更新

WPFDark/Controls/Effects/HsvBoxBackgroundEffect.fx

@@ -0,0 +1,22 @@
+float Value : register(C0);
+float IsEnabled : register(C6);
+float3 DisableColor : register(C7);
+
+float4 main(float2 uv : TEXCOORD) : COLOR
+{
+	if (IsEnabled != 0.0f)
+	{
+		float h = uv.x;
+		float s = 1 - uv.y;
+
+        // https://qiita.com/keim_at_si/items/c2d1afd6443f3040e900
+        float3 color = ((clamp(abs(frac(h + float3(0, 2, 1) / 3) * 6 - 3) - 1, 0, 1) - 1) * s + 1) * Value;
+
+		return float4(color, 1);
+	}
+	else
+	{
+		return float4(DisableColor, 1);
+	}
+}
+