/usr/share/ghostscript/lib
Edit: /usr/share/ghostscript/lib/viewgif.ps (5395B)
% Copyright (C) 2001-2021 Artifex Software, Inc.
% All Rights Reserved.
%
% 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.
%
% Refer to licensing information at http://www.artifex.com or contact
% Artifex Software, Inc., 1305 Grant Avenue - Suite 200, Novato,
% CA 94945, U.S.A., +1(415)492-9861, for further information.
%
% viewgif.ps
% Display a GIF file.
/read1 %
read1
{ read pop
} bind def
/read2 % read2
{ dup read1 exch read1 8 bitshift add
} bind def
/readGIFheader % readGIFheader
{ 20 dict begin
dup 6 string readstring pop
dup (GIF87a) eq exch (GIF89a) eq or not
{ (Not a GIF file.\n) print cleartomark stop
} if
dup read2 /Width exch def
dup read2 /Height exch def
dup read1
dup 128 ge /GlobalColor exch def
dup -4 bitshift 7 and 1 add /BitsPerPixel exch def %***BOGUS?***
dup 8 and 0 ne /PaletteSorted exch def
7 and 1 add dup /BitsPerPixel exch def
1 exch bitshift /PaletteSize exch def
dup read1 /BackgroundIndex exch def
dup read1 15 add 64 div /AspectRatio exch def
GlobalColor
{ PaletteSize 3 mul string readstring pop
/GlobalPalette exch def
} if
currentdict end
} bind def
/readGIFimageHeader % readGIFimageHeader
% Note: GIF header must be on dict stack
{ 10 dict begin
{ dup read1
dup (!) 0 get ne { exit } if pop % extension
dup read1 pop
{ dup read1 dup 0 eq { pop exit } if { dup read1 pop } repeat
} loop
} loop
(,) 0 get ne
{ (Not a GIF image.\n) print stop
} if
dup read2 /Left exch def
dup read2 /Top exch def
dup read2 /Width exch def
dup read2 /Height exch def
dup read1
dup 128 ge /LocalColor exch def
dup 64 and 0 ne /Interlaced exch def
LocalColor
{ 7 and 1 add /BitsPerPixel exch def
1 BitsPerPixel bitshift 3 mul string readstring pop
/Palette exch def
}
{ pop pop /Palette GlobalPalette def
}
ifelse
currentdict end
} bind def
/imageGIF % imageGIF
{ /ImageOut where
{ pop
% We know BitsPerComponent = 8, Decode = [0 255].
% and there is only a single data source which is
% either a filter or a string whose size is exactly
% the width of the row.
dup /DataSource get dup type /stringtype eq
{ ImageOut exch writestring
}
{ pop dup /Width get string
1 index /Height get
{ 1 index /DataSource get 1 index readstring pop
ImageOut exch writestring
}
repeat pop pop
}
ifelse
}
{ image
}
ifelse
} bind def
/viewGIF % viewGIF -
{ save 20 dict begin
/saved exch def
dup type /stringtype eq { (r) file } if
/F exch def
/ImageOutFile where { /ImageOut ImageOutFile (w) file def } if
F readGIFheader /Header exch def
currentdict Header end begin begin
VGIFDEBUG { Header { exch == == } forall (----------------\n) print flush } if
F readGIFimageHeader /ImageHeader exch def
currentdict ImageHeader end begin begin
VGIFDEBUG { ImageHeader { exch == == } forall (----------------\n) print flush } if
/D F
<< /InitialCodeLength F read1
/FirstBitLowOrder true
/BlockData true
/EarlyChange 0
>> /LZWDecode filter def
[/Indexed /DeviceRGB 1 BitsPerPixel bitshift 1 sub Palette] setcolorspace
matrix currentmatrix
0 1 3 { 2 copy get dup 0 ne { dup abs div } if 3 copy put pop pop } for
setmatrix
<< /ImageType 1
/ImageMatrix [1 0 0 -1 0 Height]
/BitsPerComponent 8
/Decode [0 255]
Interlaced
{ /Width Width /Height 1
/row Width string def
/DataSource row
>> /I exch def
/inter % inter -
{ /denom exch def /num exch def
gsave
/lines Height denom 1 sub add num sub denom idiv def
0 1 lines 1 sub {
Height exch denom mul num add sub
I /ImageMatrix get 5 3 -1 roll put
D row readstring pop pop
I imageGIF
} for
grestore
}
bind def
0 8 inter
4 8 inter
2 4 inter
1 2 inter
}
{ /Width Width /Height Height
/DataSource D
>> imageGIF
}
ifelse
saved end end end restore
} bind def
% This lets you do stuff on the command line like:
% gs -sDEVICE=pdfwrite -o stuff%03d.pdf viewgif.ps -c "(image.gif) << /PageSize 2 index viewGIFgetsize 2 array astore >> setpagedevice viewGIF"
% so the output size is influenced by the original image.
/viewGIFgetsize % ==> [width height]
{
save 20 dict begin
/saved exch def
dup type /stringtype eq { (r) file } if
/F exch def
F readGIFheader /Header exch def
currentdict Header end begin begin
VGIFDEBUG { Header { exch == == } forall (----------------\n) print flush } if
F readGIFimageHeader /ImageHeader exch def
currentdict ImageHeader end begin begin
F 0 setfileposition % reset file pointer
Width Height
saved end end end restore
} bind def