path: root/Build/source/texk/dvipng/dvipng.1

.\" Automatically generated by Pod::Man v1.37, Pod::Parser v1.32
.\"
.\" Standard preamble:
.\" ========================================================================
.de Sh \" Subsection heading
.br
.if t .Sp
.ne 5
.PP
\fB\\$1\fR
.PP
..
.de Sp \" Vertical space (when we can't use .PP)
.if t .sp .5v
.if n .sp
..
.de Vb \" Begin verbatim text
.ft CW
.nf
.ne \\$1
..
.de Ve \" End verbatim text
.ft R
.fi
..
.\" Set up some character translations and predefined strings.  \*(-- will
.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left
.\" double quote, and \*(R" will give a right double quote.  \*(C+ will
.\" give a nicer C++.  Capital omega is used to do unbreakable dashes and
.\" therefore won't be available.  \*(C` and \*(C' expand to `' in nroff,
.\" nothing in troff, for use with C<>.
.tr \(*W-
.ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p'
.ie n \{\
.    ds -- \(*W-
.    ds PI pi
.    if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch
.    if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\"  diablo 12 pitch
.    ds L" ""
.    ds R" ""
.    ds C` ""
.    ds C' ""
'br\}
.el\{\
.    ds -- \|\(em\|
.    ds PI \(*p
.    ds L" ``
.    ds R" ''
'br\}
.\"
.\" If the F register is turned on, we'll generate index entries on stderr for
.\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index
.\" entries marked with X<> in POD.  Of course, you'll have to process the
.\" output yourself in some meaningful fashion.
.if \nF \{\
.    de IX
.    tm Index:\\$1\t\\n%\t"\\$2"
..
.    nr % 0
.    rr F
.\}
.\"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.hy 0
.if n .na
.\"
.\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2).
.\" Fear.  Run.  Save yourself.  No user-serviceable parts.
.    \" fudge factors for nroff and troff
.if n \{\
.    ds #H 0
.    ds #V .8m
.    ds #F .3m
.    ds #[ \f1
.    ds #] \fP
.\}
.if t \{\
.    ds #H ((1u-(\\\\n(.fu%2u))*.13m)
.    ds #V .6m
.    ds #F 0
.    ds #[ \&
.    ds #] \&
.\}
.    \" simple accents for nroff and troff
.if n \{\
.    ds ' \&
.    ds ` \&
.    ds ^ \&
.    ds , \&
.    ds ~ ~
.    ds /
.\}
.if t \{\
.    ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u"
.    ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u'
.    ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u'
.    ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u'
.    ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u'
.    ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u'
.\}
.    \" troff and (daisy-wheel) nroff accents
.ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V'
.ds 8 \h'\*(#H'\(*b\h'-\*(#H'
.ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#]
.ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H'
.ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u'
.ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#]
.ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#]
.ds ae a\h'-(\w'a'u*4/10)'e
.ds Ae A\h'-(\w'A'u*4/10)'E
.    \" corrections for vroff
.if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u'
.if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u'
.    \" for low resolution devices (crt and lpr)
.if \n(.H>23 .if \n(.V>19 \
\{\
.    ds : e
.    ds 8 ss
.    ds o a
.    ds d- d\h'-1'\(ga
.    ds D- D\h'-1'\(hy
.    ds th \o'bp'
.    ds Th \o'LP'
.    ds ae ae
.    ds Ae AE
.\}
.rm #[ #] #H #V #F C
.\" ========================================================================
.\"
.IX Title "DVIPNG 1"
.TH DVIPNG 1 "2006-11-07" "dvipng 1.9" "User commands"
.SH "NAME"
dvipng \- A DVI\-to\-PNG translator
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
dvipng [options] filename
.PP
dvipng [options] [filename] \-
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
This program makes \s-1PNG\s0 and/or \s-1GIF\s0 graphics from \s-1DVI\s0 files as obtained
from TeX and its relatives. 
.PP
If \s-1GIF\s0 support is enabled, \s-1GIF\s0 output is chosen by using the
\&\fBdvigif\fR binary or with the \fB\-\-gif\fR option.
