A res/shaders/fish.shader/fish.fs

@@ -0,0 +1,181 @@
+/*
+   fish shader
+   
+   algorithm and original implementation by Miloslav "drummyfish" Ciz
+   (tastyfish@seznam.cz)
+
+   Permission is hereby granted, free of charge, to any person obtaining a copy
+   of this software and associated documentation files (the "Software"), to deal
+   in the Software without restriction, including without limitation the rights
+   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+   copies of the Software, and to permit persons to whom the Software is
+   furnished to do so, subject to the following conditions:
+
+   The above copyright notice and this permission notice shall be included in
+   all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+   THE SOFTWARE.
+*/
+
+precision highp float;
+
+varying vec2 texCoord;
+uniform sampler2D tex;
+uniform vec2 texSize;
+
+uniform float similarity_threshold;
+
+#define screen_res 240,160
+
+vec4 texel_fetch(sampler2D t, ivec2 c)   // because GLSL TexelFetch is not supported
+  {
+    return texture2D(tex,   (2 * vec2(c) + vec2(1,1)) / (2 * vec2(screen_res)) );
+  }
+
+float pixel_brightness(vec4 pixel)
+  {
+    return 0.21 * pixel.x + 0.72 * pixel.y + 0.07 * pixel.z;
+  }
+
+bool pixel_is_brighter(vec4 pixel1, vec4 pixel2)
+  {
+    return pixel_brightness(pixel1) > pixel_brightness(pixel2);
+  }
+
+vec3 pixel_to_yuv(vec4 pixel)
+  {
+    float y = 0.299 * pixel.x + 0.587 * pixel.y + 0.114 * pixel.z;
+    return vec3(y, 0.492 * (pixel.z - y), 0.877 * (pixel.x - y));
+  }
+
+bool yuvs_are_similar(vec3 yuv1, vec3 yuv2)
+  {
+    vec3 yuv_difference = abs(yuv1 - yuv2);
+    return yuv_difference.x <= similarity_threshold && yuv_difference.y <= similarity_threshold && yuv_difference.z <= similarity_threshold;
+  }
+
+bool pixels_are_similar(vec4 pixel1, vec4 pixel2)
+  {
+    vec3 yuv1 = pixel_to_yuv(pixel1);
+    vec3 yuv2 = pixel_to_yuv(pixel2);
+
+    return yuvs_are_similar(yuv1, yuv2);
+  }
+
+vec4 interpolate_nondiagonal(vec4 neighbour1, vec4 neighbour2)
+  {
+    if (pixels_are_similar(neighbour1,neighbour2))
+      return mix(neighbour1,neighbour2,0.5);
+    else
+      return pixel_is_brighter(neighbour1, neighbour2) ? neighbour1 : neighbour2;
+  }
+
+vec4 mix3(vec4 value1, vec4 value2, vec4 value3)
+  {
+    return (value1 + value2 + value3) / 3.0;
+  }
+
+vec4 straight_line(vec4 p0, vec4 p1, vec4 p2, vec4 p3)
+  {
+    return pixel_is_brighter(p2,p0) ? mix(p2,p3,0.5) : mix(p0,p1,0.5);
+  }
+
+vec4 corner(vec4 p0, vec4 p1, vec4 p2, vec4 p3)
+  {
+    return pixel_is_brighter(p1,p0) ? mix3(p1,p2,p3) : mix3(p0,p1,p2);
+  }
+
+vec4 interpolate_diagonal(vec4 a, vec4 b, vec4 c, vec4 d)
+  {
+    // a b
+    // c d
+
+    vec3 a_yuv = pixel_to_yuv(a);
+    vec3 b_yuv = pixel_to_yuv(b);
+    vec3 c_yuv = pixel_to_yuv(c);
+    vec3 d_yuv = pixel_to_yuv(d);
+
+    bool ad = yuvs_are_similar(a_yuv,d_yuv);
+    bool bc = yuvs_are_similar(b_yuv,c_yuv);
+    bool ab = yuvs_are_similar(a_yuv,b_yuv);
+    bool cd = yuvs_are_similar(c_yuv,d_yuv);
+    bool ac = yuvs_are_similar(a_yuv,c_yuv);
+    bool bd = yuvs_are_similar(b_yuv,d_yuv);
+
+    if (ad && cd && ab)                                          // all pixels are equal?
+      return( mix(mix(a,b,0.5), mix(c,d,0.5), 0.5) );
+
+    else if (ac && cd && ! ab)                                   // corner 1?
+      return corner(b,a,d,c);
+    else if (bd && cd && ! ab)                                   // corner 2?
+      return corner(a,b,c,d);
+    else if (ac && ab && ! bd)                                   // corner 3?
+      return corner(d,c,b,a);
+    else if (ab && bd && ! ac)                                   // corner 4?
+      return corner(c,a,d,b);
+
+    else if (ad && (!bc || pixel_is_brighter(b,a)))              // diagonal line 1?
+      return mix(a,d,0.5);
+    else if (bc && (!ad || pixel_is_brighter(a,b)))              // diagonal line 2?
+      return mix(b,c,0.5);
+
+    else if (ab)                                                 // horizontal line 1?
+      return straight_line(a,b,c,d);
+    else if (cd)                                                 // horizontal line 2?
+      return straight_line(c,d,a,b);
+
+    else if (ac)                                                 // horizontal line 3?
+      return straight_line(a,c,b,d);
+    else if (bd)                                                 // horizontal line 4?
+      return straight_line(b,d,a,c);
+
+    return( mix(mix(a,b,0.5), mix(c,d,0.5), 0.5) );
+  }
+
+void main()
+  {
+    ivec2 pixel_coords2 = ivec2(texCoord * vec2(screen_res) * 2);
+    ivec2 pixel_coords = pixel_coords2 / 2;
+
+    bool x_even = mod(pixel_coords2.x,2) == 0;
+    bool y_even = mod(pixel_coords2.y,2) == 0;
+
+    if (x_even)
+      {
+        if (y_even)
+          {
+
+            gl_FragColor = interpolate_diagonal(
+              texel_fetch(tex, pixel_coords + ivec2(-1,-1)),
+              texel_fetch(tex, pixel_coords + ivec2(0,-1)),
+              texel_fetch(tex, pixel_coords + ivec2(-1,0)),
+              texel_fetch(tex, pixel_coords + ivec2(0,0))
+              );
+
+          }
+        else
+          {
+            gl_FragColor = interpolate_nondiagonal
+              (
+                texel_fetch(tex, pixel_coords + ivec2(-1,0)),
+                texel_fetch(tex, pixel_coords)
+              );
+          }
+      }
+    else if (y_even)
+      {
+        gl_FragColor = interpolate_nondiagonal
+          (
+            texel_fetch(tex, pixel_coords + ivec2(0,-1)),
+            texel_fetch(tex, pixel_coords)
+          );
+      }
+    else
+      gl_FragColor = texel_fetch(tex, pixel_coords);
+  }

A res/shaders/fish.shader/manifest.ini

@@ -0,0 +1,16 @@
+[shader]
+name=fish
+author=Drummyfish
+description=Attempts to keep thin lines thin.
+passes=1
+
+[pass.0]
+fragmentShader=fish.fs
+integerScaling=1
+
+[pass.0.uniform.similarity_threshold]
+type=float
+default=0.2
+readableName=Similarity Threshold
+min=0
+max=1