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%! viewjpeg.ps Copyright (C) 1994 Thomas Merz <tm@pdflib.com>
%
% This software is provided AS-IS with no warranty, either express or
% implied.
%
% This software is distributed under license and may not be copied,
% modified or distributed except as expressly authorized under the terms
% of the license contained in the file LICENSE in this distribution.
%
% For more information about licensing, please refer to
% http://www.ghostscript.com/licensing/. For information on
% commercial licensing, go to http://www.artifex.com/licensing/ or
% contact Artifex Software, Inc., 101 Lucas Valley Road #110,
% San Rafael, CA 94903, U.S.A., +1(415)492-9861.
% $Id: viewjpeg.ps 6300 2005-12-28 19:56:24Z giles $
% View JPEG files with Ghostscript
%
% This PostScript code relies on level 2 features.
%
% Only JPEG baseline, extended sequential, and progressive files
% are supported. Note that Adobe PostScript level 2 does not include
% progressive-JPEG support. Ghostscript with IJG JPEG v6 or later
% will decode progressive JPEG, but only if you edit gsjmorec.h to
% enable that feature.
%
% Author's address:
% ------------------------------+
% {(pstack exec quit) = flush } | Thomas Merz, Munich
% pstack exec quit | voice +49/89/29160728
% ------------------------------+ tm@muc.de http://www.muc.de/~tm/
%
% $Id: viewjpeg.ps 6300 2005-12-28 19:56:24Z giles $
% Updated by L. Peter Deutsch 20-May-1997:
% move the usage example to the beginning
% Updates by Tom Lane 6-Sep-1995
% Usage example:
% (jpeg-6/testimg.jpg) viewJPEG
/languagelevel where {pop languagelevel 2 lt}{true} ifelse {
(JPEG needs PostScript Level 2!\n) print flush stop
} if
/JPEGdict 20 dict def
JPEGdict begin
/NoParamMarkers [ % JPEG markers without additional parameters
16#D0 16#D1 16#D2 16#D3 16#D4 16#D5 16#D6 16#D7 16#D8 16#01
] def
/NotSupportedMarkers [ % JPEG markers not supported by PostScript level 2
16#C3 16#C5 16#C6 16#C7 16#C8 16#C9 16#CA 16#CB 16#CD 16#CE 16#CF
] def
% Names of color spaces
/ColorSpaceNames << /1 /DeviceGray /3 /DeviceRGB /4 /DeviceCMYK >> def
% read one byte from file F
% - ==> int --or-- stop context
/NextByte {
F read not { (Read error in ViewJPEG!\n) print flush stop } if
} bind def
/SkipSegment { % read two bytes and skip that much data
NextByte 8 bitshift NextByte add 2 sub { NextByte pop } repeat
} bind def
% read width, height, and # of components from JPEG markers
% and store in dict
/readJPEGmarkers { % - ==> dict --or-- stop context
5 dict begin
{ % loop: read JPEG marker segments until we find SOFn marker or EOF
NextByte
16#FF eq { % found marker
/markertype NextByte def
% Is it S0F0=baseline, SOF1=extended sequential, SOF2=progressive ?
markertype dup 16#C0 ge exch 16#C2 le and {
NextByte pop NextByte pop % segment length
% Ghostscript and Adobe PS accept only data precision 8
NextByte 8 ne {
(Error: not 8 bits per component!\n) print flush stop
} if
% Read crucial image parameters
/height NextByte 8 bitshift NextByte add def
/width NextByte 8 bitshift NextByte add def
/colors NextByte def
VJPGDEBUG { currentdict { exch == == } forall flush } if
exit
} if
% detect several segment types which are not compatible with PS
NotSupportedMarkers {
markertype eq {
(Marker ) print markertype ==
(not supported!\n) print flush stop
} if
} forall
% Skip segment if marker has parameters associated with it
true NoParamMarkers { markertype eq {pop false exit} if } forall
{ SkipSegment } if
} if
} loop
currentdict dup /markertype undef
end
} bind def
end % JPEGdict
% read image parameters from JPEG file and display the image
/viewJPEG { % <file|string> ==> -
save
JPEGdict begin
/saved exch def
/scratch 1 string def
dup type /stringtype eq { (r) file } if
/F exch def
readJPEGmarkers begin
F 0 setfileposition % reset file pointer
% We use the whole clipping area for the image (at least in one dimension)
gsave clippath pathbbox grestore
/ury exch def /urx exch def
/lly exch def /llx exch def
llx lly translate
width height scale
% use whole width or height, whichever is appropriate
urx llx sub width div ury lly sub height div
2 copy gt { exch } if pop % min
dup scale
ColorSpaceNames colors scratch cvs get setcolorspace
% prepare image dictionary
<< /ImageType 1
/Width width
/Height height
/ImageMatrix [ width 0 0 height neg 0 height ]
/BitsPerComponent 8
% If 4-component (CMYK), assume data is inverted per Adobe Photoshop
colors 4 eq {
/Decode [ colors { 1 0 } repeat ]
} {
/Decode [ colors { 0 1 } repeat ]
} ifelse
/DataSource F /DCTDecode filter
>> image
end % image parameter dictionary
saved end restore
} bind def
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