shader: HSV <-> RGB

hsv_rgb.shader

// https://blog.csdn.net/mobilebbki399/article/details/50603461


float3 RGB2HSV(float3 c)
{
        float4 K = float4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
	float4 p = lerp(float4(c.bg, K.wz), float4(c.gb, K.xy), step(c.b, c.g));
	float4 q = lerp(float4(p.xyw, c.r), float4(c.r, p.yzx), step(p.x, c.r));
 
	float d = q.x - min(q.w, q.y);
	float e = 1.0e-10;
	return float3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
}


float3 HSV2RGB(float3 c)
{
      float4 K = float4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
      float3 p = abs(frac(c.xxx + K.xyz) * 6.0 - K.www);
      return c.z * lerp(K.xxx, saturate(p - K.xxx), c.y);
}