input^ ; + incr(i) ; + get(input) ; + end ; + #[i] := ' ' + +@ @p procedure dialog ; +var i : integer ; {index variable} +buffer : packed array [1..name_length] of char; {input buffer} +begin + for i := 1 to name_length do begin + gf_name[i] := ' ' ; + pk_name[i] := ' ' ; + end; + print('Input file name: ') ; + flush_buffer ; + get_line(pk_name) ; + print('Output file name: ') ; + flush_buffer ; + get_line(gf_name) ; +end ; + +@* The main program. +Now that we have all the pieces written, let us put them together. + +@p begin +initialize ; +dialog ; +@<Open files@> ; +@<Read preamble@> ; +skip_specials ; +while flag_byte <> pk_post do begin + @<Unpack and write character@> ; + skip_specials ; +end ; +while not eof(pk_file) do i := pk_byte ; +@<Write \.{GF} postamble@> ; +print_ln(pk_loc:1,' bytes unpacked to ',gf_loc:1,' bytes.'); +final_end : +end . + +@* System-dependent changes. +This section should be replaced, if necessary, by changes to the program +that are necessary to make \.{PKtoGF} work at a particular installation. +Any additional routines should be inserted here. +@^system dependencies@> + +@* Index. +Pointers to error messages appear here together with the section numbers +where each ident\-i\-fier is used. |