Why does ImageReader return incorrect BufferedImage?

Question

I\'m trying to access a animated GIF image with 21 frames and then read the 12th (cause it starts at 0?) frame.

import java.awt.image.BufferedImage;
import j         


        

Answer 1

The rectangle in your example appears to be a frame representing the changed portion of the image sequence, starting from 1. Open the file in Gimp to see.

Addendum: It looks like a feature intended to optimize rendering. At a guess, I'd say you could rely on the bounds of image number getMinIndex(); later frames appear to be subsumed in the first.

Addendum:

is there a way to get the full pixel data with the normal image and changes?

Assuming known geometry, you should be able to combine the first image and any later one in a BufferedImage, as shown here.

Code:

import java.awt.image.BufferedImage;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;

public class GifBounds {

    /** @see https://stackoverflow.com/questions/5688104 */
    public static void main(String[] args) throws IOException {
        search(new URL("http://i55.tinypic.com/263veb9.gif"));
    }
    public static void search(URL url) throws IOException {
        try {
            ImageReader reader = ImageIO.getImageReadersBySuffix("gif").next();
            reader.setInput(ImageIO.createImageInputStream(url.openStream()));
            int i = reader.getMinIndex();
            while (true) {
                BufferedImage bi = reader.read(i++);
                System.out.println(i
                    + ": " + bi.getWidth()
                    + ", " + bi.getHeight());
            }

        } catch (IndexOutOfBoundsException e) {
            // ignored
        }
    }
}

Console:

1: 200, 220
2: 79, 95
3: 77, 94
4: 78, 95
5: 79, 95
6: 77, 94
7: 78, 95
8: 79, 95
9: 77, 94
10: 180, 205
11: 97, 111
12: 173, 200
13: 174, 155
14: 174, 155
15: 174, 155
16: 174, 155
17: 174, 155
18: 174, 155
19: 174, 155
20: 167, 200
21: 97, 111