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adjust the transparency index after successful optimize

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skip transparency block if transparent color is not used after optimize
This commit is contained in:
David Schmidt 2013-05-24 13:12:40 +02:00
parent 71b30352d9
commit b66d888b0e
1 changed files with 30 additions and 13 deletions
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31
PIL/GifImagePlugin.py
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@ -253,7 +253,8 @@ def _save(im, fp, filename):
except KeyError: except KeyError:
palette = None palette = None
for s in getheader(imOut, palette, im.encoderinfo): header, usedPaletteColors = getheader(imOut, palette, im.encoderinfo)
for s in header:
fp.write(s) fp.write(s)
flags = 0 flags = 0
@ -275,13 +276,27 @@ def _save(im, fp, filename):
except KeyError: except KeyError:
pass pass
else: else:
transparency = int(transparency)
# optimize the block away if transparent color is not used
transparentColorExists = True
# adjust the transparency index after optimize
if usedPaletteColors is not None and len(usedPaletteColors) < 256:
for i in range(len(usedPaletteColors)):
if usedPaletteColors[i] == transparency:
transparency = i
transparentColorExists = True
break
else:
transparentColorExists = False
# transparency extension block # transparency extension block
if transparentColorExists:
fp.write(b"!" + fp.write(b"!" +
o8(249) + # extension intro o8(249) + # extension intro
o8(4) + # length o8(4) + # length
o8(1) + # transparency info present o8(1) + # transparency info present
o16(0) + # duration o16(0) + # duration
o8(int(transparency)) # transparency index o8(transparency) # transparency index
+ o8(0)) + o8(0))
# local image header # local image header
@ -330,13 +345,15 @@ def getheader(im, palette=None, info=None):
optimize = info and info.get("optimize", 0) optimize = info and info.get("optimize", 0)
# start of header # start of header
s = [ header = [
b"GIF87a" + # magic b"GIF87a" + # magic
o16(im.size[0]) + # size o16(im.size[0]) + # size
o16(im.size[1]) o16(im.size[1])
] ]
# if the user adds a palette, use it # if the user adds a palette, use it
usedPaletteColors = None
if palette is not None and isinstance(palette, bytes): if palette is not None and isinstance(palette, bytes):
paletteBytes = palette[:768] paletteBytes = palette[:768]
else: else:
@ -388,8 +405,8 @@ def getheader(im, palette=None, info=None):
import math import math
colorTableSize = int(math.ceil(math.log(len(paletteBytes)//3, 2)))-1 colorTableSize = int(math.ceil(math.log(len(paletteBytes)//3, 2)))-1
if colorTableSize < 0: colorTableSize = 0 if colorTableSize < 0: colorTableSize = 0
s.append(o8(colorTableSize + 128)) # size of global color table + global color table flag header.append(o8(colorTableSize + 128)) # size of global color table + global color table flag
s.append(o8(0) + o8(0)) # background + reserved/aspect header.append(o8(0) + o8(0)) # background + reserved/aspect
# end of screen descriptor header # end of screen descriptor header
# add the missing amount of bytes # add the missing amount of bytes
@ -399,8 +416,8 @@ def getheader(im, palette=None, info=None):
paletteBytes += o8(0) * 3 * actualTargetSizeDiff paletteBytes += o8(0) * 3 * actualTargetSizeDiff
# global color palette # global color palette
s.append(paletteBytes) header.append(paletteBytes)
return s return header, usedPaletteColors
def getdata(im, offset = (0, 0), **params): def getdata(im, offset = (0, 0), **params):