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Add option to set dither param on quantize

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Default the option to `1`, as per original setting
This commit is contained in:
Katie McLaughlin 2019-03-09 10:36:13 +11:00
parent 22ae782320
commit 0b63579f39
3 changed files with 27 additions and 2 deletions
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16
Tests/test_image_quantize.py
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@ -46,3 +46,19 @@ class TestImageQuantize(PillowTestCase):
converted = image.quantize()
self.assert_image(converted, 'P', converted.size)
self.assert_image_similar(converted.convert('RGB'), image, 1)
def test_quantize_no_dither(self):
image = hopper()
palette = Image.open('Tests/images/caption_6_33_22.png').convert('P')
converted = image.quantize(dither=0, palette=palette)
self.assert_image(converted, 'P', converted.size)
def test_quantize_dither_diff(self):
image = hopper()
palette = Image.open('Tests/images/caption_6_33_22.png').convert('P')
dither = image.quantize(dither=1, palette=palette)
nodither = image.quantize(dither=0, palette=palette)
self.assertNotEqual(dither.tobytes(), nodither.tobytes())

5
docs/releasenotes/6.0.0.rst
View File

@ -107,6 +107,11 @@ DIB File Format
Pillow now supports reading and writing the DIB "Device Independent Bitmap" file format.
Image.quantize
^^^^^^^^^^^^^^
The `dither` option is now a customisable parameter (was previously hardcoded to `1`). This parameter takes the same values used in `Image.convert`
Other Changes
=============

8
src/PIL/Image.py
View File

@ -1049,7 +1049,7 @@ class Image(object):
new_im.info['transparency'] = trns
return new_im
def quantize(self, colors=256, method=None, kmeans=0, palette=None):
def quantize(self, colors=256, method=None, kmeans=0, palette=None, dither=1):
"""
Convert the image to 'P' mode with the specified number
of colors.
@ -1062,6 +1062,10 @@ class Image(object):
:param kmeans: Integer
:param palette: Quantize to the palette of given
:py:class:`PIL.Image.Image`.
:param dither: Dithering method, used when converting from
mode "RGB" to "P" or from "RGB" or "L" to "1".
Available methods are NONE or FLOYDSTEINBERG (default).
Default: 1 (legacy setting)
:returns: A new image
"""
@ -1089,7 +1093,7 @@ class Image(object):
raise ValueError(
"only RGB or L mode images can be quantized to a palette"
)
im = self.im.convert("P", 1, palette.im)
im = self.im.convert("P", dither, palette.im)
return self._new(im)
return self._new(self.im.quantize(colors, method, kmeans))