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libobs: Add DrawNonlinearAlpha technique

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This allows OBS to mimic other programs that incorrectly use alpha.

Requires premultiplied blend state.
This commit is contained in:
jpark37 2021-04-23 23:01:35 -07:00
parent 59603f47ad
commit 840e2b3d43
1 changed files with 38 additions and 0 deletions
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38
libobs/data/default.effect
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@ -33,6 +33,35 @@ float4 PSDrawAlphaDivide(VertInOut vert_in) : TARGET
return float4(rgba.rgb * multiplier, alpha);
}
float srgb_linear_to_nonlinear_channel(float u)
{
return (u <= 0.0031308) ? (12.92 * u) : ((1.055 * pow(u, 1.0 / 2.4)) - 0.055);
}
float3 srgb_linear_to_nonlinear(float3 v)
{
return float3(srgb_linear_to_nonlinear_channel(v.r), srgb_linear_to_nonlinear_channel(v.g), srgb_linear_to_nonlinear_channel(v.b));
}
float srgb_nonlinear_to_linear_channel(float u)
{
return (u <= 0.04045) ? (u / 12.92) : pow((u + 0.055) / 1.055, 2.4);
}
float3 srgb_nonlinear_to_linear(float3 v)
{
return float3(srgb_nonlinear_to_linear_channel(v.r), srgb_nonlinear_to_linear_channel(v.g), srgb_nonlinear_to_linear_channel(v.b));
}
float4 PSDrawNonlinearAlpha(VertInOut vert_in) : TARGET
{
float4 rgba = image.Sample(def_sampler, vert_in.uv);
rgba.rgb = srgb_linear_to_nonlinear(rgba.rgb);
rgba.rgb *= rgba.a;
rgba.rgb = srgb_nonlinear_to_linear(rgba.rgb);
return rgba;
}
technique Draw
{
pass
@ -50,3 +79,12 @@ technique DrawAlphaDivide
pixel_shader = PSDrawAlphaDivide(vert_in);
}
}
technique DrawNonlinearAlpha
{
pass
{
vertex_shader = VSDefault(vert_in);
pixel_shader = PSDrawNonlinearAlpha(vert_in);
}
}