Rework stretch to use just MTF

image.frag

@@ -2,43 +2,22 @@
 
 uniform sampler2D qt_Texture0;
 varying vec2 qt_TexCoord0;
-uniform vec2 scale;
-uniform float a;
-uniform int stretch;
+uniform vec3 mtf_param;
 uniform bool bw;
 
+vec4 MTF(vec4 x, vec3 m)
+{
+    x = (x - m.x) / (m.z - m.x);
+    x = clamp(x, vec4(0.0), vec4(1.0));
+    return ((m.y - 1) * x) / ((2 * m.y - 1) * x - m.y);
+}
+
 void main(void)
 {
     vec4 color = texture2D(qt_Texture0, qt_TexCoord0);
     if(bw)color = color.rrra;
-    color = color*scale.x + scale.y;
-    color = max(color, vec4(0.0f));
+    color = MTF(color, mtf_param);
 
-    switch(stretch)
-    {
-    case 0:
-        break;
-    case 1:
-       color = sqrt(color);
-       break;
-    case 2:
-        color = pow(color, vec4(a));
-        break;
-    case 3:
-        color = log(a*color + 1.0) / log(vec4(a+1));
-        break;
-    case 4:
-    {
-        //float l = color.r*0.2126f + color.g*0.7152f + color.b*0.0722f;
-        float l = (color.r+color.g+color.b)*0.33333;
-        float k = asinh(l*a)/(l*asinh(a));
-        color *= k;
-    }
-        break;
-    }
-
-    //color = color*scale.x + scale.y;
-    //float color = pow(c, 0.4545);
     if(any(lessThan(qt_TexCoord0, vec2(0.0))) || any(greaterThan(qt_TexCoord0, vec2(1.0))))
         color = vec4(0.0);
     gl_FragColor = color;