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Allow remapping P images with RGBA palettes #6350

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merged 1 commit into from Jun 10, 2022
Merged

Allow remapping P images with RGBA palettes #6350

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9 changes: 9 additions & 0 deletions Tests/test_image.py
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Expand Up @@ -604,6 +604,15 @@ def test_remap_palette(self):
with Image.open("Tests/images/hopper.gif") as im:
assert_image_equal(im, im.remap_palette(list(range(256))))

# Test identity transform with an RGBA palette
im = Image.new("P", (256, 1))
for x in range(256):
im.putpixel((x, 0), x)
im.putpalette(list(range(256)) * 4, "RGBA")
im_remapped = im.remap_palette(list(range(256)))
assert_image_equal(im, im_remapped)
assert im.palette.palette == im_remapped.palette.palette

# Test illegal image mode
with hopper() as im:
with pytest.raises(ValueError):
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27 changes: 19 additions & 8 deletions src/PIL/Image.py
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Expand Up @@ -1867,10 +1867,15 @@ def remap_palette(self, dest_map, source_palette=None):
if self.mode not in ("L", "P"):
raise ValueError("illegal image mode")

bands = 3
palette_mode = "RGB"
if source_palette is None:
if self.mode == "P":
self.load()
source_palette = self.im.getpalette("RGB")[:768]
palette_mode = self.im.getpalettemode()
if palette_mode == "RGBA":
bands = 4
source_palette = self.im.getpalette(palette_mode, palette_mode)
else: # L-mode
source_palette = bytearray(i // 3 for i in range(768))

Expand All @@ -1879,7 +1884,9 @@ def remap_palette(self, dest_map, source_palette=None):

# pick only the used colors from the palette
for i, oldPosition in enumerate(dest_map):
palette_bytes += source_palette[oldPosition * 3 : oldPosition * 3 + 3]
palette_bytes += source_palette[
oldPosition * bands : oldPosition * bands + bands
]
new_positions[oldPosition] = i

# replace the palette color id of all pixel with the new id
Expand All @@ -1905,19 +1912,23 @@ def remap_palette(self, dest_map, source_palette=None):
m_im = self.copy()
m_im.mode = "P"

m_im.palette = ImagePalette.ImagePalette("RGB", palette=mapping_palette * 3)
m_im.palette = ImagePalette.ImagePalette(
palette_mode, palette=mapping_palette * bands
)
# possibly set palette dirty, then
# m_im.putpalette(mapping_palette, 'L') # converts to 'P'
# or just force it.
# UNDONE -- this is part of the general issue with palettes
m_im.im.putpalette("RGB;L", m_im.palette.tobytes())
m_im.im.putpalette(palette_mode + ";L", m_im.palette.tobytes())

m_im = m_im.convert("L")

# Internally, we require 768 bytes for a palette.
new_palette_bytes = palette_bytes + (768 - len(palette_bytes)) * b"\x00"
m_im.putpalette(new_palette_bytes)
m_im.palette = ImagePalette.ImagePalette("RGB", palette=palette_bytes)
# Internally, we require 256 palette entries.
new_palette_bytes = (
palette_bytes + ((256 * bands) - len(palette_bytes)) * b"\x00"
)
m_im.putpalette(new_palette_bytes, palette_mode)
m_im.palette = ImagePalette.ImagePalette(palette_mode, palette=palette_bytes)

if "transparency" in self.info:
try:
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