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amigajpegv4.lha
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djpeg.man
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1993-01-10
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DDDDJJJJPPPPEEEEGGGG((((1111)))) DDDDJJJJPPPPEEEEGGGG((((1111))))
2222 AAAAuuuugggguuuusssstttt 1111999999992222
NNNNAAAAMMMMEEEE
djpeg - decompress a JPEG file to an image file
SSSSYYYYNNNNOOOOPPPPSSSSIIIISSSS
ddddjjjjppppeeeegggg [ ----ccccoooolllloooorrrrssss _N ] [ ----ggggiiiiffff ] [ ----ppppnnnnmmmm ] [ ----rrrrlllleeee ] [ ----ttttaaaarrrrggggaaaa ] [
----bbbblllloooocccckkkkssssmmmmooooooootttthhhh ] [ ----ggggrrrraaaayyyyssssccccaaaalllleeee ] [ ----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy _N ] [ ----nnnnooooddddiiiitttthhhheeeerrrr ] [ ----oooonnnneeeeppppaaaassssssss
] [ ----vvvveeeerrrrbbbboooosssseeee ] [ ----ddddeeeebbbbuuuugggg ] [ _f_i_l_e_n_a_m_e ]
DDDDEEEESSSSCCCCRRRRIIIIPPPPTTTTIIIIOOOONNNN
ddddjjjjppppeeeegggg decompresses the named JPEG file, or the standard input if no
file is named, and produces an image file on the standard output.
PBMPLUS (PPM/PGM), GIF, Targa, or RLE (Utah Raster Toolkit) output
format can be selected. (RLE is supported only if the URT library is
available.)
OOOOPPPPTTTTIIIIOOOONNNNSSSS
All switch names may be abbreviated; for example, ----ggggrrrraaaayyyyssssccccaaaalllleeee may be
written ----ggggrrrraaaayyyy or ----ggggrrrr. Most of the "basic" switches can be abbreviated
to as little as one letter. Upper and lower case are equivalent (thus
----GGGGIIIIFFFF is the same as ----ggggiiiiffff). British spellings are also accepted (e.g.,
----ggggrrrreeeeyyyyssssccccaaaalllleeee), though for brevity these are not mentioned below.
The basic switches are:
----ccccoooolllloooorrrrssss _N
Reduce image to at most N colors. This reduces the number of
colors used in the output image, so that it can be displayed on a
colormapped display or stored in a colormapped file format. For
example, if you have an 8-bit display, you'd need to reduce to
256 or fewer colors.
----qqqquuuuaaaannnnttttiiiizzzzeeee _N
Same as ----ccccoooolllloooorrrrssss. ----ccccoooolllloooorrrrssss is the recommended name, ----qqqquuuuaaaannnnttttiiiizzzzeeee is
provided only for backwards compatibility.
----ggggiiiiffff Select GIF output format. Since GIF does not support more than
256 colors, ----ccccoooolllloooorrrrssss 222255556666 is assumed (unless you specify a smaller
number of colors).
----ppppnnnnmmmm Select PBMPLUS (PPM/PGM) output format (this is the default
format). PGM is emitted if the JPEG file is gray-scale or if
----ggggrrrraaaayyyyssssccccaaaalllleeee is specified; otherwise PPM is emitted.
----rrrrlllleeee Select RLE output format. (Requires URT library.)
----ttttaaaarrrrggggaaaa
Select Targa output format. Gray-scale format is emitted if the
JPEG file is gray-scale or if ----ggggrrrraaaayyyyssssccccaaaalllleeee is specified; otherwise,
colormapped format is emitted if ----ccccoooolllloooorrrrssss is specified; otherwise,
24-bit full-color format is emitted.
- 1 - Formatted: January 10, 1993
DDDDJJJJPPPPEEEEGGGG((((1111)))) DDDDJJJJPPPPEEEEGGGG((((1111))))
2222 AAAAuuuugggguuuusssstttt 1111999999992222
Switches for advanced users:
----bbbblllloooocccckkkkssssmmmmooooooootttthhhh
Perform cross-block smoothing. This is quite memory-intensive
and only seems to improve the image at very low quality settings
(----qqqquuuuaaaalllliiiittttyyyy 10 to 20 or so). At normal quality settings it may
make the image worse.
----ggggrrrraaaayyyyssssccccaaaalllleeee
Force gray-scale output even if JPEG file is color. Useful for
viewing on monochrome displays.
----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy _N
Set limit for amount of memory to use in processing large images.
Value is in thousands of bytes, or millions of bytes if "M" is
attached to the number. For example, ----mmmmaaaaxxxx 4444mmmm selects 4000000
bytes. If more space is needed, temporary files will be used.
----nnnnooooddddiiiitttthhhheeeerrrr
Do not use dithering in color quantization. By default, Floyd-
Steinberg dithering is applied when quantizing colors, but on
some images dithering may result in objectionable "graininess".
If that happens, you can turn off dithering with ----nnnnooooddddiiiitttthhhheeeerrrr.
----nnnnooooddddiiiitttthhhheeeerrrr is ignored unless you also say ----ccccoooolllloooorrrrssss _N.
----oooonnnneeeeppppaaaassssssss
Use one-pass instead of two-pass color quantization. The one-
pass method is faster and needs less memory, but it produces a
lower-quality image. ----oooonnnneeeeppppaaaassssssss is ignored unless you also say
----ccccoooolllloooorrrrssss _N. Also, the one-pass method is always used for gray-
scale output (the two-pass method is no improvement then).
----vvvveeeerrrrbbbboooosssseeee
Enable debug printout. More ----vvvv's give more output. Also,
version information is printed at startup.
----ddddeeeebbbbuuuugggg
Same as ----vvvveeeerrrrbbbboooosssseeee.
EEEEXXXXAAAAMMMMPPPPLLLLEEEESSSS
This example decompresses the JPEG file foo.jpg, automatically
quantizes to 256 colors, and saves the output in GIF format in
foo.gif:
ddddjjjjppppeeeegggg ----ggggiiiiffff _f_o_o._j_p_g >>>> _f_o_o._g_i_f
EEEENNNNVVVVIIIIRRRROOOONNNNMMMMEEEENNNNTTTT
JJJJPPPPEEEEGGGGMMMMEEEEMMMM
If this environment variable is set, its value is the default
memory limit. The value is specified as described for the
----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy switch. JJJJPPPPEEEEGGGGMMMMEEEEMMMM overrides the default value specified
- 2 - Formatted: January 10, 1993
DDDDJJJJPPPPEEEEGGGG((((1111)))) DDDDJJJJPPPPEEEEGGGG((((1111))))
2222 AAAAuuuugggguuuusssstttt 1111999999992222
when the program was compiled, and itself is overridden by an
explicit ----mmmmaaaaxxxxmmmmeeeemmmmoooorrrryyyy.
SSSSEEEEEEEE AAAALLLLSSSSOOOO
ccccjjjjppppeeeegggg(1)
ppppppppmmmm(5), ppppggggmmmm(5)
Wallace, Gregory K. "The JPEG Still Picture Compression Standard",
Communications of the ACM, April 1991 (vol. 34, no. 4), pp. 30-44.
AAAAUUUUTTTTHHHHOOOORRRR
Independent JPEG Group
BBBBUUUUGGGGSSSS
Arithmetic coding is not supported for legal reasons.
Still not as fast as we'd like.
- 3 - Formatted: January 10, 1993