function preload() {
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_01.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_02.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_03.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_04.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_05.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_06.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_07.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_08.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_09.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_10.png'));
  layer1Images.push(loadImage('../../data/P_4_2_1_footage/layer1_11.png'));

  layer2Images.push(loadImage('../../data/P_4_2_1_footage/layer2_01.png'));
  layer2Images.push(loadImage('../../data/P_4_2_1_footage/layer2_02.png'));
  layer2Images.push(loadImage('../../data/P_4_2_1_footage/layer2_03.png'));
  layer2Images.push(loadImage('../../data/P_4_2_1_footage/layer2_04.png'));
  layer2Images.push(loadImage('../../data/P_4_2_1_footage/layer2_05.png'));

  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_01.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_02.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_03.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_04.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_05.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_06.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_07.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_08.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_09.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_10.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_11.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_12.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_13.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_14.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_15.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_16.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_17.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_18.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_19.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_20.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_21.png'));
  layer3Images.push(loadImage('../../data/P_4_2_1_footage/layer3_22.png'));
}
collage generator. example footage can be found in "P_4_2_1_footage".
if you use your own footage, make sure to rename the files or adjust the prefixes:
see the parameters of generateCollageItems()

KEYS
1-3                  : create a new collage (layer specific)
s                    : save png