Convert a 2D array of int ranging from 0-256 into

Question

How can I convert a 2D array of ints into a grayscale png. right now I have this:

    BufferedImage theImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
    for(int y = 0; y<100; y++){
        for(int x = 0; x<100; x++){
            theImage.setRGB(x, y, image[y][x]);
        }
    }
    File outputfile = new File("saved.bmp");
    ImageIO.write(theImage, "png", outputfile);

but the image comes out blue. how can I make it a grayscale.

image[][] contains ints ranging from 0-256.

Answer 1

The image comes out blue because setRGB is expecting an RGB value, you're only setting the low byte, which is probably Blue, which is why it's coming out all blue.

Try:

BufferedImage theImage = new BufferedImage(100, 100, BufferedImage.TYPE_INT_RGB);
for(int y = 0; y<100; y++){
    for(int x = 0; x<100; x++){
        int value = image[y][x] << 16 | image[y][x] << 8 | image[y][x];
        theImage.setRGB(x, y, value);
    }
}

Answer 2

I never tried but actually BufferedImage should be instantiated even in grey scale mode:

new BufferedImage(100, 100, BufferedImage.TYPE_BYTE_GRAY);