How can i rotate a PNG photo and keep the transparent background?

Question

current i use this method to rotate a photo, but the transparent background is lost.
what can I do ?
public CreateRotationPhoto(String photofile,String filetype,int rotation_value,String desfile){
             File fileIn = new File(photofile);
           if (!fileIn.exists()) {
               System.out.println(" file not exists!");
               return;
           try {
                   InputStream input = new FileInputStream(fileIn);
                   JPEGImageDecoder decoder = JPEGCodec.createJPEGDecoder(input);
                   BufferedImage imageSrc = decoder.decodeAsBufferedImage();
                   int width = imageSrc.getWidth();
                   int height = imageSrc.getHeight();
                   BufferedImage src = ImageIO.read(input);
                   int width = src.getWidth(); //????? 
                        int height = src.getHeight(); //????? 
                   Image img = src.getScaledInstance(width, height,
                           Image.SCALE_FAST);
                   BufferedImage bi;
                   int fill_width=0;
                   int fill_height=0;
                   if (rotation_value==1||rotation_value==3){
                        bi = new BufferedImage(height, width,BufferedImage.TYPE_INT_RGB);
                        fill_width=height;
                        fill_height=width;
                   else{
                        bi = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
                        fill_height=height;
                        fill_width=width;
                        //BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
                   input.close();
                   System.out.println(photofile);
                   File fileOut = new File(desfile);
                   //File fileOut = new File("c:/Host1.PNG");
                   OutputStream output = new FileOutputStream(fileOut);
                   JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(output);
                   JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(bi);
                   param.setQuality(0.90f, false);
                   encoder.setJPEGEncodeParam(param);
                   Graphics2D biContext =bi.createGraphics();
                  biContext.setColor(Color.white);
                   biContext.fillRect(0,0,fill_width,fill_height);
                   int frame_width,frame_height;
                 if (rotation_value==1||rotation_value==3){
                        frame_width=height;
                        frame_height=width;
                   }else{
                        frame_width=width;
                        frame_height=height;
                   int x=0,y=0;
                   if (rotation_value==2){
                        x=frame_width;
                        y=frame_height;
                   if (rotation_value==0){
                         x=frame_width;
                         y=frame_height;
                   if (rotation_value==1){
                            x=frame_height;
                             y=frame_height;
                   if (rotation_value==3){
                                x=frame_width;
                             y=frame_width;
                   double rotate=0;
                   if (rotation_value==0){
                         rotate=Math.PI *2;
                   if (rotation_value==1){
                        rotate=Math.PI / 2;
                   if (rotation_value==2){
                        rotate=Math.PI;
                   if (rotation_value==3){
                        rotate=Math.PI*1.5;
                   int x=0,y=0;
                   if (rotation_value==2){
                        x=width;
                        y=height;
                   if (rotation_value==1){
                            x=height;
                             y=height;
                   if (rotation_value==3){
                                x=width;
                             y=width;
                   double rotate=0;
                   if (rotation_value==1){
                        rotate=Math.PI / 2;
                   if (rotation_value==2){
                        rotate=Math.PI;
                   if (rotation_value==3){
                        rotate=Math.PI*1.5;
                   System.out.println(Integer.toString(x)+"|x|"+Integer.toString(y)+"|y|"+Double.toString(rotate));
                   biContext.rotate(rotate, x / 2, y / 2);
                   biContext.drawImage(src, 0, 0, null);
                   biContext.dispose();
                   System.out.println("123123123123");
                   try{
                           ImageIO.write(bi, filetype, output);
                           //ImageIO.write(bi, filetype, "c:/Host.PNG");
                           output.close();
                      }catch (IOException e) {
                          System.err.println(e);
                  // encoder.encode(bi);
                   //output.close();
            } catch (Exception e) {
                     e.printStackTrace();
      }

Answer 1

Using this BufferedImage.TYPE_INT_RGB for the type will eliminate any transparency in
your image. Try BufferedImage.TYPE_INT_ARGB.
Image file: Bird.gif
import java.awt.*;
import java.awt.event.*;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.event.*;
public class Rotate implements ChangeListener
    BufferedImage image;
    JLabel label;
    JSlider slider;
    public Rotate(BufferedImage orig)
        // make transparent background
        Color toErase = new Color(248, 248, 248, 255);
        image = eraseColor(convertImage(orig), toErase);
    public void stateChanged(ChangeEvent e)
        int value = slider.getValue();
        double theta = Math.toRadians(value);
        BufferedImage rotated = getImage(theta);
        label.setIcon(new ImageIcon(rotated));
    private BufferedImage getImage(double theta)
        double cos = Math.cos(theta);
        double sin = Math.sin(theta);
        int w = image.getWidth();
        int h = image.getHeight();
        int width  = (int)(Math.abs(w * cos) + Math.abs(h * sin));
        int height = (int)(Math.abs(w * sin) + Math.abs(h * cos));
        BufferedImage bi = new BufferedImage(width, height, image.getType());
        Graphics2D g2 = bi.createGraphics();
        g2.setPaint(new Color(0,0,0,0));
        g2.fillRect(0,0,width,height);
        AffineTransform at = AffineTransform.getRotateInstance(theta, width/2, height/2);
        double x = (width - w)/2;
        double y = (height - h)/2;
        at.translate(x, y);
        g2.drawRenderedImage(image, at);
        g2.dispose();
        return bi;
    private BufferedImage convertImage(BufferedImage in)
        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
        GraphicsDevice gd = ge.getDefaultScreenDevice();
        GraphicsConfiguration gc = gd.getDefaultConfiguration();
        BufferedImage out = gc.createCompatibleImage(in.getWidth(), in.getHeight(),
                                                     Transparency.TRANSLUCENT);
        Graphics2D g2 = out.createGraphics();
        g2.drawImage(in, 0, 0, null);
        g2.dispose();
        return out;
    private BufferedImage eraseColor(BufferedImage source, Color color)
        int w = source.getWidth();
        int h = source.getHeight();
        int type = BufferedImage.TYPE_INT_ARGB;
        BufferedImage out = new BufferedImage(w, h, type);
        Graphics2D g2 = out.createGraphics();
        g2.setPaint(new Color(0,0,0,0));
        g2.fillRect(0,0,w,h);
        int target = color.getRGB();
        for(int j = 0; j < w*h; j++)
            int x = j % w;
            int y = j / w;
            if(source.getRGB(x, y) == target)
                source.setRGB(x, y, 0);
        g2.drawImage(source, 0, 0, null);
        g2.dispose();
        return out;
    private JLabel getLabel()
        label = new JLabel(new ImageIcon(image));
        return label;
    private JSlider getSlider()
        slider = new JSlider(JSlider.HORIZONTAL, 0, 360, 0);
        slider.addChangeListener(this);
        return slider;
    public static void main(String[] args) throws IOException
        String path = "images/Bird.gif";
        ClassLoader cl = Rotate.class.getClassLoader();
        InputStream is = cl.getResourceAsStream(path);
        Rotate rotate = new Rotate(ImageIO.read(is));
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().setBackground(Color.pink);
        f.getContentPane().add(rotate.getLabel());
        f.getContentPane().add(rotate.getSlider(), "South");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
}