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Added Transparency mask unpacker for BMP files

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This commit is contained in:
wiredfool 2016-04-06 07:38:24 -07:00
parent e84e02997c
commit 0e3caec317
2 changed files with 30 additions and 3 deletions
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17
PIL/BmpImagePlugin.py
View File

@ -112,7 +112,8 @@ class BmpImageFile(ImageFile.ImageFile):
# 40 byte headers only have the three components in the bitfields masks,
# ref: https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376(v=vs.85).aspx
# See also https://github.com/python-pillow/Pillow/issues/1293
file_info['a_mask'] = 0xff000000
# Note below, None is a key in the SUPPORTED and MASK_MODES structures.
file_info['a_mask'] = None
for mask in ['r_mask', 'g_mask', 'b_mask']:
file_info[mask] = i32(read(4))
file_info['rgb_mask'] = (file_info['r_mask'], file_info['g_mask'], file_info['b_mask'])
@ -134,12 +135,22 @@ class BmpImageFile(ImageFile.ImageFile):
# ----------------- Process BMP with Bitfields compression (not palette)
if file_info['compression'] == self.BITFIELDS:
SUPPORTED = {
32: [(0xff0000, 0xff00, 0xff, 0x0), (0xff0000, 0xff00, 0xff, 0xff000000), (0x0, 0x0, 0x0, 0x0)],
32: [(0xff0000, 0xff00, 0xff, 0x0),
(0xff0000, 0xff00, 0xff, None),
(0xff0000, 0xff00, 0xff, 0xff000000),
(0x0, 0x0, 0x0, 0x0)],
24: [(0xff0000, 0xff00, 0xff)],
16: [(0xf800, 0x7e0, 0x1f), (0x7c00, 0x3e0, 0x1f)]
}
# From inspecting DIB files from Vista screenshots, the
# file format is a 32 bit color image, where the 'Alpha'
# channel for screenshots is actually a transparency mask
# (255-alpha) where 00 is solid and ff is transparent. I
# can't find documentation of this, but it matches
# imagemagick's conversion of the .dib file into a .png.
MASK_MODES = {
(32, (0xff0000, 0xff00, 0xff, 0x0)): "BGRX",
(32, (0xff0000, 0xff00, 0xff, None)): "BGRT",
(32, (0xff0000, 0xff00, 0xff, 0xff000000)): "BGRA",
(32, (0x0, 0x0, 0x0, 0x0)): "BGRA",
(24, (0xff0000, 0xff00, 0xff)): "BGR",
@ -149,7 +160,7 @@ class BmpImageFile(ImageFile.ImageFile):
if file_info['bits'] in SUPPORTED:
if file_info['bits'] == 32 and file_info['rgba_mask'] in SUPPORTED[file_info['bits']]:
raw_mode = MASK_MODES[(file_info['bits'], file_info['rgba_mask'])]
self.mode = "RGBA" if raw_mode in ("BGRA",) else self.mode
self.mode = "RGBA" if raw_mode in ("BGRA", "BGRT") else self.mode
elif file_info['bits'] in (24, 16) and file_info['rgb_mask'] in SUPPORTED[file_info['bits']]:
raw_mode = MASK_MODES[(file_info['bits'], file_info['rgb_mask'])]
else:

16
libImaging/Unpack.c
View File

@ -738,6 +738,21 @@ unpackBGRA(UINT8* out, const UINT8* in, int pixels)
}
}
static void
unpackBGRT(UINT8* out, const UINT8* in, int pixels)
{
int i;
/* RGBA, reversed bytes */
/* Transparency map, rather than an alpha channel */
for (i = 0; i < pixels; i++) {
out[R] = in[2];
out[G] = in[1];
out[B] = in[0];
out[A] = 255 - in[3];
out += 4; in += 4;
}
}
/* Unpack to "CMYK" image */
@ -1111,6 +1126,7 @@ static struct {
{"RGBA", "RGBA;4B", 16, ImagingUnpackRGBA4B},
{"RGBA", "RGBA;16B", 64, unpackRGBA16B},
{"RGBA", "BGRA", 32, unpackBGRA},
{"RGBA", "BGRT", 32, unpackBGRT},
{"RGBA", "ARGB", 32, unpackARGB},
{"RGBA", "ABGR", 32, unpackABGR},
{"RGBA", "YCCA;P", 32, ImagingUnpackYCCA},