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Refactor out the palette remapping to Image.Image
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wiredfool
Andrew Murray
parent
24285fdc28
commit
1e9afb3ecb
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@ -537,6 +537,16 @@ def _save_netpbm(im, fp, filename):
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_FORCE_OPTIMIZE = False
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def _get_optimize(im, info):
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"""
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Palette optimization is a potentially expensive operation.
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This function determines if the palette should be optimized using
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some heuristics, then returns the list of palette entries in use.
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:param im: Image object
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:param info: encoderinfo
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:returns: list of indexes of palette entries in use, or None
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"""
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if im.mode in ("P", "L") and info and info.get("optimize", 0):
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# Potentially expensive operation.
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@ -579,6 +589,16 @@ def _get_header_palette(palette_bytes):
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return palette_bytes
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def _get_palette_bytes(im, palette, info):
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"""
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Gets the palette for inclusion in the gif header, if optimization is
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requested or required, the palette is rewritten and the image is
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mutatated in place.
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:param im: Image object
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:param palette: bytes object containing the source palette, or ....
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:param info: encoderinfo
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:returns: Bytes, len<=768 suitable for inclusion in gif header
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"""
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if im.mode == "P":
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if palette and isinstance(palette, bytes):
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source_palette = palette[:768]
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@ -594,61 +614,14 @@ def _get_palette_bytes(im, palette, info):
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used_palette_colors = _get_optimize(im, info)
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if used_palette_colors is not None:
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palette_bytes = b""
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new_positions = [0]*256
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# pick only the used colors from the palette
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for i, oldPosition in enumerate(used_palette_colors):
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palette_bytes += source_palette[oldPosition*3:oldPosition*3+3]
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new_positions[oldPosition] = i
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# replace the palette color id of all pixel with the new id
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# Palette images are [0..255], mapped through a 1 or 3
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# byte/color map. We need to remap the whole image
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# from palette 1 to palette 2. New_positions is
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# an array of indexes into palette 1. Palette 2 is
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# palette 1 with any holes removed.
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# We're going to leverage the convert mechanism to use the
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# C code to remap the image from palette 1 to palette 2,
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# by forcing the source image into 'L' mode and adding a
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# mapping 'L' mode palette, then converting back to 'L'
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# sans palette thus converting the image bytes, then
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# assigning the optimized RGB palette.
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# perf reference, 9500x4000 gif, w/~135 colors
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# 14 sec prepatch, 1 sec postpatch with optimization forced.
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mapping_palette = bytearray(new_positions)
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m_im = im.copy()
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m_im.mode = 'P'
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m_im.palette = ImagePalette.ImagePalette("RGB",
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palette=mapping_palette*3,
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size=768)
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#possibly set palette dirty, then
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#m_im.putpalette(mapping_palette, 'L') # converts to 'P'
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# or just force it.
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# UNDONE -- this is part of the general issue with palettes
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m_im.im.putpalette(*m_im.palette.getdata())
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m_im = m_im.convert('L')
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# Internally, we require 768 bytes for a palette.
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new_palette_bytes = (palette_bytes +
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(768 - len(palette_bytes)) * b'\x00')
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m_im.putpalette(new_palette_bytes)
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m_im.palette = ImagePalette.ImagePalette("RGB",
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palette=palette_bytes,
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size=len(palette_bytes))
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m_im = im.remap_palette(used_palette_colors, source_palette)
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palette_bytes = m_im.palette.palette
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# oh gawd, this is modifying the image in place so I can pass by ref.
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# REFACTOR SOONEST
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im.frombytes(m_im.tobytes())
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if not palette_bytes:
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im.im = m_im.im
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im.palette = m_im.palette
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else:
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palette_bytes = source_palette
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# returning palette, _not_ padded to 768 bytes like our internal ones.
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77
PIL/Image.py
77
PIL/Image.py
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@ -1514,6 +1514,83 @@ class Image(object):
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return self.pyaccess.putpixel(xy, value)
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return self.im.putpixel(xy, value)
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def remap_palette(self, dest_map, source_palette=None):
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"""
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Rewrites the image to reorder the palette.
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:param dest_map: A list of indexes into the original palette.
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e.g. [1,0] would swap a two item palette, and list(range(255))
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is the identity transform.
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:param source_palette: Bytes or None.
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:returns: An :py:class:`~PIL.Image.Image` object.
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"""
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from . import ImagePalette
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if self.mode not in ("L", "P"):
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raise ValueError("illegal image mode")
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if source_palette is None:
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if self.mode == "P":
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source_palette = self.im.getpalette("RGB")[:768]
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else: # L-mode
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source_palette = bytearray(i//3 for i in range(768))
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palette_bytes = b""
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new_positions = [0]*256
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# pick only the used colors from the palette
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for i, oldPosition in enumerate(dest_map):
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palette_bytes += source_palette[oldPosition*3:oldPosition*3+3]
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new_positions[oldPosition] = i
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# replace the palette color id of all pixel with the new id
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# Palette images are [0..255], mapped through a 1 or 3
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# byte/color map. We need to remap the whole image
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# from palette 1 to palette 2. New_positions is
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# an array of indexes into palette 1. Palette 2 is
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# palette 1 with any holes removed.
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# We're going to leverage the convert mechanism to use the
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# C code to remap the image from palette 1 to palette 2,
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# by forcing the source image into 'L' mode and adding a
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# mapping 'L' mode palette, then converting back to 'L'
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# sans palette thus converting the image bytes, then
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# assigning the optimized RGB palette.
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# perf reference, 9500x4000 gif, w/~135 colors
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# 14 sec prepatch, 1 sec postpatch with optimization forced.
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mapping_palette = bytearray(new_positions)
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m_im = self.copy()
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m_im.mode = 'P'
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m_im.palette = ImagePalette.ImagePalette("RGB",
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palette=mapping_palette*3,
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size=768)
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#possibly set palette dirty, then
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#m_im.putpalette(mapping_palette, 'L') # converts to 'P'
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# or just force it.
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# UNDONE -- this is part of the general issue with palettes
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m_im.im.putpalette(*m_im.palette.getdata())
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m_im = m_im.convert('L')
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# Internally, we require 768 bytes for a palette.
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new_palette_bytes = (palette_bytes +
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(768 - len(palette_bytes)) * b'\x00')
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m_im.putpalette(new_palette_bytes)
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m_im.palette = ImagePalette.ImagePalette("RGB",
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palette=palette_bytes,
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size=len(palette_bytes))
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return m_im
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def resize(self, size, resample=NEAREST):
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"""
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Returns a resized copy of this image.
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