.PP
The benefits of \fBdvipng\fR/\fBdvigif\fR include
.IP "\(bu" 4
Speed. It is a very fast bitmap-rendering code for \s-1DVI\s0 files, which
makes it suitable for generating large amounts of images on\-the\-fly,
as needed in preview\-latex, WeBWorK and others.
.IP "\(bu" 4
It does not read the postamble, so it can be started before TeX
finishes. There is a \fB\-\-follow\fR switch that makes dvipng wait at
end-of-file for further output, unless it finds the \s-1POST\s0 marker that
indicates the end of the \s-1DVI\s0.
.IP "\(bu" 4
Interactive query of options. dvipng can read options interactively
through stdin, and all options are usable. It is even possible to change
the input file through this interface.
.IP "\(bu" 4
Supports \s-1PK\s0, \s-1VF\s0, PostScript Type1, and TrueType fonts, subfonts (i.e.,
as used in CJK\-LaTeX), color specials, and inclusion of PostScript,
\&\s-1PNG\s0, \s-1JPEG\s0 or \s-1GIF\s0 images.
.IP "\(bu" 4
and more...
.SH "OPTIONS"
.IX Header "OPTIONS"
Many of the parameterless options listed here can be turned off by
suffixing the option with a zero (\fB0\fR); for instance, to turn off
page reversal, use \fB\-r0\fR.  Such options are marked with a trailing
\&\fB*\fR.
.IP "\fB\-\fR" 4
.IX Item "-"
Read additional options from standard input after processing the command
line.
.IP "\fB\-\-help\fR" 4
.IX Item "--help"
Print a usage message and exit.
.IP "\fB\-\-version\fR" 4
.IX Item "--version"
Print the version number and exit.
.IP "\fB\-bd\fR \fInum\fR" 4
.IX Item "-bd num"
.PD 0
.IP "\fB\-bd\fR \fIcolor_spec\fR" 4
.IX Item "-bd color_spec"
.IP "\fB\-bd '\fR\fInum\fR\fB \fR\fIcolor_spec\fR\fB'\fR" 4
.IX Item "-bd 'num color_spec'"
.PD
Set the pixel width of the transparent border (default 0). Using this
option will make the image edges transparent, but it only affects pixels
with the background color. Giving a \fIcolor_spec\fR will set the
fallback color, to be used in viewers that cannot handle transparency
(the default is the background color). The color spec should be in
TeX color \especial syntax, e.g., 'rgb 1.0 0.0 0.0'. Setting the
fallback color makes the default border width 1 px. 
.IP "\fB\-\-bdpi\fR \fInum\fR" 4
.IX Item "--bdpi num"
Set the base (Metafont) resolution, both horizontal and vertical, to
\&\fInum\fR dpi (dots per inch). This option is necessary when manually
selecting Metafont mode with the \-\-mode option (see below).
.IP "\fB\-bg\fR \fIcolor_spec\fR" 4
.IX Item "-bg color_spec"
Choose background color for the images. This option will be ignored if
there is a background color \especial in the \s-1DVI\s0. The color spec should
be in TeX color \especial syntax, e.g., 'rgb 1.0 0.0 0.0'. You can
also specify 'Transparent' or 'transparent' which will give you a
transparent background with the normal background as a fallback color. A
capitalized 'Transparent' will give a full-alpha transparency, while an
all-lowercase 'transparent' will give a simple fully transparent
background with non-transparent antialiased pixels. The latter would be
suitable for viewers who cannot cope with a true alpha channel.  \s-1GIF\s0
images do not support full alpha transparency, so in case of \s-1GIF\s0 output,
both variants will use the latter behaviour.  
.IP "\fB\-d\fR \fInum\fR" 4
.IX Item "-d num"
Set the debug flags, showing what dvipng (thinks it) is doing. This will
work unless dvipng has been compiled without the \f(CW\*(C`DEBUG\*(C'\fR option
(not recommended). Set the flags as you need them, use \fB\-d \-1\fR as
the first option for maximum output.  
