160 lines
4.8 KiB
PostScript
160 lines
4.8 KiB
PostScript
%! viewjpeg.ps Copyright (C) 1994 Thomas Merz <tm@pdflib.com>
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%
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% This software is provided AS-IS with no warranty, either express or
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% implied.
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%
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% This software is distributed under license and may not be copied,
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% modified or distributed except as expressly authorized under the terms
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% of the license contained in the file LICENSE in this distribution.
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%
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% For more information about licensing, please refer to
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% http://www.ghostscript.com/licensing/. For information on
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% commercial licensing, go to http://www.artifex.com/licensing/ or
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% contact Artifex Software, Inc., 101 Lucas Valley Road #110,
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% San Rafael, CA 94903, U.S.A., +1(415)492-9861.
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% $Id: viewjpeg.ps,v 1.6 2003/04/12 18:08:18 ray Exp $
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% View JPEG files with Ghostscript
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%
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% This PostScript code relies on level 2 features.
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%
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% Only JPEG baseline, extended sequential, and progressive files
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% are supported. Note that Adobe PostScript level 2 does not include
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% progressive-JPEG support. Ghostscript with IJG JPEG v6 or later
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% will decode progressive JPEG, but only if you edit gsjmorec.h to
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% enable that feature.
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%
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% Author's address:
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% ------------------------------+
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% {(pstack exec quit) = flush } | Thomas Merz, Munich
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% pstack exec quit | voice +49/89/29160728
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% ------------------------------+ tm@muc.de http://www.muc.de/~tm/
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%
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% $Id: viewjpeg.ps,v 1.6 2003/04/12 18:08:18 ray Exp $
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% Updated by L. Peter Deutsch 20-May-1997:
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% move the usage example to the beginning
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% Updates by Tom Lane 6-Sep-1995
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% Usage example:
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% (jpeg-6/testimg.jpg) viewJPEG
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/languagelevel where {pop languagelevel 2 lt}{true} ifelse {
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(JPEG needs PostScript Level 2!\n) print flush stop
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} if
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/JPEGdict 20 dict def
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JPEGdict begin
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/NoParamMarkers [ % JPEG markers without additional parameters
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16#D0 16#D1 16#D2 16#D3 16#D4 16#D5 16#D6 16#D7 16#D8 16#01
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] def
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/NotSupportedMarkers [ % JPEG markers not supported by PostScript level 2
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16#C3 16#C5 16#C6 16#C7 16#C8 16#C9 16#CA 16#CB 16#CD 16#CE 16#CF
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] def
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% Names of color spaces
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/ColorSpaceNames << /1 /DeviceGray /3 /DeviceRGB /4 /DeviceCMYK >> def
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% read one byte from file F
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% - ==> int --or-- stop context
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/NextByte {
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F read not { (Read error in ViewJPEG!\n) print flush stop } if
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} bind def
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/SkipSegment { % read two bytes and skip that much data
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NextByte 8 bitshift NextByte add 2 sub { NextByte pop } repeat
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} bind def
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% read width, height, and # of components from JPEG markers
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% and store in dict
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/readJPEGmarkers { % - ==> dict --or-- stop context
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5 dict begin
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{ % loop: read JPEG marker segments until we find SOFn marker or EOF
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NextByte
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16#FF eq { % found marker
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/markertype NextByte def
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% Is it S0F0=baseline, SOF1=extended sequential, SOF2=progressive ?
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markertype dup 16#C0 ge exch 16#C2 le and {
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NextByte pop NextByte pop % segment length
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% Ghostscript and Adobe PS accept only data precision 8
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NextByte 8 ne {
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(Error: not 8 bits per component!\n) print flush stop
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} if
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% Read crucial image parameters
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/height NextByte 8 bitshift NextByte add def
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/width NextByte 8 bitshift NextByte add def
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/colors NextByte def
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VJPGDEBUG { currentdict { exch == == } forall flush } if
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exit
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} if
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% detect several segment types which are not compatible with PS
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NotSupportedMarkers {
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markertype eq {
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(Marker ) print markertype ==
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(not supported!\n) print flush stop
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} if
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} forall
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% Skip segment if marker has parameters associated with it
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true NoParamMarkers { markertype eq {pop false exit} if } forall
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{ SkipSegment } if
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} if
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} loop
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currentdict dup /markertype undef
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end
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} bind def
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end % JPEGdict
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% read image parameters from JPEG file and display the image
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/viewJPEG { % <file|string> ==> -
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save
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JPEGdict begin
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/saved exch def
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/scratch 1 string def
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dup type /stringtype eq { (r) file } if
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/F exch def
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readJPEGmarkers begin
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F 0 setfileposition % reset file pointer
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% We use the whole clipping area for the image (at least in one dimension)
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gsave clippath pathbbox grestore
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/ury exch def /urx exch def
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/lly exch def /llx exch def
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llx lly translate
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width height scale
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% use whole width or height, whichever is appropriate
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urx llx sub width div ury lly sub height div
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2 copy gt { exch } if pop % min
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dup scale
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ColorSpaceNames colors scratch cvs get setcolorspace
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% prepare image dictionary
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<< /ImageType 1
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/Width width
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/Height height
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/ImageMatrix [ width 0 0 height neg 0 height ]
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/BitsPerComponent 8
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% If 4-component (CMYK), assume data is inverted per Adobe Photoshop
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colors 4 eq {
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/Decode [ colors { 1 0 } repeat ]
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} {
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/Decode [ colors { 0 1 } repeat ]
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} ifelse
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/DataSource F /DCTDecode filter
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>> image
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end % image parameter dictionary
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saved end restore
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} bind def
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