Working asinh stretch

image.frag

@@ -6,9 +6,16 @@ uniform vec2 scale;
 uniform float a;
 uniform int stretch;
 
+float asinh_(float x)
+{
+    return log(x + sqrt(x*x + 1.0f));
+}
+
 void main(void)
 {
     vec4 color = texture2D(qt_Texture0, qt_TexCoord0);
+    color = color*scale.x + scale.y;
+    max(color, vec4(0.0f));
 
     switch(stretch)
     {
@@ -25,13 +32,15 @@ void main(void)
         break;
     case 4:
     {
-        float l = color.r*0.2126f + color.g*0.7152f + color.b*0.7152f;
-        color *= asinh(l / a) / asinh(1 / a);
+        //float l = color.r*0.2126f + color.g*0.7152f + color.b*0.0722f;
+        float l = (color.r+color.g+color.b)*0.33333f;
+        float k = asinh(l*a)/(l*asinh(a));
+        color *= k;
     }
         break;
     }
 
-    color = color*scale.x + scale.y;
+    //color = color*scale.x + scale.y;
     //float color = pow(c, 0.4545);
     gl_FragColor = color;
 }