final String PATH = "D:/_PhiLhoDocs/Images/";
final int IMAGE_NB = 5;
final color TINT = 255  / IMAGE_NB;

void setup()
{
noLoop();
PImage pi = loadImage(PATH + "HPIM1592.JPG");
AddTransparency(pi, TINT);
// Dimension to image size
size(pi.width,  pi.height);
// Display whole image
image(pi, 0, 0);

pi = loadImage(PATH + "HPIM1593.JPG");
AddTransparency(pi, TINT);
blend(pi, 0, 0, pi.width,  pi.height, 0, 0, pi.width,  pi.height, LIGHTEST);

pi = loadImage(PATH + "HPIM1595.JPG");
AddTransparency(pi, TINT);
blend(pi, 0, 0, pi.width,  pi.height, 0, 0, pi.width,  pi.height, LIGHTEST);

pi = loadImage(PATH + "HPIM1597.JPG");
//AddTransparency(pi, TINT);
blend(pi, 0, 0, pi.width,  pi.height, 0, 0, pi.width,  pi.height, LIGHTEST);

pi = loadImage(PATH + "HPIM1598.JPG");
AddTransparency(pi, TINT);
blend(pi, 0, 0, pi.width,  pi.height, 0, 0, pi.width,  pi.height, LIGHTEST);
}

void AddTransparency(PImage pi, int transparency)
{
  transparency <<= 24;
  for (int i = 0; i < pi.width; i++)
  {
    for (int j = 0; j < pi.height; j++)
    {
	color c = pi.pixels[i + j * pi.width];
	c = c & 0x00FFFFFF | transparency;
	pi.pixels[i + j * pi.width] = c;
    }
  }
}