gistfile1.pde

import com.sun.image.codec.jpeg.*; 

ByteArrayOutputStream out = null;
BufferedImage img = null;
JPEGImageEncoder encoder = null;
JPEGEncodeParam encpar = null;

void setup() {
  size(200,200);
  out = new ByteArrayOutputStream();
  img = new BufferedImage(1024, 768, BufferedImage.TYPE_USHORT_GRAY);  
  encoder = JPEGCodec.createJPEGEncoder(out); 
  encpar = encoder.getDefaultJPEGEncodeParam(img); 
}

void draw() {
  try {
    makeJpeg(img);
  } catch (Exception e) {
    e.printStackTrace();
  }
}

byte[] makeJpeg(BufferedImage img) throws Exception {
  out.reset();    
  encpar.setQuality(0.7,true); // 0.0-1.0, force baseline 
  encoder.setJPEGEncodeParam(encpar); 
  encoder.encode(img);
  return out.toByteArray();  
}