Sprite Generator

sprite.pde

import java.util.Arrays;

ArrayList<PImage> images = new ArrayList();
int columns = 12;
int rows = 12;

void setup(){
  selectFolder("Select a folder to process:", "folderSelected");
}

void folderSelected(File selection) {
  if (selection == null) {
    println("Window was closed or the user hit cancel.");
  } else {
    println("User selected " + selection.getAbsolutePath());
    loadImages(selection.getAbsolutePath());
  }
}

void loadImages(String path) {
  File dir = new File(path);
  String[] list = dir.list();
  Arrays.sort(list);
  if (list == null) {
    println("Folder does not exist or cannot be accessed.");
  } 
  else {
    for(int i = 0; i < list.length; i++) {
      if(list[i].indexOf(".") != 0) {
        images.add(loadImage(path + "/" + list[i]));
      }
    }
    createOutputImage();
  }
}

void createOutputImage() {
  PGraphics output = createGraphics(
    images.get(0).width*columns, 
    images.get(0).height*rows
   );
  output.beginDraw();
  for(int i = 0; i < columns; i++) {
    for(int j = 0; j < rows; j++) {
      output.image(
        images.get(i+(12*j)), 
        i*images.get(0).width,
        j*images.get(0).height
       );
    }
  }
  output.endDraw();
  output.save("export.png");
}