Added green screen

shaders/greenscreen-key/shader.json

@@ -0,0 +1,90 @@
+{
+  "id": "greenscreen-key",
+  "name": "Greenscreen Key",
+  "description": "Keys out a green screen background and outputs transparent alpha for compositing.",
+  "category": "Built-in",
+  "entryPoint": "shadeVideo",
+  "parameters": [
+    {
+      "id": "screenColor",
+      "label": "Screen Color",
+      "type": "color",
+      "default": [0.15, 0.85, 0.2, 1.0],
+      "min": [0.0, 0.0, 0.0, 0.0],
+      "max": [1.0, 1.0, 1.0, 1.0],
+      "step": [0.01, 0.01, 0.01, 0.01]
+    },
+    {
+      "id": "threshold",
+      "label": "Threshold",
+      "type": "float",
+      "default": 0.24,
+      "min": 0.01,
+      "max": 0.8,
+      "step": 0.005
+    },
+    {
+      "id": "softness",
+      "label": "Softness",
+      "type": "float",
+      "default": 0.12,
+      "min": 0.001,
+      "max": 0.5,
+      "step": 0.005
+    },
+    {
+      "id": "edgeSoftness",
+      "label": "Edge Softness",
+      "type": "float",
+      "default": 0.08,
+      "min": 0.0,
+      "max": 0.4,
+      "step": 0.005
+    },
+    {
+      "id": "erodeDilate",
+      "label": "Erode/Dilate",
+      "type": "float",
+      "default": 0.0,
+      "min": -0.3,
+      "max": 0.3,
+      "step": 0.005
+    },
+    {
+      "id": "despill",
+      "label": "Despill",
+      "type": "float",
+      "default": 0.45,
+      "min": 0.0,
+      "max": 1.5,
+      "step": 0.01
+    },
+    {
+      "id": "edgeBoost",
+      "label": "Edge Boost",
+      "type": "float",
+      "default": 0.08,
+      "min": -0.2,
+      "max": 0.3,
+      "step": 0.005
+    },
+    {
+      "id": "clipBlack",
+      "label": "Clip Black",
+      "type": "float",
+      "default": 0.0,
+      "min": 0.0,
+      "max": 0.5,
+      "step": 0.005
+    },
+    {
+      "id": "clipWhite",
+      "label": "Clip White",
+      "type": "float",
+      "default": 1.0,
+      "min": 0.5,
+      "max": 1.0,
+      "step": 0.005
+    }
+  ]
+}

shaders/greenscreen-key/shader.slang

@@ -0,0 +1,40 @@
+float3 safeNormalize(float3 value)
+{
+	float len = max(length(value), 0.0001);
+	return value / len;
+}
+
+float luma709(float3 color)
+{
+	return dot(color, float3(0.2126, 0.7152, 0.0722));
+}
+
+float4 shadeVideo(ShaderContext context)
+{
+	float4 src = context.sourceColor;
+	float3 color = saturate(src.rgb);
+
+	float3 keyColor = safeNormalize(max(screenColor.rgb, float3(0.0001, 0.0001, 0.0001)));
+	float3 sampleColor = safeNormalize(max(color, float3(0.0001, 0.0001, 0.0001)));
+
+	float chromaDistance = length(sampleColor - keyColor);
+	float matteCenter = threshold - erodeDilate;
+	float matteFeather = max(softness + edgeSoftness, 0.0005);
+	float alpha = smoothstep(matteCenter - matteFeather, matteCenter + matteFeather, chromaDistance);
+
+	alpha = saturate((alpha - clipBlack) / max(clipWhite - clipBlack, 0.0001));
+	alpha = saturate(alpha + edgeBoost);
+
+	float greenExcess = max(0.0, color.g - max(color.r, color.b));
+	float spillReduction = greenExcess * despill;
+
+	float3 despilled = color;
+	despilled.g = max(0.0, despilled.g - spillReduction);
+
+	float neutral = luma709(despilled);
+	despilled.rb += spillReduction * 0.25;
+	despilled = lerp(float3(neutral, neutral, neutral), despilled, 0.92);
+
+	float3 premultiplied = saturate(despilled) * alpha;
+	return float4(premultiplied, alpha);
+}