#!/bin/sh # # Usage: # script/lossless_JPEG_compress [-m bbb] file.jpg { file2.jpg ...} # # Losslessly compress in-place the specified JPEG file(s). # Any compression done may be reported as an INFO line on stderr. # The files must be valid writable JPEGs. # # By default no compression is done and the source files are left as-is. # Maximum size to consider potentially targeted to a mobile device. # Below this size try to avoid many-scan progressive as CPU-intensive. # # Size threshold is overridden by -m size. # # A threshold of 0 effectively removes the limit. # # Possibly override this restriction if big (10%?) savings are to be had. # TODO: allow override/removal of this limit from the command-line. MOBSIZEMAX=10240 if [ "-m" = "$1" ]; then MOBSIZEMAX="$2" # Discard the -m bbb args. shift shift fi # Tries various plausible output formats to reduce size, # including progressive, even for small files. # Look at possible alternative scans as in: # https://cloudinary.com/blog/progressive_jpegs_and_green_Martians # Uses jpegtran: gives up immediately if not available. JT=/usr/local/bin/jpegtran if [ ! -x $JT ]; then JT=/usr/bin/jpegtran if [ ! -x $JT ]; then echo "WARNING: jpegtran not available" 1>&2 # Quit immediately leaving files untouched. exit 1 fi fi # Writes to an intermediate file with a temporary suffix. # Some files already have very long names, # so making this suffix too long may make some tasks fail. TMPSUFFIX="U.tmp" # Process the files. for f in $*; do if [ ! -s "$f" ]; then echo "WARNING: missing or zero-length file $f" 1>&2 continue fi TMPFILE=$f.$TMPSUFFIX rm -f $TMPFILE ISIZE="`wc -c < $f`" #echo "INFO: file $ISIZE $f" 1>&2 # Earlier encodings are preferred, # eg fewer passes to save mobile CPU and battery, # or easier for users to know when complete, # or more likely to be compatible with all browsers, # or less likely to produce transient 'green Martians'. # In any case, replace immediately if smaller, # and report against original size. # First conversion with smallest/equal size will win. # Baseline, ie non-progressive. # Most mobile-friendly: least CPU and memory to decode. $JT -copy none -optimize <$f >$TMPFILE NPSIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$NPSIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $NPSIZE (non-progressive) $f" 1>&2 fi # # "Two-pass progressive" scans file. # # DHD20180409: doesn't provide any optimisation on current hero set. # # Just two passes, all DC first, so very steep improvement. # # Should be easier on mobile battery as fewer scans. # SCANSTWO=$0.twopass.scans # if [ ! -s $SCANSTWO ]; then # echo "WARNING: $SCANSTWO scans file not available" 1>&2 # # Can continue, just won't be able to try this scan type. # else # # Suppress "Invalid scan script at entry 1" for grayscale images. # $JT -copy none -optimize -scans $SCANSTWO <$f >$TMPFILE 2>/dev/null # TPSIZE="`wc -c < $TMPFILE`" # if [ -s $TMPFILE -a "$TPSIZE" -lt "`wc -c < $f`" ]; then # mv -f $TMPFILE $f # echo "INFO: file $ISIZE shrunk to $TPSIZE (two-pass progressive) $f" 1>&2 # fi # fi # "Semi-semi-progressive" scans file. # Fewer passes (4) than the "Semi-progressive" scans file. # Should be easier on mobile battery as fewer scans. SCANSSSEMI=$0.semisemiprog.scans if [ ! -s $SCANSSSEMI ]; then echo "WARNING: $SCANSSSEMI scans file not available" 1>&2 # Can continue, just won't be able to try this scan type. else # Suppress "Invalid scan script at entry 1" for grayscale images. $JT -copy none -optimize -scans $SCANSSSEMI <$f >$TMPFILE 2>/dev/null SSSIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$SSSIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $SSSIZE (semi-semi-progressive) $f" 1>&2 fi fi # "Semi-progressive" scans