Android > image process > convert image to byte array, convert byte array to image

April 8, 2012   ·   0 Comments

import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.util.Iterator;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
public class ConvertImage {
    public static void main(String[] args) throws FileNotFoundException, IOException {
    	 * In this function the first part shows how to convert an image file to 
    	 * byte array. The second part of the code shows how to change byte array
    	 * back to a image.
        File file = new File("C:\\rose.jpg");
        System.out.println(file.exists() + "!!");
        FileInputStream fis = new FileInputStream(file);
        //create FileInputStream which obtains input bytes from a file in a file system
        //FileInputStream is meant for reading streams of raw bytes such as image data. For reading streams of characters, consider using FileReader.
        //InputStream in = resource.openStream();
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        byte[] buf = new byte[1024];
        try {
            for (int readNum; (readNum = != -1;) {
                bos.write(buf, 0, readNum); 
                //no doubt here is 0
                /*Writes len bytes from the specified byte array starting at offset 
                off to this byte array output stream.*/
                System.out.println("read " + readNum + " bytes,");
        } catch (IOException ex) {
            Logger.getLogger(ConvertImage.class.getName()).log(Level.SEVERE, null, ex);
        byte[] bytes = bos.toByteArray();
        //bytes is the ByteArray we need
         * The second part shows how to convert byte array back to an image file  
        //Before is how to change ByteArray back to Image
        ByteArrayInputStream bis = new ByteArrayInputStream(bytes);
        Iterator<?> readers = ImageIO.getImageReadersByFormatName("jpg");
        //ImageIO is a class containing static convenience methods for locating ImageReaders
        //and ImageWriters, and performing simple encoding and decoding. 
        ImageReader reader = (ImageReader);
        Object source = bis; // File or InputStream, it seems file is OK
        ImageInputStream iis = ImageIO.createImageInputStream(source);
        //Returns an ImageInputStream that will take its input from the given Object
        reader.setInput(iis, true);
        ImageReadParam param = reader.getDefaultReadParam();
        Image image =, param);
        //got an image file
        BufferedImage bufferedImage = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_RGB);
        //bufferedImage is the RenderedImage to be written
        Graphics2D g2 = bufferedImage.createGraphics();
        g2.drawImage(image, null, null);
        File imageFile = new File("C:\\newrose2.jpg");
        ImageIO.write(bufferedImage, "jpg", imageFile);
        //"jpg" is the format of the image
        //imageFile is the file to be written to.
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