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Fix greyscale computation and inverted coords #8905

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merged 4 commits into from
Jul 29, 2023
Merged

Fix greyscale computation and inverted coords #8905

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af92097
Fix greyscale computation and inverted coords
Jul 29, 2023
5718c2b
Fix test
Jul 29, 2023
9e53e23
Add test cases
Jul 29, 2023
e5dfb18
Add reference to the greyscaling formula
Jul 29, 2023
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12 changes: 8 additions & 4 deletions digital_image_processing/dithering/burkes.py
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Original file line number Diff line number Diff line change
Expand Up @@ -39,20 +39,24 @@ def __init__(self, input_img, threshold: int):
def get_greyscale(cls, blue: int, green: int, red: int) -> float:
"""
>>> Burkes.get_greyscale(3, 4, 5)
3.753
4.185
>>> Burkes.get_greyscale(0, 0, 0)
0.0
>>> Burkes.get_greyscale(255, 255, 255)
255.0
"""
return 0.114 * blue + 0.587 * green + 0.2126 * red
return 0.114 * blue + 0.587 * green + 0.299 * red
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@tianyizheng02 tianyizheng02 Jul 29, 2023 •
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according to Internet, it's either (0.2126R + 0.7152G + 0.0722B) or (0.299R + 0.587G + 0.114B)

Could you add a source for these numbers so that we can avoid mistakes like this in the future?

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Good idea, done :)


def process(self) -> None:
for y in range(self.height):
for x in range(self.width):
greyscale = int(self.get_greyscale(*self.input_img[y][x]))
if self.threshold > greyscale + self.error_table[y][x]:
self.output_img[y][x] = (0, 0, 0)
current_error = greyscale + self.error_table[x][y]
current_error = greyscale + self.error_table[y][x]
else:
self.output_img[y][x] = (255, 255, 255)
current_error = greyscale + self.error_table[x][y] - 255
current_error = greyscale + self.error_table[y][x] - 255
"""
Burkes error propagation (`*` is current pixel):

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