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video-shader-toys/shaders/text-overlay/shader.slang
Aiden e59677c212
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Typography improvements
2026-05-06 13:16:02 +10:00

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float alphaOver(float baseAlpha, float overAlpha)
{
return overAlpha + baseAlpha * (1.0 - overAlpha);
}
float4 compositeOver(float4 baseColor, float4 overColor)
{
float outAlpha = alphaOver(baseColor.a, overColor.a);
float3 outRgb = overColor.rgb + baseColor.rgb * (1.0 - overColor.a);
return float4(outRgb, outAlpha);
}
float sdfCoverage(float2 uv, float edge, float aa)
{
float distance = sampleTitleText(uv);
return smoothstep(edge - aa, edge + aa, distance);
}
float4 shadeVideo(ShaderContext context)
{
float2 resolution = max(context.outputResolution, float2(1.0, 1.0));
float aspect = resolution.x / resolution.y;
float2 textSize = float2(0.72 * scale, 0.09 * scale * aspect);
float2 safeTextSize = max(textSize, float2(0.0001, 0.0001));
float2 textUv = (context.uv - position) / safeTextSize;
bool insideTextRect = textUv.x >= 0.0 && textUv.x <= 1.0 && textUv.y >= 0.0 && textUv.y <= 1.0;
float distance = insideTextRect ? sampleTitleText(textUv) : 0.0;
float edge = 0.5;
float aa = max(fwidth(distance) * (1.75 + softness * 5.0), 0.0025);
float2 pixelTextUv = (1.0 / resolution) / safeTextSize;
float2 sampleOffset = pixelTextUv * 0.38;
float fill = (
sdfCoverage(textUv, edge, aa) * 2.0 +
sdfCoverage(textUv + float2(sampleOffset.x, sampleOffset.y), edge, aa) +
sdfCoverage(textUv + float2(-sampleOffset.x, sampleOffset.y), edge, aa) +
sdfCoverage(textUv + float2(sampleOffset.x, -sampleOffset.y), edge, aa) +
sdfCoverage(textUv + float2(-sampleOffset.x, -sampleOffset.y), edge, aa)) / 6.0;
float outlineDistance = outlineWidth * 0.16;
float outlineEdge = edge - outlineDistance;
float outline = (
sdfCoverage(textUv, outlineEdge, aa) * 2.0 +
sdfCoverage(textUv + float2(sampleOffset.x, sampleOffset.y), outlineEdge, aa) +
sdfCoverage(textUv + float2(-sampleOffset.x, sampleOffset.y), outlineEdge, aa) +
sdfCoverage(textUv + float2(sampleOffset.x, -sampleOffset.y), outlineEdge, aa) +
sdfCoverage(textUv + float2(-sampleOffset.x, -sampleOffset.y), outlineEdge, aa)) / 6.0;
float outlineAlpha = saturate(outline - fill) * outlineColor.a;
float fillAlpha = fill * fillColor.a;
float textAlpha = max(fillAlpha, outlineAlpha);
if (textAlpha <= 0.0001)
return context.sourceColor;
float4 base = context.sourceColor;
float4 outlineLayer = float4(outlineColor.rgb * outlineAlpha, outlineAlpha);
float4 fillLayer = float4(fillColor.rgb * fillAlpha, fillAlpha);
return saturate(compositeOver(compositeOver(base, outlineLayer), fillLayer));
}