Images can be displayed to the screen at their actual size or any other size.
Original Processing.org Example: Displaying
// All Examples Written by Casey Reas and Ben Fry
// unless otherwise stated.
size(200, 200);
PImage a; // Declare variable "a" of type PImage
a = loadImage("arch.jpg"); // Load the images into the program
image(a, 0, 0); // Displays the image from point (0,0)
image(a, width/2, 0, a.width/2, a.height/2);