43 lines
1.1 KiB
Plaintext
43 lines
1.1 KiB
Plaintext
#include <metal_stdlib>
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using namespace metal;
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struct Uniforms {
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float invert;
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float mode; // 0 = alpha, 1 = binary
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float2 padding;
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};
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struct FragmentIn {
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float4 position [[position]];
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float2 uv;
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};
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fragment float4 fragment_main(
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FragmentIn in [[stage_in]],
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constant Uniforms &uniforms [[buffer(0)]],
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texture2d<float> content_tex [[texture(0)]],
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texture2d<float> mask_tex [[texture(1)]],
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sampler samp [[sampler(0)]]
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) {
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float4 content = content_tex.sample(samp, in.uv);
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float4 mask = mask_tex.sample(samp, in.uv);
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// Get mask value (use alpha channel)
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float mask_value = mask.a;
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// Binary mode: threshold at 0.5
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if (uniforms.mode > 0.5) {
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mask_value = mask_value > 0.5 ? 1.0 : 0.0;
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}
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// Invert if requested
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if (uniforms.invert > 0.5) {
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mask_value = 1.0 - mask_value;
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}
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// Content is premultiplied alpha from render pass blending.
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// Un-premultiply before masking so downstream blit (src_alpha blend) works correctly.
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float3 rgb = content.a > 0.001 ? content.rgb / content.a : float3(0);
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return float4(rgb, content.a * mask_value);
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}
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