Adding Filters

rsc/shaders/filters/halftone.glsl

@@ -0,0 +1,54 @@
+const float PI = 3.1415926535897932384626433832795;
+const float PI180 = float(PI / 180.0);
+
+float sind(float a)
+{
+	return sin(a * PI180);
+}
+
+float cosd(float a)
+{
+	return cos(a * PI180);
+}
+
+float added(vec2 sh, float sa, float ca, vec2 c, float d)
+{
+	return 0.5 + 0.25 * cos((sh.x * sa + sh.y * ca + c.x) * d) + 0.25 * cos((sh.x * ca - sh.y * sa + c.y) * d);
+}
+
+void mainImage( out vec4 fragColor, in vec2 fragCoord )
+{
+	// Halftone dot matrix shader
+	// @author Tomek Augustyn 2010
+	
+	// Ported from my old PixelBender experiment
+	// https://github.com/og2t/HiSlope/blob/master/src/hislope/pbk/fx/halftone/Halftone.pbk
+	
+	// Hold and drag horizontally to adjust the threshold
+
+	float threshold = clamp(float(0.2) + 0.6, 0.0, 1.0);
+
+	float ratio = iResolution.y / iResolution.x;
+	float coordX = fragCoord.x / iResolution.x;
+	float coordY = fragCoord.y / iResolution.x;
+	vec2 dstCoord = vec2(coordX, coordY);
+	vec2 srcCoord = vec2(coordX, coordY / ratio);
+	vec2 rotationCenter = vec2(0.5, 0.5);
+	vec2 shift = dstCoord - rotationCenter;
+	
+	float dotSize = 3.0;
+	float angle = 45.0;
+	
+	float rasterPattern = added(shift, sind(angle), cosd(angle), rotationCenter, PI / dotSize * 680.0);
+	vec4 srcPixel = texture(iChannel0, srcCoord);
+        
+	float avg = 0.2125 * srcPixel.r + 0.7154 * srcPixel.g + 0.0721 * srcPixel.b;
+    float gray = 1.0 - (rasterPattern * threshold + avg - threshold) / (1.0 - threshold);
+
+	// uncomment to see how the raster pattern looks 
+    // gray = rasterPattern;
+    	
+	fragColor = vec4(gray, gray, gray, 1.0);
+}
+    
+