/*
 * Demonstration of a vignette through masking.
 */

int bands = 255;
float outerSize = 1.2;  // size of outer ellipse, as percentage of full
float innerSize = 0.6;  // size of inner ellipse, as percentage of full

size(408, 300);   // original image is 408x300
PImage slu = loadImage("http://business.slu.edu/uploads/2012/11/08/slu-homepage-campus4.jpg");
int w = slu.width;
int h = slu.height;

// create the mask image
PGraphics mask = createGraphics(w, h);
mask.noSmooth();
mask.beginDraw();
mask.background(0);
mask.noStroke();
for (int j=0; j < bands; j++) {
  mask.fill( map(j, 0, bands-1, 0, 255) );  // gradiant shading
  float scale = map(j, 0, bands-1, outerSize, innerSize);
  mask.ellipse(0.5*w, 0.5*h, scale*w, scale*h);
}
mask.endDraw();

// apply the mask to the original image
slu.mask(mask);

// draw masked image over a black background
background(0);
image(slu, 0, 0);