Fix a couple of minor bugs with build/sanitize-png-files.sh

build/sanitize-png-files.sh

 #!/bin/bash
 # Copyright (c) 2010 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # The optimization code is based on pngslim (http://goo.gl/a0XHg)
 # and executes a similar pipleline to optimize the png file size.
 # The steps that require pngoptimizercl/pngrewrite/deflopt are omitted,
 # but this runs all other processes, including:
 # 1) various color-dependent optimizations using optipng.
@@ skipping 356 matching lines @@
       OPTIMIZE_LEVEL=$OPTARG
       [ "$1" == "-o" ] && shift
       shift;;
     [h?])
       show_help;;
   esac
 done
 
 # Make sure we have all necessary commands installed.
 install_if_not_installed pngcrush
-if [ $OPTIMIZE_LEVEL != 2 ]; then
+if [ $OPTIMIZE_LEVEL == 2 ]; then
   install_if_not_installed optipng
 
   install_if_not_installed advancecomp
   fail_if_not_installed advdef "http://advancemame.sourceforge.net/comp-download.html"
 
   fail_if_not_installed pngout "http://www.jonof.id.au/kenutils"
 fi
 
 # Create tmp directory for crushed png file.
 TMP_DIR=$(mktemp -d)
 
 # Make sure we cleanup temp dir
 trap "rm -rf $TMP_DIR" EXIT
 
 # If no directories are specified, sanitize all directories.
 DIRS=$@
 set ${DIRS:=$ALL_DIRS}
 
 echo "Optimize level=$OPTIMIZE_LEVEL"
 for d in $DIRS; do
   echo "Sanitizing png files in $d"
   sanitize_dir $d
   echo
 done
 
 # Print the results.
-let diff=$TOTAL_OLD_BYTES-$TOTAL_NEW_BYTES
-let percent=$diff*100/$TOTAL_OLD_BYTES
-echo "Processed $PROCESSED_FILE files (out of $TOTAL_FILE files)" \
-     "in $(date -u -d @$SECONDS +%T)s"
-echo "Result : $TOTAL_OLD_BYTES => $TOTAL_NEW_BYTES bytes" \
-     "($diff bytes : $percent %)"
-
+if [ $PROCESSED_FILE == 0 ]; then
+  echo "Did not find any files (out of $TOTAL_FILE files)" \
+       "that could be optimized" \
+       "in $(date -u -d @$SECONDS +%T)s"
+else
+  let diff=$TOTAL_OLD_BYTES-$TOTAL_NEW_BYTES
+  let percent=$diff*100/$TOTAL_OLD_BYTES
+  echo "Processed $PROCESSED_FILE files (out of $TOTAL_FILE files)" \
+       "in $(date -u -d @$SECONDS +%T)s"
+  echo "Result : $TOTAL_OLD_BYTES => $TOTAL_NEW_BYTES bytes" \
+       "($diff bytes : $percent %)"
+fi