+ "vec3 rgb2hsl(vec3 c) {\n"
+ "vec4 K = vec4(0.0, -1.0/3.0, 2.0/3.0, -1.0);\n"
+ "vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));\n"
+ "vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));\n"
+ "float d = q.x - min(q.w, q.y);\n"
+ "float e = 1.0e-10;\n"
+ "return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);\n"
+ "}\n"
+ "vec3 hsl2rgb(vec3 c) {\n"
+ "vec4 K = vec4(1.0, 2.0/3.0, 1.0/3.0, 3.0);\n"
+ "vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);\n"
+ "return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);\n"
+ "}\n"