Adding the shader examples

java/examples/Topics/Shaders/EdgeDetect/EdgeDetect.pde

@@ -0,0 +1,31 @@
+/**
+ * Edge Detection
+ * 
+ * Change the default shader to apply a simple, custom edge detection filter.
+ * 
+ * Press the mouse to switch between the custom and default shader.
+ */
+
+PShader edges;  
+PImage img;
+boolean enabled = true;
+    
+void setup() {
+  size(640, 360, P2D);
+  img = loadImage("leaves.jpg");      
+  edges = loadShader("edges.glsl");
+}
+
+void draw() {
+  if (enabled == true) {
+    shader(edges);
+  }
+  image(img, 0, 0);
+}
+    
+void mousePressed() {
+  enabled = !enabled;
+  if (!enabled == true) {
+    resetShader();
+  }
+}

java/examples/Topics/Shaders/EdgeDetect/data/edges.glsl

@@ -0,0 +1,48 @@
+#ifdef GL_ES
+precision mediump float;
+precision mediump int;
+#endif
+
+uniform sampler2D textureSampler;
+uniform vec2 texcoordOffset;
+
+varying vec4 vertColor;
+varying vec4 vertTexcoord;
+
+#define KERNEL_SIZE 9
+
+// Edge detection kernel
+// -1 -1 -1
+// -1 +8 -1
+// -1 -1 -1
+float kernel[KERNEL_SIZE];
+
+vec2 offset[KERNEL_SIZE];
+
+void main(void) {
+    int i = 0;
+    vec4 sum = vec4(0.0);
+
+    offset[0] = vec2(-texcoordOffset.s, -texcoordOffset.t);
+    offset[1] = vec2(0.0, -texcoordOffset.t);
+    offset[2] = vec2(texcoordOffset.s, -texcoordOffset.t);
+
+    offset[3] = vec2(-texcoordOffset.s, 0.0);
+    offset[4] = vec2(0.0, 0.0);
+    offset[5] = vec2(texcoordOffset.s, 0.0);
+
+    offset[6] = vec2(-texcoordOffset.s, texcoordOffset.t);
+    offset[7] = vec2(0.0, texcoordOffset.t);
+    offset[8] = vec2(texcoordOffset.s, texcoordOffset.t);
+
+    kernel[0] = -1.0;   kernel[1] = -1.0;   kernel[2] = -1.0;
+    kernel[3] = -1.0;   kernel[4] = 8.0;    kernel[5] = -1.0;
+    kernel[6] = -1.0;   kernel[7] = -1.0;   kernel[8] = -1.0;
+
+    for(i = 0; i < KERNEL_SIZE; i++) {
+        vec4 tmp = texture2D(textureSampler, vertTexcoord.st + offset[i]);
+        sum += tmp * kernel[i];
+    }
+
+    gl_FragColor = vec4(sum.rgb, 1.0) * vertColor;
+}