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Add preserve_tone option to autocontrast

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This commit is contained in:
elejke 2021-03-21 21:15:13 +03:00
parent ddcc936643
commit c585e6ab6b
2 changed files with 8 additions and 2 deletions
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1
Tests/test_imageops.py
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@ -29,6 +29,7 @@ def test_sanity():
ImageOps.autocontrast(hopper("L"), cutoff=(2, 10))
ImageOps.autocontrast(hopper("L"), ignore=[0, 255])
ImageOps.autocontrast(hopper("L"), mask=hopper("L"))
ImageOps.autocontrast(hopper("L"), preserve_tone=True)
ImageOps.colorize(hopper("L"), (0, 0, 0), (255, 255, 255))
ImageOps.colorize(hopper("L"), "black", "white")

9
src/PIL/ImageOps.py
View File

@ -61,7 +61,7 @@ def _lut(image, lut):
# actions
def autocontrast(image, cutoff=0, ignore=None, mask=None):
def autocontrast(image, cutoff=0, ignore=None, mask=None, preserve_tone=False):
"""
Maximize (normalize) image contrast. This function calculates a
histogram of the input image (or mask region), removes ``cutoff`` percent of the
@ -77,9 +77,14 @@ def autocontrast(image, cutoff=0, ignore=None, mask=None):
:param mask: Histogram used in contrast operation is computed using pixels
within the mask. If no mask is given the entire image is used
for histogram computation.
:param preserve_tone: Preserve image tone in Photoshop-like style autocontrast.
:return: An image.
"""
histogram = image.histogram(mask)
if preserve_tone:
histogram = image.convert("L").histogram(mask)
else:
histogram = image.histogram(mask)
lut = []
for layer in range(0, len(histogram), 256):
h = histogram[layer : layer + 256]