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PresenterConsole/assets/shader/ascii.shader

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+// #type vertex
+#version 460 core
+
+layout (location = 0) in vec2 aPos;
+layout (location = 1) in vec2 aUV;
+
+layout (location = 0) out vec2 oUV;
+
+void main()
+{
+    oUV = aUV;
+    gl_Position = vec4(aPos, 0.0, 1.0);
+}
+
+// #type fragment
+#version 460 core
+
+precision highp float;
+
+// All components are in the range [0…1], including hue.
+vec3 rgb2hsv(vec3 c)
+{
+    vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
+    vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
+    vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));
+
+    float d = q.x - min(q.w, q.y);
+    float e = 1.0e-10;
+    return vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
+}
+
+// 16 Windows color palette (approximated)
+const vec3 windowsPalette[7] = vec3[](
+vec3(rgb2hsv(vec3(0.0, 0.0, 1.0)).rg, 0.0), // Blue (FOREGROUND_BLUE)
+vec3(rgb2hsv(vec3(0.0, 1.0, 0.0)).rg, 0.0), // Green (FOREGROUND_GREEN)
+vec3(rgb2hsv(vec3(0.0, 1.0, 1.0)).rg, 0.0), // Cyan (FOREGROUND_GREEN | FOREGROUND_BLUE)
+vec3(rgb2hsv(vec3(1.0, 0.0, 0.0)).rg, 0.0), // Red (FOREGROUND_RED)
+vec3(rgb2hsv(vec3(1.0, 0.0, 1.0)).rg, 0.0), // Magenta (FOREGROUND_RED | FOREGROUND_BLUE)
+vec3(rgb2hsv(vec3(1.0, 1.0, 0.0)).rg, 0.0), // Yellow (FOREGROUND_RED | FOREGROUND_GREEN)
+vec3(rgb2hsv(vec3(1.0, 1.0, 1.0)).rg, 0.0)  // White (all colors set)
+);
+
+// Find the closest color in the Windows palette
+int findClosestColor(vec3 color) {
+    int closestIndex = 0;
+    float minDistance = distance(color, windowsPalette[0]);
+
+    for (int i = 1; i < 7; i++) {
+        float dist = distance(color, windowsPalette[i]);
+        if (dist < minDistance) {
+            minDistance = dist;
+            closestIndex = i;
+        }
+    }
+
+    return closestIndex + 1;
+}
+
+float calculateLuminosity(vec3 color) {
+    // Standard luminosity calculation
+    float luminosity = dot(color, vec3(0.299, 0.587, 0.114));
+    return clamp(luminosity, 0.0, 1.0);
+}
+
+uniform sampler2D uInputTexture;
+
+layout (location = 0) in vec2 iUV;
+layout (location = 0) out vec4 FragColor;
+
+void main() {
+    vec3 pixelColor = texture(uInputTexture, iUV).rgb;
+    vec3 pixelColorHsv = rgb2hsv(pixelColor);
+
+    // Find closest color index (4 bits)
+    int colorIndex = findClosestColor(vec3(pixelColorHsv.rg, 0));
+
+    // Calculate luminosity (4 bits)
+    float luminosity = calculateLuminosity(pixelColor);
+
+    // Combine into a single byte-like value
+    // High 4 bits: color index
+    // Low 4 bits: luminosity
+    FragColor = vec4(luminosity, colorIndex / 255.0, 0, 1);
+}