.IP "\fB\-D\fR \fInum\fR" 4
.IX Item "-D num"
Set the output resolution, both horizontal and vertical, to \fInum\fR
dpi (dots per inch). 
.Sp
One may want to adjust this to fit a certain text font size (e.g., on
a web page), and for a text font height of \fIfont_px\fR pixels (in
Mozilla) the correct formula is
.Sp
.Vb 1
\&        <dpi> = <font_px> * 72.27 / 10 [px * TeXpt/in / TeXpt]
.Ve
.Sp
The last division by ten is due to the standard font height 10pt in
your document, if you use 12pt, divide by 12. Unfortunately, some
proprietary browsers have font height in pt (points), not pixels. You
have to rescale that to pixels, using the screen resolution (default
is usually 96 dpi) which means the formula is
.Sp
.Vb 1
\&        <font_px> = <font_pt> * 96 / 72 [pt * px/in / (pt/in)]
.Ve
.Sp
On some high-res screens, the value is instead 120 dpi. Good luck!
.IP "\fB\-\-depth*\fR" 4
.IX Item "--depth*"
Report the depth of the image. This only works reliably when the
LaTeX style \fIpreview.sty\fR from preview-latex is used. It
reports the number of pixels from the bottom of the image to the
baseline of the image. This can be used for vertical positioning of the
image in, e.g., web documents, where one would use (Cascading
StyleSheets 1)
.Sp
.Vb 1
\&        <IMG SRC="<filename.png>" STYLE="vertical\-align: \-<depth>px">
.Ve
.Sp
The depth is a negative offset in this case, so the minus sign is
necessary, and the unit is pixels (px).
.IP "\fB\-\-dvinum*\fR" 4
.IX Item "--dvinum*"
Set this option to make the output page number be the TeX page
numbers rather than the physical page number. See the \fB\-o\fR switch.
.IP "\fB\-fg\fR \fIcolor_spec\fR" 4
.IX Item "-fg color_spec"
Choose foreground color for the images. This option will be ignored if
there is a foreground color \especial in the \s-1DVI\s0. The color spec should
be in TeX color \especial syntax, e.g., 'rgb 1.0 0.0 0.0'.
.IP "\fB\-\-follow*\fR" 4
.IX Item "--follow*"
Wait for data at end\-of\-file. One of the benefits of dvipng is that it
does not read the postamble, so it can be started before TeX
finishes. This switch makes dvipng wait at end-of-file for further
output, unless it finds the \s-1POST\s0 marker that indicates the end of the
\&\s-1DVI\s0. This is similar to \fBtail \-f\fR but for DVI-to-PNG conversion.
.IP "\fB\-\-freetype*\fR" 4
.IX Item "--freetype*"
Enable/disable FreeType font rendering (default on). This option is
available if the FreeType2 font library was present at compilation time.
If this is the case, dvipng will have direct support for PostScript
Type1 and TrueType fonts internally, rather than using \fBgsftopk\fR
for rendering the fonts. If you have PostScript versions of Computer
Modern installed, there will be no need to generate bitmapped variants
on disk of these. Then, you can render images at different (and unusual)
resolutions without cluttering the disk with lots of bitmapped fonts.
Note that if you have both FreeType and T1lib on your system, FreeType
will be preferred by dvipng. If you for some reason would want to use
T1lib rendering, use this option.
.IP "\fB\-\-gamma\fR \fInum\fR" 4
.IX Item "--gamma num"
Control the interpolation of colors in the greyscale anti-aliasing
color palette.  Default value is 1.0.  For 0 < \fInum\fR < 1, the
fonts will be lighter (more like the background), and for \fInum\fR >
1, the fonts will be darker (more like the foreground).
.IP "\fB\-\-gif*\fR" 4
.IX Item "--gif*"
The images are output in the \s-1GIF\s0 format, if \s-1GIF\s0 support is enabled.
