How do I go from an array of pixel values to an image file in Java?

Question

I have some code that generates an image (a 2-d array of 8-bit grayscale values, but could be anything).

I want to export this image as a .png file.

Which path should I follow? I'm really confused by javax.imageio and java.awt.Image.

Answer 1

Actually you need java.awt.image.BufferedImage as the image object, so you can use setRGB to set RGB value in a given (x,y) coordinate. But to save you image as file you might want to use javax.imageio.ImageIO .

Here is a small example to emphasize how to use them both:

int[][] img = getImage();

int xLenght = img.length;
int yLength = img[0].length;

//java.awt.image.BufferedImage:
BufferedImage bi = new BufferedImage(xLenght, yLength, BufferedImage.TYPE_INT_BGR);

for(int x = 0; x < xLenght; x++) {
    for(int y = 0; y < yLength; y++) {
        int rgbPixel = (int)img[x][y]<<16 | (int)img[x][y] << 8 | (int)img[x][y];
                bi.setRGB(x, y, rgb);
    }
}
try {
    // javax.imageio.ImageIO:
    ImageIO.write(bi, "myImage", new File("myImage.png"));
} catch (IOException e) {
    e.printStackTrace();
}