Re-adding Topics to SVN

java/examples/Topics/Image Processing/Convolution/Convolution.pde

@@ -0,0 +1,74 @@
+/**
+ * Convolution
+ * by Daniel Shiffman.  
+ * 
+ * Applies a convolution matrix to a portion of the index.  
+ * Move mouse to apply filter to different parts of the image. 
+ */
+
+PImage img;
+int w = 80;
+
+// It's possible to convolve the image with 
+// many different matrices
+
+  float[][] matrix = { { -1, -1, -1 },
+                       { -1,  9, -1 },
+                       { -1, -1, -1 } }; 
+
+void setup() {
+  size(200, 200);
+  frameRate(30);
+  img = loadImage("end.jpg");
+}
+
+void draw() {
+  // We're only going to process a portion of the image
+  // so let's set the whole image as the background first
+  image(img,0,0);
+  // Where is the small rectangle we will process
+  int xstart = constrain(mouseX-w/2,0,img.width);
+  int ystart = constrain(mouseY-w/2,0,img.height);
+  int xend = constrain(mouseX+w/2,0,img.width);
+  int yend = constrain(mouseY+w/2,0,img.height);
+  int matrixsize = 3;
+  loadPixels();
+  // Begin our loop for every pixel
+  for (int x = xstart; x < xend; x++) {
+    for (int y = ystart; y < yend; y++ ) {
+      color c = convolution(x,y,matrix,matrixsize,img);
+      int loc = x + y*img.width;
+      pixels[loc] = c;
+    }
+  }
+  updatePixels();
+}
+
+color convolution(int x, int y, float[][] matrix,int matrixsize, PImage img)
+{
+  float rtotal = 0.0;
+  float gtotal = 0.0;
+  float btotal = 0.0;
+  int offset = matrixsize / 2;
+  for (int i = 0; i < matrixsize; i++){
+    for (int j= 0; j < matrixsize; j++){
+      // What pixel are we testing
+      int xloc = x+i-offset;
+      int yloc = y+j-offset;
+      int loc = xloc + img.width*yloc;
+      // Make sure we haven't walked off our image, we could do better here
+      loc = constrain(loc,0,img.pixels.length-1);
+      // Calculate the convolution
+      rtotal += (red(img.pixels[loc]) * matrix[i][j]);
+      gtotal += (green(img.pixels[loc]) * matrix[i][j]);
+      btotal += (blue(img.pixels[loc]) * matrix[i][j]);
+    }
+  }
+  // Make sure RGB is within range
+  rtotal = constrain(rtotal,0,255);
+  gtotal = constrain(gtotal,0,255);
+  btotal = constrain(btotal,0,255);
+  // Return the resulting color
+  return color(rtotal,gtotal,btotal);
+}
+