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fix blend color #72

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fix blend color #72

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JonaNorman
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The color of your left video is (A, A, A,1.0), and the color of your right video is (R * A, G A, B * A,1.0).
The mix colors in shader are (R
A, G *A, B *A,A).
So shader color is actually pre-multiplied.

And then use it in the VideoRenderer
GLES20.glBlendFunc(GLES20.GL_SRC_ALPHA,GLES20.GL_ONE_MINUS_SRC_ALPHA)
Merged (0,0,0,0)
In fact, the final color is (R A A, G AA, B * A *A, A * A).
This is wrong, blend two pre-multiplied colors that must be used
GLES20.glBlendFunc(GLES20. GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA).

if left video is (A, A, A,1.0), and right video is (R , G , B ,1.0),in shader must Multiplied A

blend premult color must use
 GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA
@erpapa
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erpapa commented Mar 15, 2022

刚开源那会就发现这个问题了,以为没多久就会修复,glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA) alpha多乘了一次,会导致边缘部分色彩偏暗。

@JonaNorman JonaNorman closed this Nov 22, 2022
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