Why does java draw wrong color lines on a jpeg image?

Question

I have a simple java program which takes a jpeg image as input, draws a line and a rectangle on that then saves it. I want the lines and rectangle to be red but in result images they are always black,white or grey; it depends on what color i set for the lines.

This is the simple code

 import java.awt.Color;
 import java.awt.Graphics2D;
 import java.awt.image.BufferedImage;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
 import javax.imageio.ImageIO;
 import com.sun.image.codec.jpeg.ImageFormatException;
 import com.sun.image.codec.jpeg.JPEGCodec;

 public class Lines {

public static void main(String[] args) {
    BufferedImage image = null;

    File filePath = new File("C:\\Users\\agelormini\\Desktop\\big.jpg");
    com.sun.image.codec.jpeg.JPEGImageDecoder jpegDecoder = null;
    try {
        jpegDecoder = JPEGCodec.createJPEGDecoder (new FileInputStream(filePath));
    } catch (FileNotFoundException e2) {
        e2.printStackTrace();
    }

    try {
        image = jpegDecoder.decodeAsBufferedImage();
    } catch (ImageFormatException e1) {
        e1.printStackTrace();
    } catch (IOException e1) {
        e1.printStackTrace();
    }

    Graphics2D g2d = image.createGraphics();
    g2d.setColor(Color.RED);
    g2d.drawLine(131, 220, 216, 222);
    g2d.drawRect(164, 157, 268 - 164, 287 - 157);
    g2d.drawLine(165, 229, 174, 135);
    File dest = new File("C:\\Users\\agelormini\\Desktop\\big_mod.jpg");
    try {
        ImageIO.write(image, "jpg", dest);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

In this case lines will be black, with yellow will be white...I don't understand why this happens. Any suggestion?

thanks

Answer 1

I managed to resolve the problem using this little convert function

public static BufferedImage convert(BufferedImage src, int bufImgType) {
    BufferedImage img= new BufferedImage(src.getWidth(), src.getHeight(), bufImgType);
    Graphics2D g2d= img.createGraphics();
    g2d.drawImage(src, 0, 0, null);
    g2d.dispose();
    return img;
}

if i add this line to the previous code just before the Graphics2D creation it works:

   image = convert(image, BufferedImage.TYPE_INT_BGR);

I had to use TYPE_INT_BGR since ARGB resulted in wrong colors of the previous image. I am in win environment so its not a problem

thank you for the help!