Use gamma-corrected mixing in shaders

Shaders/CRT.fsh

@@ -158,8 +158,5 @@ STATIC vec4 scale(sampler2D image, vec2 position, vec2 input_resolution, vec2 ou
         ret *= output_resolution.y - pixel_position.y;
     }
     
-    // Gamma correction
-    ret = pow(ret, vec4(0.72));
-    
     return ret;
 }

Shaders/HQ2x.fsh

@@ -12,7 +12,7 @@ STATIC vec3 rgb_to_hq_colospace(vec4 rgb)
 STATIC bool is_different(vec4 a, vec4 b)
 {
     vec3 diff = abs(rgb_to_hq_colospace(a) - rgb_to_hq_colospace(b));
-    return diff.x > 0.188 || diff.y > 0.027 || diff.z > 0.031;
+    return diff.x > 0.018 || diff.y > 0.002 || diff.z > 0.005;
 }
 
 #define P(m, r) ((pattern & (m)) == (r))
@@ -84,7 +84,7 @@ STATIC vec4 scale(sampler2D image, vec2 position, vec2 input_resolution, vec2 ou
         return interp_3px(w4, 2.0, w0, 1.0, w3, 1.0);
     }
     if (P(0x2f,0x2f)) {
-        return interp_3px(w4, 1.04, w3, 1.0, w1, 1.0);
+        return interp_3px(w4, 4.0, w3, 1.0, w1, 1.0);
     }
     if (P(0xbf,0x37) || P(0xdb,0x13)) {
         return interp_3px(w4, 5.0, w1, 2.0, w3, 1.0);

Shaders/MasterShader.fsh

@@ -9,14 +9,22 @@ uniform vec2 origin;
 #define equal(x, y) ((x) == (y))
 #define inequal(x, y) ((x) != (y))
 #define STATIC
+#define GAMMA (2.2)
 
 out vec4 frag_color;
 
+vec4 _texture(sampler2D t, vec2 pos)
+{
+    return pow(texture(t, pos), vec4(GAMMA));
+}
+
+#define texture _texture
+
 #line 1
 {filter}
 
 
-#define BLEND_BIAS (1.0/3.0)
+#define BLEND_BIAS (2.0/5.0)
 
 #define DISABLED 0
 #define SIMPLE 1
@@ -58,7 +66,7 @@ void main()
             break;
     }
 
-    frag_color = mix(scale(image, position, input_resolution, output_resolution),
+    frag_color = pow(mix(scale(image, position, input_resolution, output_resolution),
-                     scale(previous_image, position, input_resolution, output_resolution), ratio);
+                         scale(previous_image, position, input_resolution, output_resolution), ratio), vec4(1.0 / GAMMA));
 
 }

Shaders/MasterShader.metal

@@ -12,6 +12,7 @@ typedef texture2d<half> sampler2D;
 #define equal(x, y) all((x) == (y))
 #define inequal(x, y) any((x) != (y))
 #define STATIC static
+#define GAMMA (2.2)
 
 typedef struct {
     float4 position [[position]];
@@ -36,7 +37,7 @@ vertex rasterizer_data vertex_shader(uint index [[ vertex_id ]],
 static inline float4 texture(texture2d<half> texture, float2 pos)
 {
     constexpr sampler texture_sampler;
-    return float4(texture.sample(texture_sampler, pos));
+    return pow(float4(texture.sample(texture_sampler, pos)), GAMMA);
 }
 
 #line 1
@@ -87,7 +88,7 @@ fragment float4 fragment_shader(rasterizer_data in [[stage_in]],
             break;
     }
     
-    return mix(scale(image, in.texcoords, input_resolution, *output_resolution),
+    return pow(mix(scale(image, in.texcoords, input_resolution, *output_resolution),
-               scale(previous_image, in.texcoords, input_resolution, *output_resolution), ratio);
+               scale(previous_image, in.texcoords, input_resolution, *output_resolution), ratio), 1 / GAMMA);
 }
 

Shaders/OmniScale.fsh

@@ -19,7 +19,7 @@ STATIC vec3 rgb_to_hq_colospace(vec4 rgb)
 STATIC bool is_different(vec4 a, vec4 b)
 {
     vec3 diff = abs(rgb_to_hq_colospace(a) - rgb_to_hq_colospace(b));
-    return diff.x > 0.125 || diff.y > 0.027 || diff.z > 0.031;
+    return diff.x > 0.018 || diff.y > 0.002 || diff.z > 0.005;
 }
 
 #define P(m, r) ((pattern & (m)) == (r))