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jamieowen / glsl-blend

glsl photoshop blending modes. glslify formatted.
MIT License
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Saturate whites for color dodge #4

Open mysteryDate opened 6 years ago

mysteryDate commented 6 years ago

According to https://en.wikipedia.org/wiki/Blend_modes#Dodge_and_burn

Blending any color with white gives white. Blending with black does not change the image. The operation is not invertible due to possible clipping of highlights.

As was written, with an equality, blending with values > 1 produces strange results:

Base: screen shot 2018-02-28 at 09 54 37

Blend: screen shot 2018-02-28 at 09 54 45 Which is a procedurally generated sun that has many r and g values > 1.

Result (with opacity = 0.5): screen shot 2018-02-28 at 09 54 14

Replacing the conditional in line 2 with: blend>=1.0: screen shot 2018-02-28 at 09 55 25

Which is kinda cool, but still probably not what is wanted, as the color should saturate at white and opacity = 0.5 here means that at most a 50% grey should be added from the blended image. Finally with line 2 reading (blend>1.0)?1.0:... : screen shot 2018-02-28 at 09 55 34

Which is how I believe the blending would work in photo editing software.

mysteryDate commented 6 years ago

There are possibly other blend modes in this repo that don't account for values > 1, I can fix those two if you'd like. That is, if you agree that values > 1 should be handled.