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#!/bin/sh
#
# Bisects JPEG XL encoding quality parameter to reach a given
# target bits-per-pixel value.
# (To be used directly, or as a template for tailored processing.)
#
# Usage: cjxl_bisect_size {input_filename} {output_filename} {target_bpp}
#
# We take the `bisector` tool from $PATH, or, if not available,
# try to locate it in the same directory as the current script.
# The `get_bpp` helper is taken from the same directory as the current script.
#
input_filename=$1
output_filename=$2
target_size=$3
script_dir=$(dirname $(readlink -f $0))
bisect_tool=$(which bisector)
if [ -z $bisect_tool ] ; then
bisect_tool="${script_dir}/bisector"
fi
jxl_get_bpp_helper="${script_dir}/jxl_get_bpp_helper"
# If $CJXL_BIN is set, we use this instead of looking for `cjxl` on $PATH.
cjxl_bin=${CJXL_BIN}
if [ -z $cjxl_bin ] ; then
cjxl_bin="cjxl"
fi
# Using `identify` from ImageMagick here.
num_pixels=$(identify -format "%w*%h\n" /tmp/baseball.png|bc)
# Allow 0.5% tolerance in size (--rtol=0.005).
exec $bisect_tool --var=BISECT --range=0.01,15.0 --target=$target_size \
--rtol_val=0.005 \
--cmd="$cjxl_bin --distance=\$BISECT ${input_filename} ${output_filename}_bisect_\$BISECT.jxl ; (find ${output_filename}_bisect_\$BISECT.jxl -printf \"scale=10;%s/$num_pixels\n\" | bc -l)" \
--final="mv ${output_filename}_bisect_\$BISECT.jxl ${output_filename}; rm -f ${output_filename}_bisect_*.jxl" \
--verbosity=1
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