NAME

       djxl - decompress JPEG XL images

SYNOPSIS

       djxl [options...] input.jxl [output]

DESCRIPTION

       djxl decompresses a JPEG XL image or animation. The output format is determined by the
       extension of the output file, which can be .png, .jpg, .ppm, .pfm. If the JPEG XL input
       file contains an animation, multiple output files will be produced, with names of the form
       "output-framenumber.ext".

OPTIONS

       -V, --version
           Print version number and exit

       --num_reps=N
           Sets the number of times to decompress the image. Used for benchmarking, the default
           is 1.

       --num_threads=N
           Sets the number of threads to use. The default 0 value means the machine default.

       --bits_per_sample=N
           Sets the output bit depth. The default 0 value means the original (input) bit depth.

       --display_nits=0.3-250
           If set to a non-zero value, tone maps the image the given peak display luminance.

       --color_space=RGB_D65_SRG_Rel_Lin
           Defaults to original (input) color space

       -s N, --downsampling=N
           If set and the input JXL stream is progressive and contains hints for target
           downsampling ratios, the decoder will skip any progressive passes that are not needed
           to produce a partially decoded image intended for this downsampling ratio.

       --allow_partial_files
           Allow decoding of truncated files.

       -j, --pixels_to_jpeg
           By default, if the input JPEG XL contains a recompressed JPEG file, djxl reconstructs
           the exact original JPEG file. This flag causes the decoder to instead decode the image
           to pixels and encode a new (lossy) JPEG. The output file if provided must be a .jpg or
           .jpeg file.

       -q N, --jpeg_quality=N
           Sets the JPEG output quality, default is 95. Setting an output quality implies
           --pixels_to_jpeg.

       --norender_spotcolors Disables rendering spot colors.

       --preview_out=FILENAME
           If specified, writes the preview image to this file.

       --icc_out=FILENAME
           If specified, writes the ICC profile of the decoded image to this file.

       --orig_icc_out=FILENAME
           If specified, writes the ICC profile of the original image to this file. This can be
           different from the ICC profile of the decoded image if --color_space was specified, or
           if the image was XYB encoded and the color conversion to the original profile was not
           supported by the decoder.

       --metadata_out=FILENAME
           If specified, writes decoded metadata info to this file in JSON format. Used by the
           conformance test script

       --print_read_bytes
           Print total number of decoded bytes.

       --quiet
           Silence output (except for errors).

       -h, --help
           Displays the options that djxl supports.

EXAMPLES

           # Decompress a JPEG XL file to PNG
           $ djxl input.jxl output.png

           # Reconstruct a losslessly-recompressed JPEG file
           $ djxl lossless-jpeg.jxl reconstructed.jpeg

       # Lossless compression

       Lossless pixel compression only preserves the pixels losslessly, not the input bitstream.
       To check that the pixels are identical, one can do something like the following (if this
       says 0, then the maximum pixel error is 0, so it’s lossless):

           # Lossless compression of PNG:
           $ cjxl -d 0.0 input.png lossless.png

           # Decompress a JPEG XL file to PNG
           $ djxl lossless.jxl lossless.png

           $ compare -metric pae input.png lossless.png null:
           0 (0)

SEE ALSO

       cjxl(1)

                                            03/14/2023                                    DJXL(1)