ImagePalette: loading a translucent RGBA color into an RGB palette will break the palette #6652

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1. radarhere

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   Palette

   on Oct 9, 2022
2. radarhere commented on Oct 9, 2022

   

   radarhere

   on Oct 9, 2022

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   For context, the code to handle opaque RGBA colors was added in #5552.

   I think that raising a ValueError is the better solution. If Pillow just accepted the input, this could surprise the user later when they discover that the RGBA color isn't really there.
3. jsbueno

   added a commit that references this issue on Oct 9, 2022

   Fix python-pillow#6652: Handle translucent color used in RGB ImagePal…

   ...

   This issue will close once commit f9a3178 is merged into the 'main' branch.

   f9a3178
4. jsbueno commented on Oct 9, 2022

   

   jsbueno

   on Oct 9, 2022

   Last edited by jsbueno

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   Oh, -
   i did the ValueError thing - but it looks like event he code in texts expect to be able to insert translucent colors,
   and get the alpha rounded.

   Tests/test_image_access.py::TestCffi::test_p_putpixel_rgb_rgba[P] FAILED [ 31%]
   
   =================================== FAILURES ===================================
   _____________________ TestCffi.test_p_putpixel_rgb_rgba[P] _____________________
   
   self = <Tests.test_image_access.TestCffi object at 0x00007fb00ce8b8a0>
   mode = 'P'
   
       @pytest.mark.parametrize("mode", ("P", "PA"))
       def test_p_putpixel_rgb_rgba(self, mode):
           for color in [(255, 0, 0), (255, 0, 0, 127)]:
               im = Image.new(mode, (1, 1))
               access = PyAccess.new(im, False)
   >           access.putpixel((0, 0), color)
   
   Tests/test_image_access.py:351: 
   (...)
   E                       ValueError: RGB ImagePalette can't handle non-opaque RGBA colors
   

   So - do we use the RGB components?
   Or should the failing tests be changed?
5. radarhere commented on Oct 10, 2022

   

   radarhere

   on Oct 10, 2022

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   The error you're hitting is when the tests try to set an RGBA value for a P image. The test was changed to use a translucent value in #6504, which was a PR about allowing RGB and RGBA values for PA images. Setting a translucent value for a P image was a side-effect, not the intention. So I'm happy to change the test.

   I've created jsbueno#2
6. radarhere

   closed this as completedin #6654on Oct 10, 2022