Prepare for three channels STF

shaders/thumb.frag

@@ -1,22 +1,22 @@
 #version 330
 
 uniform sampler2DArray qt_Texture0;
-uniform vec3 mtf_param;
+uniform vec3 mtf_param[3];
 uniform bool invert;
 in vec3 qt_TexCoord0;
 layout(location = 0) out vec4 color;
 
-vec4 MTF(vec4 x, vec3 m)
+vec4 MTF(vec4 x, vec4 low, vec4 mid, vec4 high)
 {
-    x = (x - m.x) / (m.z - m.x);
+    x = (x - low) / (high - low);
     x = clamp(x, vec4(0.0), vec4(1.0));
-    return ((m.y - 1) * x) / ((2 * m.y - 1) * x - m.y);
+    return ((mid - 1) * x) / ((2 * mid - 1) * x - mid);
 }
 
 void main(void)
 {
     color = texture(qt_Texture0, qt_TexCoord0);
-    color = MTF(color, mtf_param);
+    color = MTF(color, vec4(mtf_param[0], 0.0), vec4(mtf_param[1], 0.5), vec4(mtf_param[2], 1.0));
     if(invert)color = vec4(1.0) - color;
     color.a = 1.0;
 }