Add dithering fragment shader

1 files changed, 61 insertions, 0 deletions

diff --git a/resources/dither.frag b/resources/dither.frag
new file mode 100644
index 0000000..6082ceb
--- /dev/null
+++ b/resources/dither.frag
@@ -0,0 +1,61 @@
+#version 330 core
+
+const float pR = 0.299;
+const float pG = 0.587;
+const float pB = 0.114;
+
+const vec3 p = vec3(pR, pG, pB);
+
+float dithering_matrix[64];
+
+in vec2 UV;
+in vec4 gl_FragCoord;
+//in vec2 gl_fragCoord;
+out vec4 color;
+
+uniform sampler2D textureSampler;
+
+void main() {
+    // Normalized pixel coordinates (from 0 to 1)
+    vec2 uv = UV; //iTime + (fragCoord.xy / iResolution.xy);
+    vec2 fragPos = gl_FragCoord.xy;
+
+    vec3 col = texture(textureSampler, UV).rgb;
+
+    vec3 colsqrt = col * col;
+    float luminance = sqrt(dot(p, colsqrt));
+
+    dithering_matrix = float[](
+       0.0, 48.0, 12.0, 60.0,  3.0, 51.0, 15.0, 61.0,
+      32.0, 16.0, 44.0, 28.0, 35.0, 19.0, 47.0, 31.0,
+       8.0, 56.0,  4.0, 52.0, 11.0, 59.0,  7.0, 55.0,
+      40.0, 24.0, 36.0, 20.0, 43.0, 27.0, 39.0, 23.0,
+       2.0, 50.0, 14.0, 62.0,  1.0, 49.0, 13.0, 61.0,
+      34.0, 18.0, 46.0, 30.0, 33.0, 17.0, 45.0, 29.0,
+      10.0, 58.0,  6.0, 54.0,  9.0, 57.0,  5.0, 53.0,
+      42.0, 26.0, 38.0, 22.0, 41.0, 25.0, 37.0, 21.0
+    );
+
+    /* BEGIN PASTE */
+    int x = int(mod(fragPos.x, 8.0));
+    int y = int(mod(fragPos.y, 8.0));
+
+    // index of flat matrix
+    int idx = (x * 8) + y;
+    float dither = dithering_matrix[idx];
+    // normalize the value
+    dither *= (1.0 / 64.0);
+
+    /* END PASTE */
+
+    // Output to screen
+    if (luminance > dither) {
+      color = vec4(col, 1.0);
+    } else {
+      color = vec4(
+          float(0x10) / 255.f, float(0x0a) / 255.f, float(0x33) / 255.f, 1.f
+      );
+
+      //color = vec4(0.0);
+    }
+}