How do I load an enormous image to Java via BufferedImage?

问题

I want to load large images (18000 x 18000) to my application. If i use BufferedImage with type int_rgb, I need around 1235mb of heap memory to load. This is a very high amount of memory, and end users will likely have less ram (1GB or less).

On my development PC, when I load the image from MyEclipse IDE, it throws an out of memory Exception. When i pack my code to an executable jar and run it on my PC external of Eclipse, it still throws an exception.

How do I load such a large image into my application using buffered image without using 1235mb of memory? Is there a trick, like splitting the image into smaller portions like image segmentation?

I found this thread on SO, but it not useful for me; I want to load the image into BufferedImage and then draw it on a Panel using the Graphics class.

回答1:

You can read and display fragments of the image using ImageReadParam from ImageIO package. Here is a basic example that illustrates how to read a single fragment using ImageReadParam without reading the whole image:

import java.awt.Image;
import java.awt.Rectangle;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
import javax.imageio.stream.ImageInputStream;
import javax.swing.*;

public class TestImageChunks {
    private static void createAndShowUI() {
        try {
            URL url = new URL(
                    "http://duke.kenai.com/wave/.Midsize/Wave.png.png");
            Image chunk = readFragment(url.openStream(), new Rectangle(150,
                    150, 300, 250));
            JOptionPane.showMessageDialog(null, new ImageIcon(chunk), "Duke", 
                    JOptionPane.INFORMATION_MESSAGE);
        } catch (IOException e) {
            JOptionPane.showMessageDialog(null, e.getMessage(), "Failure",
                    JOptionPane.ERROR_MESSAGE);
            e.printStackTrace();
        }
    }

    public static BufferedImage readFragment(InputStream stream, Rectangle rect)
            throws IOException {
        ImageInputStream imageStream = ImageIO.createImageInputStream(stream);
        ImageReader reader = ImageIO.getImageReaders(imageStream).next();
        ImageReadParam param = reader.getDefaultReadParam();

        param.setSourceRegion(rect);
        reader.setInput(imageStream, true, true);
        BufferedImage image = reader.read(0, param);

        reader.dispose();
        imageStream.close();

        return image;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                createAndShowUI();
            }
        });
    }
}

The result looks like this:

回答2:

Generally, you'd need to do something like this:

Break the image into manageable size image files and store them on disk with your application.
When displaying a particular part of this image, only the load and display image fragments that overlap your viewport.
As you pan around the image, update the loaded and displayed image fragments appropriately.
Either let the unnecessary image fragments get collected by the GC or load new ones in such a way that they overwrite older ones. (This last argues for identically-sized image fragments that load into pooled memory buffers.)

来源：https://stackoverflow.com/questions/15141539/how-do-i-load-an-enormous-image-to-java-via-bufferedimage

标签

java

image

image-processing

java-2d