Extract image's width, height, color and type from byte array

Question

I have an image in the format of byte[] array in my Java code. I want the following information extracted from that array. How can I do it as fast as possible.

• Width
• Height
• Color (black & white, color or transparent? If color, what is the main color?)
• Type (Is the image PNG, GIF, JPEG, etc.)

Answer 1

Use ImageIO to read as buffered image and then get relevant things which you want. See java doc at http://docs.oracle.com/javase/6/docs/api/javax/imageio/ImageIO.html.

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;

import javax.imageio.ImageIO;


public class Test {

    /**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {
        // assuming that picture is your byte array
        byte[] picture = new byte[30];

        InputStream in = new ByteArrayInputStream(picture);

        BufferedImage buf = ImageIO.read(in);
        ColorModel model = buf.getColorModel();
        int height = buf.getHeight();

    }

}

Answer 2

To get the image type from the byte array, you can do something like:

byte[] picture = new byte[30];
ImageInputStream iis = ImageIO.createImageInputStream(new ByteArrayInputStream(picture));

Iterator<ImageReader> readers = ImageIO.getImageReaders(iis);
while (readers.hasNext()) {
    ImageReader read = readers.next();
    System.out.println("format name = " + read.getFormatName());
}

Here is the output I have for different files:

format name = png
format name = JPEG
format name = gif

It was inspired from:

Convert Byte Array to image in Java - without knowing the type