BufferedImage#setRGB で作ってみる。 import java.awt.*; import java.awt.image.*; import java.io.*; import javax.imageio.*; public class AlphaPNG { public static void main(String[] args) throws Exception { int width = 256; int height = 256; Color[] colors = new Color[] { new Color(255, 0, 0), new Color(0, 255, 0), new Color(0, 0, 255), }; BufferedImage image = new BufferedImage(width, height, BufferedImage