diptoblack: add curve controls to shader

app/shaders/diptoblack.frag

@@ -1,8 +1,13 @@
+#define LINEAR_CURVE 0
+#define EXPONENTIAL_CURVE 1
+#define LOGARITHMIC_CURVE 2
+
 uniform sampler2D out_block_in;
 uniform sampler2D in_block_in;
 uniform bool out_block_in_enabled;
 uniform bool in_block_in_enabled;
 uniform vec4 color_in;
+uniform int curve_in;
 
 uniform float ove_tprog_all;
 uniform float ove_tprog_out;
@@ -11,17 +16,27 @@ uniform float ove_tprog_in;
 in vec2 ove_texcoord;
 out vec4 frag_color;
 
+float TransformCurve(float linear) {
+    if (curve_in == EXPONENTIAL_CURVE) {
+        return linear * linear;
+    } else if (curve_in == LOGARITHMIC_CURVE) {
+        return sqrt(linear);
+    } else {
+        return linear;
+    }
+}
+
 void main(void) {
     if (out_block_in_enabled && in_block_in_enabled) {
         // mix(x, y , a): a(1-x) + b(x)
-        vec4 out_block_col = mix(color_in, texture(out_block_in, ove_texcoord),ove_tprog_out);
-        vec4 in_block_col = mix(color_in, texture(in_block_in, ove_texcoord), ove_tprog_in);
+        vec4 out_block_col = mix(color_in, texture(out_block_in, ove_texcoord),TransformCurve(ove_tprog_out));
+        vec4 in_block_col = mix(color_in, texture(in_block_in, ove_texcoord), TransformCurve(ove_tprog_in));
 
         frag_color = out_block_col + in_block_col;
     } else if (out_block_in_enabled) {
-        frag_color = mix(texture(out_block_in, ove_texcoord), color_in, ove_tprog_all);
+        frag_color = mix(texture(out_block_in, ove_texcoord), color_in, TransformCurve(ove_tprog_all));
     } else if (in_block_in_enabled) {
-        frag_color = mix(texture(in_block_in, ove_texcoord), color_in, 1.0 - ove_tprog_all);
+        frag_color = mix(texture(in_block_in, ove_texcoord), color_in, TransformCurve(1.0 - ove_tprog_all));
     } else {
         frag_color = vec4(0.0);
     }