Cycles image texture node always premultiplies alpha #55259

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opened 2018-05-30 17:24:40 +02:00 by omgold · 2 comments

When using an image texture node with alpha channel enabled, the color output seems to return always values premultiplied with the alpha value, despite the manual saying this:

RGB color from image. If the image has alpha, the color is premultiplied with alpha if the Alpha output is used, and unpremultiplied or straight if the Alpha output is not used.

It seem to make a difference, whether the alpha socket is connected (the values change somehow), but alpha connected or not, I won't get out the image RGB color values without alpha messing with it.

When using an image texture node with alpha channel enabled, the color output seems to return always values premultiplied with the alpha value, despite the manual saying this: > RGB color from image. If the image has alpha, the color is premultiplied with alpha if the Alpha output is used, and unpremultiplied or straight if the Alpha output is not used. It seem to make a difference, whether the alpha socket is connected (the values change somehow), but alpha connected or not, I won't get out the image RGB color values without alpha messing with it.
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Added subscriber: @omgold

Added subscriber: @omgold

Closed as duplicate of #53672

Closed as duplicate of #53672
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Reference: blender/blender#55259
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