This is the default for the \fBdvigif\fR binary, which only will be
available when \s-1GIF\s0 support is enabled. \s-1GIF\s0 images are palette images
(see the \fB\-\-palette\fR option) and does not support true alpha
channels (see the \fB\-\-bg\fR option). See also the \fB\-\-png\fR
option.
.IP "\fB\-\-height*\fR" 4
.IX Item "--height*"
Report the height of the image. This only works reliably when the
LaTeX style \fIpreview.sty\fR from preview-latex is used. It
reports the number of pixels from the top of the image to the
baseline of the image. The total height of the image is obtained as the
sum of the values reported from \fB\-\-height\fR and \fB\-\-depth\fR.
.IP "\fB\-l [=]\fR\fInum\fR" 4
.IX Item "-l [=]num"
The last page printed will be the first one numbered \fInum\fR. Default
is the last page in the document.  If \fInum\fR is prefixed by an equals
sign, then it (and the argument to the \fB\-p\fR option, if specified)
is treated as a physical (absolute) page number, rather than a value to
compare with the TeX \fB\ecount0\fR values stored in the \s-1DVI\s0 file.
Thus, using \fB\-l =9\fR will end with the ninth page of the document,
no matter what the pages are actually numbered.
.IP "\fB\-\-mode\fR \fImode\fR" 4
.IX Item "--mode mode"
Use \fImode\fR as the Metafont device name for the \s-1PK\s0 fonts (both for
path searching and font generation). This needs to be augmented with the
base device resolution, given with the \fB\-\-bdpi\fR option. See the
file <\fBftp://ftp.tug.org/tex/modes.mf\fR> for a list of resolutions and
mode names for most devices. 
.IP "\fB\-M*\fR" 4
.IX Item "-M*"
Turns off automatic \s-1PK\s0 font generation (\fImktexpk\fR). This will have
no effect when using PostScript fonts, since no \s-1PK\s0 font generation will
be done anyway.
.IP "\fB\-\-noghostscript*\fR" 4
.IX Item "--noghostscript*"
This switch prohibits the internal call to GhostScript for displaying
PostScript specials. \fB\-\-noghostscript0\fR turns the call back on.
.IP "\fB\-\-nogssafer*\fR" 4
.IX Item "--nogssafer*"
Normally, if GhostScript is used to render PostScript specials, the
GhostScript interpreter is run with the option \fB\-dSAFER\fR. The
\&\fB\-\-nogssafer\fR option runs GhostScript without \fB\-dSAFER\fR. The
\&\fB\-dSAFER\fR option in Ghostscript disables PostScript operators such
as deletefile, to prevent possibly malicious PostScript programs from
having any effect.
.IP "\fB\-o\fR \fIname\fR" 4
.IX Item "-o name"
Send output to the file \fIname\fR. A single occurrence of \fB%d\fR or
\&\fB%01d\fR, ..., \fB%09d\fR will be exchanged for the physical
page number (this can be changed, see the \fB\-\-dvinum\fR switch). The
default output filename is \fIfile\fR\fB%d.png\fR where the input \s-1DVI\s0
file was \fIfile\fR\fB.dvi\fR.
.IP "\fB\-O\fR \fIx\-offset\fR\fB,\fR\fIy\-offset\fR" 4
.IX Item "-O x-offset,y-offset"
Move the origin by \fIx\-offset\fR,\fIy\-offset\fR, a comma-separated
pair of dimensions such as \fB.1in,\-.3cm\fR.
The origin of the page is shifted from the default position
(of one inch down, one inch to the right from the upper left corner of
the paper) by this amount.  
.IP "\fB\-p [=]\fR\fInum\fR" 4
.IX Item "-p [=]num"
The first page printed will be the first one numbered \fInum\fR. Default
is the first page in the document.  If \fInum\fR is prefixed by an
equals sign, then it (and the argument to the \fB\-l\fR option, if
specified) is treated as a physical (absolute) page number, rather than
a value to compare with the TeX \fB\ecount0\fR values stored in the
\&\s-1DVI\s0 file.  Thus, using \fB\-p =3\fR will start with the third page of
the document, no matter what the pages are actually numbered.
