我正在尝试生成随机数组并将它们保存为argb图像。但是，当我这样做的时候，当我打开 .png 图像，图像是空白的，好像它们都有一个0的阿尔法，不管我用什么软件打开它们。这是我目前的代码：

import java.io.*;
import java.text.*;
import java.util.*;
import javax.imageio.ImageIO;
import java.awt.image.*;

public class RandomColour
{
    public static void main(String[] args) {
        int w = 100;
        int h = 100;
        int arr[] = new int[w*h];
        for (int i = 0; i < arr.length; i++) {
            int r = (int) (Math.random() * 254);
            int g = (int) (Math.random() * 254);
            int b = (int) (Math.random() * 254);
            arr[i] = 0xFF000000 | (r << 16) | (g << 8) | b;
        }
        BufferedImage outputImage = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
        WritableRaster raster = outputImage.getRaster();
        raster.setSamples(0, 0, w, h, 0, arr);
        try {
            ImageIO.write(outputImage, "png", new File("output.png"));
        } catch(Exception e){
            System.out.println(e);
        }
        System.out.println("Finished generating a random image.");

    }
}