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Support negative height in BMP files #18

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Merged
merged 3 commits into from
Aug 6, 2019
Merged

Support negative height in BMP files #18

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34dae3a
Support negative height in BMP files
cogliano Aug 1, 2019
67cff5a
Fixed indendation issue from PyLint
cogliano Aug 2, 2019
238f5ac
Another tab fix
cogliano Aug 2, 2019
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19 changes: 16 additions & 3 deletions adafruit_imageload/bmp/indexed.py
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Original file line number Diff line number Diff line change
Expand Up @@ -59,7 +59,13 @@ def load(file, width, height, data_start, colors, color_depth, *, bitmap=None, p
while colors > 2 ** minimum_color_depth:
minimum_color_depth *= 2

bitmap = bitmap(width, height, colors)
#convert unsigned int to signed int when height is negative
if height > 0x7fffffff:
height = height - 4294967296
theight = height
if theight < 0:
theight = 0 - theight
bitmap = bitmap(width, theight, colors)
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Can you just declare the bitmap as below, and remove lines 65-67?

bitmap = bitmap(width, abs(height), colors)

This would save the (very limited) memory and time spent allocating the object "theight", since it isn't used again.

Edit: I got the line numbers wrong the first time. I tested the PR with and without this change, and both worked.

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Thanks, I should have seen that. I just made a pull request.

file.seek(data_start)
line_size = width // (8 // color_depth)
if width % (8 // color_depth) != 0:
Expand All @@ -69,8 +75,15 @@ def load(file, width, height, data_start, colors, color_depth, *, bitmap=None, p

chunk = bytearray(line_size)
mask = (1 << minimum_color_depth) - 1

for y in range(height - 1, -1, -1):
if height > 0:
range1 = height - 1
range2 = -1
range3 = -1
else:
range1 = 0
range2 = abs(height)
range3 = 1
for y in range(range1, range2, range3):
file.readinto(chunk)
pixels_per_byte = 8 // color_depth
offset = y * width
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