newbitmaps: Speed up image conversion by using PIL.

Running ImageMagick + PIL is a redundant task; we should let PIL
do flatten, resize, and exporting to different format.

Before: real 11m54s, user 37m10s.
After: real 8m3s, user 16m33s.

BRANCH=none
BUG=none
TEST=make

Change-Id: I65f1e5b769161650310abca46851824755402d9b
Reviewed-on: https://gerrit.chromium.org/gerrit/37200
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Commit-Ready: Hung-Te Lin <hungte@chromium.org>

scripts/newbitmaps/images/build_images

@@ -14,54 +14,23 @@ BACKGROUND_IMAGE=Background_white.png
 # Output file name.
 BMPBLK_OUTPUT="bmpblock.bin"
 
+SCRIPT_BASE="$(dirname $(readlink -f "$0"))"
+
 die() {
   echo "ERROR: $*" >&2
   exit 1
 }
 
 convert_to_bmp3() {
-  local input="$1"
-  local folder="$2"
-  local param="$3"
-  local output="$(basename "$input")"
+  local folder="$1"
+  local param="$2"
+  shift
+  shift
 
-  # Always output as .bmp
-  output="${output%.*}.bmp"
-  mkdir -p "$folder"
+  # convert_to_bmp3.py takes '--scale' while ImageMagic takes '-scale'.
+  [ -n "$param" ] && param="-$param"
 
-  # TODO(hungte) Use PIL to replace ImageMagic.
-
-  # When input has Alpha channel, we need to fill the background properly
-  # otherwise ImageMagick will fill it with black.  The operation (-flatten) is
-  # so slow so we only want to do that if the input source really has
-  # transparency.
-  if [ "$#" -gt 3 ]; then
-    flatten="$4"
-  else
-    # Auto-detect
-    if [ "$(identify -format "%A" "$input")" = "True" ]; then
-      flatten="-background $BACKGROUND_COLOR -flatten"
-    else
-      flatten=""
-    fi
-  fi
-
-  echo "$input -> $folder/$output $flatten"
-  convert "$input" $flatten \
-    -compress none -alpha off -colors 256 \
-    $param "BMP3:$folder/$output"
-
-  # ImageMagic quantization may choose arbitrary color depth, even if we assign
-  # -depth or -colors; so a single-color background may become 1 bit per pixel
-  # after convertion. To workaround that, we use Python Image Library which
-  # always generates 8bpp BMP file.
-  # TODO(hungte) Find a better way to decide if PIL is required. Unfortunately,
-  # ImageMagic identify "%z" is not always what we're looking for...
-  local fn="$folder/$output"
-  # Converting from '1' to 'P' may be not supported by PIL, so converting to
-  # 'RGB' mode first is required.
-  local param="convert('RGB').convert('P', dither=None, palette=Image.ADAPTIVE)"
-  python -c "import Image;Image.open('$fn').$param.save('$fn')"
+  $SCRIPT_BASE/convert_to_bmp3.py $param --outdir "$folder" "$@"
 }
 
 main() {
@@ -163,9 +132,9 @@ main() {
   # Url.bmp by <span foreground="blue">http://</span>.
   for X in *.png assets/*.png; do
     if [ "$X" = "$BACKGROUND_IMAGE" ]; then
-      convert_to_bmp3 "$X" "$output" "$background_scale_param"
+      convert_to_bmp3 "$output" "$background_scale_param" "$X"
     else
-      convert_to_bmp3 "$X" "$output" "$scale_param"
+      convert_to_bmp3 "$output" "$scale_param" "$X"
     fi
   done
 
@@ -174,9 +143,7 @@ main() {
   # speed up.
   echo "Preparing common strings..."
   base="../strings"
-  for X in $base/*.png; do
-    convert_to_bmp3 "$X" "$output" "$scale_param" ""
-  done
+  convert_to_bmp3 "$output" "$scale_param" $base/*.png
 
   echo "Preparing localized messages... $LOCALES"
   base="../strings/localized_text"
@@ -191,9 +158,7 @@ main() {
   fi
   for locale in $LOCALES; do
     # Prepare all locales.
-    for X in $base/$locale/*.png; do
-      convert_to_bmp3 "$X" "$output/locale/$locale" "$scale_param" ""
-    done
+    convert_to_bmp3 "$output/locale/$locale" "$scale_param" $base/$locale/*.png
   done
 
   if [ -n "$replace_files" ]; then
@@ -210,9 +175,7 @@ main() {
 
   echo "Preparing fonts..."
   base="../strings/font"
-  for X in $base/*.png; do
-    convert_to_bmp3 "$X" "$output/font" "$scale_param" ""
-  done
+  convert_to_bmp3 "$output/font" "$scale_param" $base/*.png
   bmpblk_font --outfile "$output/hwid_fonts.bin" "$output"/font/*.bmp
 
   # Create YAML file.

scripts/newbitmaps/images/convert_to_bmp3.py

@@ -0,0 +1,85 @@
+#!/usr/bin/env python
+# Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import getopt
+import os
+import re
+import sys
+
+import Image
+
+
+BACKGROUND_COLOR = (255, 255, 255)
+DEFAULT_OUTPUT_EXT = '.bmp'
+
+
+def parse_scale_factor(pattern, original_size):
+  # Format: w%xh%, or wxh!
+  factor = re.findall(r'^([0-9]+)%x([0-9]+)%$', pattern)
+  if factor:
+    w, h = factor[0]
+    return (int(int(w) / 100.0 * original_size[0]),
+            int(int(h) / 100.0 * original_size[1]))
+
+  factor = re.findall(r'^([0-9]+)x([0-9]+)!?$', pattern)
+  if factor:
+    return map(int, factor[0])
+
+  raise Exception('Unknown scaling parameter: %s', pattern)
+
+
+def convert_to_bmp(input_file, scale, outdir, background=BACKGROUND_COLOR):
+  source = Image.open(input_file)
+  output_file = os.path.join(
+      outdir,
+      os.path.basename(input_file).rpartition('.')[0] + DEFAULT_OUTPUT_EXT)
+
+  # Process alpha channel and transparency.
+  if source.mode == 'RGBA':
+    target = Image.new('RGB', source.size, background)
+    source.load()  # required for source.split()
+    mask = source.split()[-1]
+    target.paste(source, mask=mask)
+  elif (source.mode == 'P') and ('transparency' in source.info):
+    exit('Sorry, PNG with RGBA palette is not supported.')
+  elif source.mode != 'RGB':
+    target = source.convert('RGB')
+  else:
+    target = source
+
+  # Process scaling
+  if scale:
+    new_size = parse_scale_factor(scale, source.size)
+    target = target.resize(new_size, Image.BICUBIC)
+
+  # Export and downsample color space.
+  target.convert('P', dither=None, palette=Image.ADAPTIVE).save(output_file)
+
+
+def main(argv):
+  scale_param = ''
+  outdir = ''
+  try:
+    opts, args = getopt.getopt(argv[1:], '', ('scale=', 'outdir='))
+    for key, value in opts:
+      if key == '--scale':
+        scale_param = value
+      elif key == '--outdir':
+        outdir = value
+    if len(args) < 1:
+      raise Exception('need more param')
+  except:
+    exit('Usage: ' + argv[0] +
+         ' [--scale WxH!|--scale W%xH%] [--outdir DIR] files(s)...')
+
+  if outdir and not os.path.isdir(outdir):
+    os.makedirs(outdir)
+
+  for source_file in args:
+    convert_to_bmp(source_file, scale_param, outdir)
+
+
+if __name__ == '__main__':
+  main(sys.argv)