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

问题

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.

回答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);
    }
}

回答2:

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

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

来源：https://stackoverflow.com/questions/5436931/convert-a-2d-array-of-int-ranging-from-0-256-into-a-grayscale-png