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Merge pull request #315 from d-schmidt/master
fix Issue #312 + gif optimize improvement
This commit is contained in:
Alex Clark ☺
commit
07f338f194
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@ -54,7 +54,6 @@ class GifImageFile(ImageFile.ImageFile):
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format = "GIF"
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format_description = "Compuserve GIF"
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global_palette = None
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def data(self):
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@ -71,13 +70,9 @@ class GifImageFile(ImageFile.ImageFile):
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raise SyntaxError("not a GIF file")
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self.info["version"] = s[:6]
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self.size = i16(s[6:]), i16(s[8:])
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self.tile = []
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flags = i8(s[10])
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bits = (flags & 7) + 1
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if flags & 128:
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@ -122,7 +117,8 @@ class GifImageFile(ImageFile.ImageFile):
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self.im = self.dispose
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self.dispose = None
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self.palette = self.global_palette
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from copy import copy
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self.palette = copy(self.global_palette)
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while True:
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@ -252,6 +248,9 @@ def _save(im, fp, filename):
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palette = im.encoderinfo["palette"]
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except KeyError:
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palette = None
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if im.palette:
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# use existing if possible
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palette = im.palette.getdata()[1]
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header, usedPaletteColors = getheader(imOut, palette, im.encoderinfo)
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for s in header:
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@ -344,70 +343,68 @@ def getheader(im, palette=None, info=None):
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optimize = info and info.get("optimize", 0)
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# start of header
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# Header Block
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# http://www.matthewflickinger.com/lab/whatsinagif/bits_and_bytes.asp
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header = [
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b"GIF87a" + # magic
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o16(im.size[0]) + # size
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o16(im.size[1])
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b"GIF87a" + # signature + version
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o16(im.size[0]) + # canvas width
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o16(im.size[1]) # canvas height
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]
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# if the user adds a palette, use it
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usedPaletteColors = None
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if im.mode == "P":
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if palette and isinstance(palette, bytes):
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sourcePalette = palette[:768]
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else:
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sourcePalette = im.im.getpalette("RGB")[:768]
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else: # L-mode
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if palette and isinstance(palette, bytes):
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sourcePalette = palette[:768]
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else:
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sourcePalette = bytearray([i//3 for i in range(768)])
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if palette is not None and isinstance(palette, bytes):
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paletteBytes = palette[:768]
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else:
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usedPaletteColors = paletteBytes = None
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if optimize:
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usedPaletteColors = []
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if optimize:
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# minimize color palette if wanted
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# check which colors are used
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i = 0
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for count in im.histogram():
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if count:
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usedPaletteColors.append(i)
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i += 1
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# create the new palette if not every color is used
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if len(usedPaletteColors) < 256:
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paletteBytes = b""
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newPositions = {}
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i = 0
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for count in im.histogram():
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if count:
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usedPaletteColors.append(i)
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# pick only the used colors from the palette
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for oldPosition in usedPaletteColors:
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paletteBytes += sourcePalette[oldPosition*3:oldPosition*3+3]
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newPositions[oldPosition] = i
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i += 1
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countUsedPaletteColors = len(usedPaletteColors)
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# create the global palette
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if im.mode == "P":
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# colour palette
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if countUsedPaletteColors > 0 and countUsedPaletteColors < 256:
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paletteBytes = b"";
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# pick only the used colors from the palette
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for i in usedPaletteColors:
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paletteBytes += im.im.getpalette("RGB")[i*3:i*3+3]
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else :
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paletteBytes = im.im.getpalette("RGB")[:768]
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else:
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# greyscale
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if countUsedPaletteColors > 0 and countUsedPaletteColors < 256:
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paletteBytes = b"";
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# add only the used grayscales to the palette
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for i in usedPaletteColors:
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paletteBytes += o8(i)*3
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else :
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paletteBytes = bytearray([i//3 for i in range(768)])
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# TODO improve this, maybe add numpy support
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# replace the palette color id of all pixel with the new id
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if countUsedPaletteColors > 0 and countUsedPaletteColors < 256:
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# replace the palette color id of all pixel with the new id
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imageBytes = bytearray(im.tobytes())
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for i in range(len(imageBytes)):
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for newI in range(countUsedPaletteColors):
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if imageBytes[i] == usedPaletteColors[newI]:
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imageBytes[i] = newI
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break
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imageBytes[i] = newPositions[imageBytes[i]]
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im.frombytes(bytes(imageBytes))
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if not paletteBytes:
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paletteBytes = sourcePalette
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# Logical Screen Descriptor
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# calculate the palette size for the header
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import math
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colorTableSize = int(math.ceil(math.log(len(paletteBytes)//3, 2)))-1
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if colorTableSize < 0: colorTableSize = 0
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header.append(o8(colorTableSize + 128)) # size of global color table + global color table flag
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header.append(o8(0) + o8(0)) # background + reserved/aspect
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# end of screen descriptor header
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# size of global color table + global color table flag
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header.append(o8(colorTableSize + 128))
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# background + reserved/aspect
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header.append(o8(0) + o8(0))
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# end of Logical Screen Descriptor
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# add the missing amount of bytes
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# the palette has to be 2<<n in size
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@ -415,7 +412,7 @@ def getheader(im, palette=None, info=None):
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if actualTargetSizeDiff > 0:
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paletteBytes += o8(0) * 3 * actualTargetSizeDiff
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# global color palette
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# Header + Logical Screen Descriptor + Global Color Table
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header.append(paletteBytes)
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return header, usedPaletteColors
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@ -499,26 +499,24 @@ def _save(im, fp, filename, chunk=putchunk, check=0):
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#
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# attempt to minimize storage requirements for palette images
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if "bits" in im.encoderinfo:
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# number of bits specified by user
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n = 1 << im.encoderinfo["bits"]
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colors = 1 << im.encoderinfo["bits"]
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else:
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# check palette contents
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n = 256 # FIXME
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if im.palette:
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colors = len(im.palette.getdata()[1])//3
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else:
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colors = 256
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if n <= 2:
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if colors <= 2:
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bits = 1
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elif n <= 4:
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elif colors <= 4:
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bits = 2
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elif n <= 16:
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elif colors <= 16:
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bits = 4
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else:
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bits = 8
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if bits != 8:
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mode = "%s;%d" % (mode, bits)
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@ -555,8 +553,11 @@ def _save(im, fp, filename, chunk=putchunk, check=0):
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b'\0') # 12: interlace flag
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if im.mode == "P":
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palette_bytes = (2 ** bits) * 3
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chunk(fp, b"PLTE", im.im.getpalette("RGB")[:palette_bytes])
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palette_byte_number = (2 ** bits) * 3
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palette_bytes = im.im.getpalette("RGB")[:palette_byte_number]
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while len(palette_bytes) < palette_byte_number:
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palette_bytes += b'\0'
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chunk(fp, b"PLTE", palette_bytes)
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if "transparency" in im.encoderinfo:
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if im.mode == "P":
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