PImage painting;
PImage blurred; // to speed things up
PImage maskImage; 

int lastX, lastY;

void setup()
{
  println("George Pollard – Assignment 2 – Image Processing");
  
  painting = loadImage("/home/porges/Desktop/processing work/escher/data/mask.png"); 
  maskImage = loadImage("/home/porges/Desktop/processing work/escher/data/escher.jpg"); 
  
  size(painting.width, painting.height);
  
  //cache a blurred version
  image(painting, 0, 0);
  filter(BLUR,8);
  blurred = get();
  
  //only update when told to by the mouse
  frameRate(0);
}

void draw()
{ 
  int x1 = mouseX - maskImage.width/2;
  int y1 = mouseY - maskImage.height/2;
   
  x1 = clamp(x1, 0, width - maskImage.width);
  y1 = clamp(y1, 0, height - maskImage.height);
  
  //Only blit the needed part; save the planet!
  mix(blurred, lastX, lastY, lastX, lastY, maskImage.width, maskImage.height,false);
  //image(blurred,0,0);
  
  PImage glass = painting.get(x1,y1,maskImage.width, maskImage.height);
  
  /* Mask it; */
  for (int x = 0; x < maskImage.width; x++)
  for (int y = 0; y < maskImage.height; y++)
    {
      glass.set(x,y, color(
                       red(glass.get(x,y)),
                       green(glass.get(x,y)),
                       blue(glass.get(x,y)),
                       red(maskImage.get(x,y))
                )); 
    }
  
  mix(glass, 0, 0, x1, y1, maskImage.width, maskImage.height, true);
  
  lastX = x1;
  lastY = y1;
}

void mouseMoved()
{
    redraw();
}

void mix(PImage img, int x1, int y1, int x2, int y2, int w, int h, boolean alphaPresent)
{
  if (alphaPresent)
    blend(img, x1, y1, w, h, x2, y2, w, h, BLEND);
  else
    copy(img, x1, y1, w, h, x2, y2, w, h);
}

int clamp(int val, int low, int high)
{
  return val <= low ? low : val >= high ? high : val;
}