OpenCV 2.4.4 and Processing

The latest OpenCV 2.4.4 supports the desktop version of Java. We can use the OpenCV functions in the Processing environment. Before we write a library for it, we can temporarily test it by putting the opencv-244.jar and libopencv_java244.dylib into the code folder of your sketch. For Windows, the dll file should go there as well.

And we also need to perform conversion between the PImage and the OpenCV Mat. I do not want to loop through the pixels array to use bitwise operations. In this case, I use the Java BufferedImage and WritableRaster classes with the 8 bits and 4 channels standard format.

Here are the example codes that perform the GaussianBlur and Canny functions.

import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.CvType;
import org.opencv.core.Size;
import java.awt.image.BufferedImage;
import java.awt.image.WritableRaster;
import java.awt.image.Raster;
Capture cap;
int pixCnt;
BufferedImage bm;
PImage img;
void setup() {
  size(640, 480);
  cap = new Capture(this, width, height);
  bm = new BufferedImage(width, height, BufferedImage.TYPE_4BYTE_ABGR);
  img = createImage(width, height, ARGB);
  pixCnt = width*height*4;
void convert(PImage _i) {
  bm.setRGB(0, 0, _i.width, _i.height, _i.pixels, 0, _i.width);
  Raster rr = bm.getRaster();
  byte [] b1 = new byte[pixCnt];
  rr.getDataElements(0, 0, _i.width, _i.height, b1);
  Mat m1 = new Mat(_i.height, _i.width, CvType.CV_8UC4);
  m1.put(0, 0, b1);
  Mat m2 = new Mat(_i.height, _i.width, CvType.CV_8UC1);
  Imgproc.cvtColor(m1, m2, Imgproc.COLOR_BGRA2GRAY);   
  Imgproc.GaussianBlur(m2, m2, new Size(7, 7), 1.5, 1.5);
  Imgproc.Canny(m2, m2, 0, 30, 3, false);
  Imgproc.cvtColor(m2, m1, Imgproc.COLOR_GRAY2BGRA);
  m1.get(0, 0, b1);
  WritableRaster wr = bm.getRaster();
  wr.setDataElements(0, 0, _i.width, _i.height, b1);
  bm.getRGB(0, 0, _i.width, _i.height, img.pixels, 0, _i.width);
void draw() {
  if (cap.available()) {
    image(img, 0, 0);