1186129 - WebGL texture conversions: Fix assignment of alpha in pack premultiply of RA16F

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect)

Description

[Kyle Fung]

Current implementation of pack premultiply for RA16F from WebGLTexelConversions.h :

> template<> MOZ_ALWAYS_INLINE void
> pack<WebGLTexelFormat::RA16F, WebGLTexelPremultiplicationOp::Premultiply, uint16_t, uint16_t>(const uint16_t* __restrict src, uint16_t* __restrict dst)
> {
>     float scaleFactor = unpackFromFloat16(src[3]);
>     dst[0] = packToFloat16(unpackFromFloat16(src[0]) * scaleFactor);
>     dst[1] = scaleFactor;
> }

The assignment of dst[1] should be to src[3] not scaleFactor since scaleFactor is a float unpacked from src[3].

Comment 1

[Kyle Fung]

Attachment: fix-alpha-assignment.patch

Comment 2

[Kelsey Gilbert [:jgilbert]]

Comment on attachment 8636723 [details] [diff] [review]
fix-alpha-assignment.patch

Review of attachment 8636723 [details] [diff] [review]:
-----------------------------------------------------------------

::: dom/canvas/WebGLTexelConversions.h
@@ +859,5 @@
>  pack<WebGLTexelFormat::RA32F, WebGLTexelPremultiplicationOp::Premultiply, float, float>(const float* __restrict src, float* __restrict dst)
>  {
>      float scaleFactor = src[3];
>      dst[0] = src[0] * scaleFactor;
> +    dst[1] = src[3];

This is clearer, but it's the same result.

Comment 3

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/730b6090f696

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/730b6090f696