file. # Fewer passes (5) than the default progressive scans file. # Should be easier on mobile battery as fewer scans. SCANSSEMI=$0.semiprog.scans if [ ! -s $SCANSSEMI ]; then echo "WARNING: $SCANSSEMI scans file not available" 1>&2 # Can continue, just won't be able to try this scan type. else # Suppress "Invalid scan script at entry 1" for grayscale images. $JT -copy none -optimize -scans $SCANSSEMI <$f >$TMPFILE 2>/dev/null SESIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$SESIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $SESIZE (semi-progressive) $f" 1>&2 fi fi # # "Steep-progressive" scans file. # # DHD20180408: doesn't provide any optimisation on current hero set. # SCANSSTEEP=$0.steepprog.scans # if [ ! -s $SCANSSTEEP ]; then # echo "WARNING: $SCANSSTEEP scans file not available" 1>&2 # # Can continue, just won't be able to try this scan type. # else # # Suppress "Invalid scan script at entry 1" for grayscale images. # $JT -copy none -optimize -scans $SCANSSTEEP <$f >$TMPFILE 2>/dev/null # STSIZE="`wc -c < $TMPFILE`" # if [ -s $TMPFILE -a "$STSIZE" -lt "`wc -c < $f`" ]; then # mv -f $TMPFILE $f # echo "INFO: file $ISIZE shrunk to $STSIZE (steep-progressive) $f" 1>&2 # fi # fi # "Three-pass progressive" scans file. # Three passes, all luma (0) then all 2 then all 1. # Small number of passes kinder to mobile CPU/battery. # Some risk of green Martians, so try late. SCANSTHREE=$0.threepass.scans if [ ! -s $SCANSTHREE ]; then echo "WARNING: $SCANSTHREE scans file not available" 1>&2 # Can continue, just won't be able to try this scan type. else # Suppress "Invalid scan script at entry 1" for grayscale images. $JT -copy none -optimize -scans $SCANSTHREE <$f >$TMPFILE 2>/dev/null TPSIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$TPSIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $TPSIZE (three-pass progressive) $f" 1>&2 fi fi ### BELOW HERE NOT FOR MOBILE (~10k) UNLESS FORCED (OR >10% SAVINGS?) ### Attempt to avoid huge numbers of scans to save mobile battery life. if [ "`wc -c < $f`" -gt "$MOBSIZEMAX" ]; then # Default (ten-pass) progressive. # Lots of extra CPU time for mobiles, so not good. $JT -copy none -optimize -progressive <$f >$TMPFILE PSIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$PSIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $PSIZE (progressive) $f" 1>&2 fi # "Six-pass progressive" scans file. # Six passes, all DC first separately, then all AC afterwards. # Some risk of green Martians, so try late. # Order is 0, 2, 1 for DC then 2, 1, 0 for AC, to try to reduce Martians. SCANSSIX=$0.sixpass.scans if [ ! -s $SCANSSIX ]; then echo "WARNING: $SCANSSIX scans file not available" 1>&2 # Can continue, just won't be able to try this scan type. else # Suppress "Invalid scan script at entry 1" for grayscale images. $JT -copy none -optimize -scans $SCANSSIX <$f >$TMPFILE 2>/dev/null SPSIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$SPSIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $SPSIZE (six-pass progressive) $f" 1>&2 fi fi # "Seven-pass progressive" scans file. # Seven passes, all DC first separately, then AC with extra luma split. # Some risk of green Martians, so try late. SCANSSEVEN=$0.sevenpass.scans if [ ! -s $SCANSSEVEN ]; then echo "WARNING: $SCANSSEVEN scans file not available" 1>&2 # Can continue, just won't be able to try this scan type. else # Suppress "Invalid scan script at entry 1" for grayscale images. $JT -copy none -optimize -scans $SCANSSEVEN <$f >$TMPFILE 2>/dev/null SPSIZE="`wc -c < $TMPFILE`" if [ -s $TMPFILE -a "$SPSIZE" -lt "`wc -c < $f`" ]; then mv -f $TMPFILE $f echo "INFO: file $ISIZE shrunk to $SPSIZE (seven-pass progressive) $f" 1>&2 fi fi fi rm -f $TMPFILE done exit 0