.IP "\fB\-\-palette*\fR" 4
.IX Item "--palette*"
Starting from \fBdvipng\fR 1.8, the output \s-1PNG\s0 will be a truecolor
png when an external image is included, to avoid unnecessary delay and
quality reduction, and enable the \s-1EPS\s0 translator to draw on a
transparent background and outside of the boundingbox. This switch
will force palette (256\-color) output and make \fBdvipng\fR revert to
the old behaviour, where included images were opaque and always
clipped to the boundingbox. This will also override the
\&\fB\-\-truecolor\fR switch if present.
.IP "\fB\-\-picky*\fR" 4
.IX Item "--picky*"
No images are output when a warning occurs. Normally, dvipng will
output an image in spite of a warning, but there may be something
missing in this image. One reason to use this option would be if you
have a more complete but slower fallback converter. Mainly, this is
useful for failed figure inclusion and unknown \especial occurrences,
but warnings will also occur for missing or unknown color specs and
missing \s-1PK\s0 fonts.
.IP "\fB\-\-png*\fR" 4
.IX Item "--png*"
The images are output in the \s-1PNG\s0 format. This is the default for the
\&\fBdvipng\fR binary. See also the \fB\-\-gif\fR option.
.IP "\fB\-pp\fR \fIfirstpage\fR\fB\-\fR\fIlastpage\fR" 4
.IX Item "-pp firstpage-lastpage"
Print pages \fIfirstpage\fR through \fIlastpage\fR; but not quite
equivalent to \fB\-p\fR \fIfirstpage\fR \fB\-l\fR \fIlastpage\fR. For example,
when rendering a book, there may be several instances of a page in the
\&\s-1DVI\s0 file (one in \f(CW\*(C`\efrontmatter\*(C'\fR, one in \f(CW\*(C`\emainmatter\*(C'\fR, and one
in \f(CW\*(C`\ebackmatter\*(C'\fR). In case of several pages matching, \fB\-pp\fR
\&\fIfirstpage\fR\fB\-\fR\fIlastpage\fR will render \fIall\fR pages that
matches the specified range, while \fB\-p\fR \fIfirstpage\fR \fB\-l\fR
\&\fIlastpage\fR will render the pages from the \fIfirst\fR occurrence
of \fIfirstpage\fR to the \fIfirst\fR occurrence of \fIlastpage\fR.
This is the (undocumented) behaviour of dvips. In dvipng you can give
both kinds of options, in which case you get all pages that matches the
range in \fB\-pp\fR between the pages from \fB\-p\fR to \fB\-l\fR. Also
multiple \fB\-pp\fR options accumulate, unlike \fB\-p\fR and \fB\-l\fR.
The \fB\-\fR separator can also be \fB:\fR. Note that \fB\-pp \-1\fR
will be interpreted as \*(L"all pages up to and including 1\*(R", if you want a
page numbered \-1 (only the table of contents, say) put \fB\-pp \-1\-\-1\fR,
or more readable, \fB\-pp \-1:\-1\fR.
.IP "\fB\-q*\fR" 4
.IX Item "-q*"
Run quietly.  Don't chatter about pages converted, etc. to standard
output; report no warnings (only errors) to standard error.
.IP "\fB\-Q\fR \fInum\fR" 4
.IX Item "-Q num"
Set the quality to \fInum\fR. That is, choose the number of antialiasing
levels for \s-1PK\s0 and T1lib rendering to be \fInum\fR*\fInum\fR+1. The default
value is 4 which gives 17 levels of antialiasing for antialiased fonts
from these two. If FreeType is available, its rendering is unaffected by
this option.
.IP "\fB\-r*\fR" 4
.IX Item "-r*"
Toggle output of pages in reverse/forward order. By default, the first
page in the \s-1DVI\s0 is output first.
