Transparency.

Move the pointer left and right across the image to change
its position. This program overlays one image over another
by modifying the alpha value of the image.

Created 09 December 2002

PImage a, b;
boolean once = false;
int[] buffer;
float bufferOffset, newBufferOffset;

void setup() 
{
  size(200, 200);
  buffer = new int[width*height];
  bufferOffset = newBufferOffset = 0.0;
  a = loadImage("construct.jpg");  // Load an image into the program 
  b = loadImage("wash.jpg");   // Load an image into the program 
  frameRate(60);
}

void draw() 
{ 
  image(a, 0, 0);
  
  newBufferOffset = -b.width/2 + (mouseX*2-width/2);
  float distance = bufferOffset - newBufferOffset;
  if( abs(distance) > 0.01 ) {
    bufferOffset -= distance/10.0;
    bufferOffset = constrain(bufferOffset, -400, 0);
  }
  tint(255, 153);
  image(b, bufferOffset, 20);
}