DJPEG

NAME

SYNOPSIS

DESCRIPTION

djpeg decompresses the named JPEG file, or the standard input if no file is named, and produces an image file on the standard output. PPM, GIF, Targa, or RLE output format can be selected. (RLE is supported only if the URT library is available.)  

OPTIONS

-G

Select GIF output format (implies -q, with default of 256 colors).

-P

Select PPM or PGM output format (this is the default). PGM is emitted if the JPEG file is gray-scale or if -g is specified.

-R

Select RLE output format. Requires URT library.

-T

Select Targa output format. Gray-scale format is emitted if the JPEG file is gray-scale or if -g is specified; otherwise, colormapped format is emitted if -q is specified; otherwise, 24-bit full-color format is emitted.

-g

Force gray-scale output even if input is color.

-q N

Quantize to N colors. This reduces the number of colors 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 quantize to 256 or fewer colors.

-D

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 -D. -D is ignored unless you also say -q or -G.

-1

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. -1 is ignored unless you also say -q or -G. Also, the one-pass method is always used for gray-scale output (the two-pass method is no improvement then).

-b

Perform cross-block smoothing. This is quite memory-intensive and only seems to improve the image at low quality settings (-Q 10 to 20 or so). At normal -Q settings it may make the image worse.

-d

Enable debug printout. More -d's give more output. Also, version information is printed at startup.

-m memory

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, -m 4m selects 4000000 bytes. If more space is needed, temporary files will be used.

EXAMPLES

This example decompresses the JPEG file foo.jpg, quantizes to 256 colors, and saves the output in GIF format in foo.gif:

djpeg -G foo.jpg > foo.gif

SEE ALSO

AUTHOR

BUGS

Not as fast as we'd like.

Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXAMPLES

SEE ALSO

AUTHOR

BUGS