.IP "\fB\-\-strict*\fR" 4
.IX Item "--strict*"
The program exits when a warning occurs. Normally, dvipng will output
an image in spite of a warning, but there may be something missing in
this image. One reason to use this option would be if you have a more
complete but slower fallback converter. See the \fB\-\-picky\fR option
above for a list of when warnings occur.
.IP "\fB\-T\fR \fIimage_size\fR" 4
.IX Item "-T image_size"
Set the image size to \fIimage_size\fR which can be either of
\&\fBbbox\fR, \fBtight\fR, or a comma-separated pair of dimensions
\&\fIhsize\fR,\fIvsize\fR such as \fB.1in,.3cm\fR. The default is
\&\fBbbox\fR which produces a \s-1PNG\s0 that includes all ink put on the page
and in addition the \s-1DVI\s0 origin, located 1in from the top and 1in from
the left edge of the paper. This usually gives whitespace above and to
the left in the produced image. The value \fBtight\fR will make dvipng
only include all ink put on the page, producing neat images.
.IP "\fB\-\-t1lib*\fR" 4
.IX Item "--t1lib*"
Enable/disable T1lib font rendering (default on). This option is
available if the T1lib font library was present at compilation time. If
this is the case, dvipng will have direct support for PostScript Type1
fonts internally, rather than using \fBgsftopk\fR for rendering the
fonts. If you have PostScript versions of Computer Modern installed,
there will be no need to generate bitmapped variants on disk of these.
Then, you can render images at different (and unusual) resolutions
without cluttering the disk with lots of bitmapped fonts. Note that if
you have both FreeType and T1lib on your system FreeType will be
preferred by dvipng, and if you for some reason rather want to use
T1lib, give the option \fB\-\-freetype0\fR (see above).
.IP "\fB\-\-truecolor*\fR" 4
.IX Item "--truecolor*"
This will make \fBdvipng\fR generate truecolor output. Note that
truecolor output is automatic if you include an external image in your
\&\s-1DVI\s0, e.g., via a PostScript special (i.e., the \fBgraphics\fR or
\&\fBgraphicx\fR package). This switch is overridden by the
\&\fB\-\-palette\fR switch.
.IP "\fB\-v*\fR" 4
.IX Item "-v*"
Enable verbose operation. This will currently indicate what fonts is
used, in addition to the usual output.
.IP "\fB\-x\fR \fInum\fR" 4
.IX Item "-x num"
Set the x magnification ratio to \fInum\fR/1000. Overrides
the magnification specified in the \s-1DVI\s0 file.  Must be between 10 and
100000.  It is recommended that you use standard magstep values (1095,
1200, 1440, 1728, 2074, 2488, 2986, and so on) to help reduce the total
number of \s-1PK\s0 files generated.  \fInum\fR may be a real number, not an
integer, for increased precision.
.IP "\fB\-z\fR \fInum\fR" 4
.IX Item "-z num"
Set the \s-1PNG\s0 compression level to \fInum\fR. This option is enabled if
your \fBlibgd\fR is new enough. The default compression level is 1,
which selects maximum speed at the price of slightly larger PNGs. For an
older \fBlibgd\fR, the hard-soldered value 5 is used. The include file
\&\fBpng.h\fR says
\&\*(L"Currently, valid values range from 0 \- 9, corresponding directly to
the zlib compression levels 0 \- 9 (0 \- no compression, 9 \- \*(R"maximal\*(L"
compression). Note that tests have shown that zlib compression levels
3\-6 usually perform as well as level 9 for \s-1PNG\s0 images, and do
considerably fewer calculations. In the future, these values may not
correspond directly to the zlib compression levels.\*(R"
.SH "NOTES"
.IX Header "NOTES"
The full manual is accessible in the info format, on most systems by typing
.PP
.Vb 1
\&        info dvipng
.Ve
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
This program is released under the \s-1GNU\s0 General Public License, see the
\&\s-1COPYING\s0 file in the dvipng distribution or
<\fBhttp://www.gnu.org/licenses/gpl.html\fR>.
.PP
Copyright (c) 2002\-2006 Jan-AAke Larsson