[Impeller] Support alpha in Gradients, fix uneven stops. #36100
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| for (auto i = 1u; i < texture_size - 1; i++) { | ||
| auto scaled_i = i / texture_size; | ||
| auto scaled_i = i / (texture_size * 1.0); |
| // or very small stops. | ||
| AppendColor(next_color, &color_stop_channels); | ||
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| // We've slightly overshot the previous stop. |
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This isn't the case I though it was. If we've passed the previous stop, then we essentially just treat the current stop as the previous stop and run the same code as above.
bdero
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LGTM! Should we land this for the other color sources too? (Could be done in followup(s))
| gradient_info.tile_mode, | ||
| gradient_info.tile_mode); | ||
| frag_color = vec4(frag_color.xyz * frag_color.a, frag_color.a); | ||
| frag_color = vec4(frag_color.xyz * frag_color.a, frag_color.a) * gradient_info.alpha; |
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I left this comment on the other PR, but this still makes me wonder if IPSampleWithTileMode shouldn't really just be IPSampleWithTileModeAndAlpha so we don't forget to do this somewhere - e.g. if and when we implement two point conical gradients.
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Binding non-premultiplied images is the uncommon case -- all layer textures and UI images are premultiplied.
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One idea for making this a bit more semantic is to add an IPPremultiply utility to the shader library and wrap the sampling function in it when we need to premultiply something. This way new contributors who don't know why we're doing the funky alpha multiplies can get a bit more context when first encountering it.
We happen to already have IPUnpremultiply because the advanced blends need to happen with unpremultiplied colors.
All shader functions get flattened by ImpellerC, so utilities like this are free.
Gives all gradients/color source contents an alpha. Additionall corrects some implementation in errors when lerping gradients
Opacity:
Fixes Stops:
Fixes flutter/flutter#111313