[BUG] SKBlendMode.Multiply not working correctly

[martinrhan]

Description

The multiply blend mode in computer graphics should convert each part of RGBA to float ranging at [0,1], and multiply them. That means if one of the color is 0, then the outcome should be zero no matter what the another one is. However, when I multiply color 0 and color 0xFF000000 (by the way, the uint representation of color takes first byte as alpha, this is inconsistent with the convention). the outcome is not zero.

Code

Draw the following paint

var shader = SKShader.CreateCompose(SKShader.CreateColor(0), SKShader.CreateColor(new(0,0,0,255)), SKBlendMode.Multiply);
var paint =  new SKPaint() { Shader = shader };

Expected Behavior

The paint should draw nothing, as the composed color is 0 after multiplication.

Actual Behavior

It draws zero RGB with 255 alpha.

Version of SkiaSharp

3.x (Alpha)

Last Known Good Version of SkiaSharp

Other (Please indicate in the description)

IDE / Editor

Visual Studio (Windows)

Platform / Operating System

Windows

Platform / Operating System Version

Windows 11 Home 23H2

Devices

Nitro AN515-58

Relevant Screenshots

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Relevant Log Output

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