first commit

ghostty/shaders/dither.glsl

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+// Simple "dithering" effect
+// (c) moni-dz (https://github.com/moni-dz)
+// CC BY-NC-SA 4.0 (https://creativecommons.org/licenses/by-nc-sa/4.0/)
+
+// Packed bayer pattern using bit manipulation
+const float bayerPattern[4] = float[4](
+    0x0514, // Encoding 0,8,2,10
+    0xC4E6, // Encoding 12,4,14,6
+    0x3B19, // Encoding 3,11,1,9
+    0xF7D5  // Encoding 15,7,13,5
+);
+
+float getBayerFromPacked(int x, int y) {
+    int idx = (x & 3) + ((y & 3) << 2);
+    return float((int(bayerPattern[y & 3]) >> ((x & 3) << 2)) & 0xF) * (1.0 / 16.0);
+}
+
+#define LEVELS 2.0 // Available color steps per channel
+#define INV_LEVELS (1.0 / LEVELS)
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord)
+{
+    vec2 uv = fragCoord * (1.0 / iResolution.xy);
+    vec3 color = texture(iChannel0, uv).rgb;
+ 
+    float threshold = getBayerFromPacked(int(fragCoord.x), int(fragCoord.y));
+    vec3 dithered = floor(color * LEVELS + threshold) * INV_LEVELS;
+
+    fragColor = vec4(dithered, 1.0);
+}