'\" t
.\"     Title: djxl
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 01/29/2023
.\"    Manual: \ \&
.\"    Source: \ \&
.\"  Language: English
.\"
.TH "DJXL" "1" "01/29/2023" "\ \&" "\ \&"
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.SH "NAME"
djxl \- decompress JPEG XL images
.SH "SYNOPSIS"
.sp
\fBdjxl\fR [\fIoptions\fR\&...] \fIinput\&.jxl\fR [\fIoutput\fR]
.SH "DESCRIPTION"
.sp
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 "\fIoutput\fR\-\fBframenumber\fR\&.ext"\&.
.SH "OPTIONS"
.PP
\-V, \-\-version
.RS 4
Print version number and exit
.RE
.PP
\-\-num_reps=\fIN\fR
.RS 4
Sets the number of times to decompress the image\&. Used for benchmarking, the default is 1\&.
.RE
.PP
\-\-num_threads=\fIN\fR
.RS 4
Sets the number of threads to use\&. The default 0 value means the machine default\&.
.RE
.PP
\-\-bits_per_sample=\fIN\fR
.RS 4
Sets the output bit depth\&. The default 0 value means the original (input) bit depth\&.
.RE
.PP
\-\-display_nits=\fI0\&.3\-250\fR
.RS 4
If set to a non\-zero value, tone maps the image the given peak display luminance\&.
.RE
.PP
\-\-color_space=\fIRGB_D65_SRG_Rel_Lin\fR
.RS 4
Defaults to original (input) color space
.RE
.PP
\-s \fIN\fR, \-\-downsampling=\fIN\fR
.RS 4
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\&.
.RE
.PP
\-\-allow_partial_files
.RS 4
Allow decoding of truncated files\&.
.RE
.PP
\-j, \-\-pixels_to_jpeg
.RS 4
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\&.
.RE
.PP
\-q \fIN\fR, \-\-jpeg_quality=\fIN\fR
.RS 4
Sets the JPEG output quality, default is 95\&. Setting an output quality implies \-\-pixels_to_jpeg\&.
.RE
.sp
\-\-norender_spotcolors Disables rendering spot colors\&.
.PP
\-\-preview_out=\fIFILENAME\fR
.RS 4
If specified, writes the preview image to this file\&.
.RE
.PP
\-\-icc_out=\fIFILENAME\fR
.RS 4
If specified, writes the ICC profile of the decoded image to this file\&.
.RE
.PP
\-\-orig_icc_out=\fIFILENAME\fR
.RS 4
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\&.
.RE
.PP
\-\-metadata_out=\fIFILENAME\fR
.RS 4
If specified, writes decoded metadata info to this file in JSON format\&. Used by the conformance test script
.RE
.PP
\-\-print_read_bytes
.RS 4
Print total number of decoded bytes\&.
.RE
.PP
\-\-quiet
.RS 4
Silence output (except for errors)\&.
.RE
.PP
\-h, \-\-help
.RS 4
Displays the options that
djxl
supports\&.
.RE
.SH "EXAMPLES"
.sp
.if n \{\
.RS 4
.\}
.nf
# Decompress a JPEG XL file to PNG
$ djxl input\&.jxl output\&.png

# Reconstruct a losslessly\-recompressed JPEG file
$ djxl lossless\-jpeg\&.jxl reconstructed\&.jpeg
.fi
.if n \{\
.RE
.\}
.sp
# Lossless compression
.sp
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\(cqs lossless):
.sp
.if n \{\
.RS 4
.\}
.nf
# 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)
.fi
.if n \{\
.RE
.\}
.SH "SEE ALSO"
.sp
\fBcjxl\fR(1)