-// Standard lift/gamma/gain color correction tools.
+// Implicit uniforms:
//
-// We do lift in a nonlinear (gamma-2.2) space since that looks a lot better
-// than in linear (blacks stay a lot closer to black). The two others don't
-// really care; they are (sans some constants) commutative with the x^2.2
-// operation.
-
// These are calculated in the host code to save some arithmetic.
-uniform vec3 PREFIX(gain_pow_inv_gamma); // gain^(1/gamma).
-uniform vec3 PREFIX(inv_gamma_22); // 2.2 / gamma.
+// uniform vec3 PREFIX(gain_pow_inv_gamma); // gain^(1/gamma).
+// uniform vec3 PREFIX(inv_gamma_22); // 2.2 / gamma.
vec4 FUNCNAME(vec2 tc) {
- vec4 x = LAST_INPUT(tc);
+ vec4 x = INPUT(tc);
+
+ x.rgb /= x.aaa;
+
+ // pow() of negative numbers is undefined, so clip out-of-gamut values.
+ x.rgb = max(x.rgb, 0.0);
x.rgb = pow(x.rgb, vec3(1.0/2.2));
x.rgb += PREFIX(lift) * (vec3(1) - x.rgb);
+
+ // Clip out-of-gamut values again.
+ x.rgb = max(x.rgb, 0.0);
+
x.rgb = pow(x.rgb, PREFIX(inv_gamma_22));
x.rgb *= PREFIX(gain_pow_inv_gamma);
+ x.rgb *= x.aaa;
return x;
}