Consider transparency when pasting text on an RGBA image#4566
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This was referenced Apr 23, 2021
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Resolves #4557
When drawing text on an RGBA image, Pillow blends each channel separately between the text and the image. This means that blending white text
(255, 255, 255, 255)with a transparent black background(0, 0, 0, 0)can result in translucent grey, conceivably(127, 127, 127, 127)for example.So instead, if filling L mask onto an RGBA image, weight each of the RGB values by the A value, so that none of
(0, 0, 0, 0)is used because of it's zero alpha.The difference can be seen in the 'New test' row below. Before, there was a black outline to the white text, and now, after. the the white text is hard to see on a transparent image against a white GitHub page.
This does change an existing test result for L mask on RGBA images. However, visually inspecting the images being compared shows no change.