obs-studio/libobs/data/bilinear_lowres_scale.effect

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/*
* bilinear low res scaling, samples 8 pixels of a larger image to scale to a
* low resolution image below half size
*/
uniform float4x4 ViewProj;
uniform texture2d image;
sampler_state textureSampler {
Filter = Linear;
AddressU = Clamp;
AddressV = Clamp;
};
struct VertData {
float4 pos : POSITION;
float2 uv : TEXCOORD0;
};
VertData VSDefault(VertData v_in)
{
VertData vert_out;
vert_out.pos = mul(float4(v_in.pos.xyz, 1.0), ViewProj);
vert_out.uv = v_in.uv;
return vert_out;
}
float4 pixel(float2 uv)
{
return image.Sample(textureSampler, uv);
}
float4 DrawLowresBilinear(VertData v_in)
{
float2 uv = v_in.uv;
float2 stepxy = float2(ddx(uv.x), ddy(uv.y));
float2 stepxy1 = stepxy * 0.0625;
float2 stepxy3 = stepxy * 0.1875;
float2 stepxy5 = stepxy * 0.3125;
float2 stepxy7 = stepxy * 0.4375;
// Simulate Direct3D 8-sample pattern
float4 out_color;
out_color = pixel(uv + float2( stepxy1.x, -stepxy3.y));
out_color += pixel(uv + float2(-stepxy1.x, stepxy3.y));
out_color += pixel(uv + float2( stepxy5.x, stepxy1.y));
out_color += pixel(uv + float2(-stepxy3.x, -stepxy5.y));
out_color += pixel(uv + float2(-stepxy5.x, stepxy5.y));
out_color += pixel(uv + float2(-stepxy7.x, -stepxy1.y));
out_color += pixel(uv + float2( stepxy3.x, stepxy7.y));
out_color += pixel(uv + float2( stepxy7.x, -stepxy7.y));
return out_color * 0.125;
}
float4 PSDrawLowresBilinearRGBA(VertData v_in) : TARGET
{
return DrawLowresBilinear(v_in);
}
float4 PSDrawLowresBilinearRGBADivide(VertData v_in) : TARGET
{
float4 rgba = DrawLowresBilinear(v_in);
float alpha = rgba.a;
float multiplier = (alpha > 0.0) ? (1.0 / alpha) : 0.0;
return float4(rgba.rgb * multiplier, alpha);
}
technique Draw
{
pass
{
vertex_shader = VSDefault(v_in);
pixel_shader = PSDrawLowresBilinearRGBA(v_in);
}
}
technique DrawAlphaDivide
{
pass
{
vertex_shader = VSDefault(v_in);
pixel_shader = PSDrawLowresBilinearRGBADivide(v_in);
}
}