Gamma issue when display linear color

Question

fsjack OP

Created Feb ’24

Replies 1

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Participants 2

Hi, I'm displaying linear gray by CAMetalLayer with the shader below.

fragment float4 fragmentShader(VertexOut in [[stage_in]],
                               texture2d<float, access::sample> BGRATexture [[ texture(0) ]])
{
    float color = in.texCoordinates.x;
    return float4(float3(color), 1.0);
}

And my CAMetalLayer has been set to linearSRGB.

metalLayer.colorspace = CGColorSpace(name: CGColorSpace.linearSRGB)
metalLayer.pixelFormat = .bgra8Unorm

Why the display seem add gamma? Apparently the middle gray is 187 but not 128.

WX20240207-124528@2x.png

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Answer 1

Alecazam OP

Mar ’24

You are sending an srgb format and specifiying a linear colorspace. bgra8unorm means the data is typically stored gamma space. bgra8unorm_srgb converts to linear on reads and would match your color space.

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