resize

PImage a, b, c;

void setup() {
  size(642, 937);
  PImage temp = createImage(width, height, RGB);
  a = loadImage("a.jpg"); // reference image
  b = loadImage("b.jpg");

  if (a.width<a.height) {
    // reference image is portrait mode
    float ratio = (float) a.height/b.height;
    int w = int (b.width*ratio);
    int h = int (b.height*ratio);
    temp.copy(b, 0, 0, b.width, b.height, 0, 0, w, h);
  } else {
    // reference image is landscape mode
    float ratio = (float) a.width/b.width;
    int w = int (b.width*ratio);
    int h = int (b.height*ratio);
    temp.copy(b, 0, 0, b.width, b.height, 0, 0, w, h);
  }
  image(temp, 0, 0);
}

void draw() {
}