magick.py: prevent floyd_steinberg() from modifying its input

This commit is contained in:
Johannes 'josch' Schauer 2020-06-03 00:15:55 +02:00
parent 93f65a49c9
commit 802dd4b1f3
Signed by untrusted user: josch
GPG key ID: F2CBA5C78FBD83E1
2 changed files with 18 additions and 17 deletions

View file

@ -17,20 +17,21 @@ def find_closest_palette_color(color, palette):
def floyd_steinberg(img, palette): def floyd_steinberg(img, palette):
for y in range(img.shape[0]): result = numpy.array(img, copy=True)
for x in range(img.shape[1]): for y in range(result.shape[0]):
oldpixel = img[y, x] for x in range(result.shape[1]):
oldpixel = result[y, x]
newpixel = find_closest_palette_color(oldpixel, palette) newpixel = find_closest_palette_color(oldpixel, palette)
quant_error = oldpixel - newpixel quant_error = oldpixel - newpixel
img[y, x] = newpixel result[y, x] = newpixel
if x + 1 < img.shape[1]: if x + 1 < result.shape[1]:
img[y, x + 1] += quant_error * 7 / 16 result[y, x + 1] += quant_error * 7 / 16
if y + 1 < img.shape[0]: if y + 1 < result.shape[0]:
img[y + 1, x - 1] += quant_error * 3 / 16 result[y + 1, x - 1] += quant_error * 3 / 16
img[y + 1, x] += quant_error * 5 / 16 result[y + 1, x] += quant_error * 5 / 16
if x + 1 < img.shape[1] and y + 1 < img.shape[0]: if x + 1 < result.shape[1] and y + 1 < result.shape[0]:
img[y + 1, x + 1] += quant_error * 1 / 16 result[y + 1, x + 1] += quant_error * 1 / 16
return img return result
def convolve_rgba(img, kernel): def convolve_rgba(img, kernel):

10
test.sh
View file

@ -114,16 +114,16 @@ fi
cat << END | ( cd "$tempdir"; md5sum --check $status_arg - ) cat << END | ( cd "$tempdir"; md5sum --check $status_arg - )
cc611e80cde3b9b7adb7723801a4e5d4 alpha.png cc611e80cde3b9b7adb7723801a4e5d4 alpha.png
706175887af8ca1a33cfd93449f970df gray16.png 706175887af8ca1a33cfd93449f970df gray16.png
198e3333d7dc6158f94d1007e75c5bd3 gray1.png ff4d9f18de39be879926be2e65990167 gray1.png
795ff9c5c59cdc95f5a0b9191a7247d9 gray2.png d51900476658a1c9dd26a7b27db8a21f gray2.png
722223ba74be9cba1af4a549076b70d3 gray4.png 722223ba74be9cba1af4a549076b70d3 gray4.png
2320216faa5a10bf0f5f04ebce07f8e1 gray8.png 2320216faa5a10bf0f5f04ebce07f8e1 gray8.png
35a47d6ae6de8c9d0b31aa0cda8648f3 inverse.png 35a47d6ae6de8c9d0b31aa0cda8648f3 inverse.png
6ad810399058a87d8145d8d9a7734da5 normal16.png 6ad810399058a87d8145d8d9a7734da5 normal16.png
c8d2e1f116f31ecdeae050524efca7b6 normal.png c8d2e1f116f31ecdeae050524efca7b6 normal.png
c69edd665ee3546d9eb57fe10cd8095a palette1.png 18a3dfca369f976996ef93389ddfad61 palette1.png
504ecab83662aa2394042a62b1d2eafb palette2.png d38646afa6fa0714be9badef25ff9392 palette2.png
90d1bbe7b26e210d8846cf8692a98b72 palette4.png e1c59e68a68fca3273b6dc164d526ed7 palette4.png
50bf09eb3571901f0bf642b9a733038c palette8.png 50bf09eb3571901f0bf642b9a733038c palette8.png
END END