How can I resize an image using Java?

Question

I need to resize PNG, JPEG and GIF files. How can I do this using Java?

Answer 1

You can use Marvin (pure Java image processing framework) for this kind of operation: http://marvinproject.sourceforge.net

Scale plug-in: http://marvinproject.sourceforge.net/en/plugins/scale.html

Answer 2

If you dont want to import imgScalr like @Riyad Kalla answer above which i tested too works fine, you can do this taken from Peter Walser answer @Peter Walser on another issue though:

 /**
     * utility method to get an icon from the resources of this class
     * @param name the name of the icon
     * @return the icon, or null if the icon wasn't found.
     */
    public Icon getIcon(String name) {
        Icon icon = null;
        URL url = null;
        ImageIcon imgicon = null;
        BufferedImage scaledImage = null;
        try {
            url = getClass().getResource(name);

            icon = new ImageIcon(url);
            if (icon == null) {
                System.out.println("Couldn't find " + url);
            }

            BufferedImage bi = new BufferedImage(
                    icon.getIconWidth(),
                    icon.getIconHeight(),
                    BufferedImage.TYPE_INT_RGB);
            Graphics g = bi.createGraphics();
            // paint the Icon to the BufferedImage.
            icon.paintIcon(null, g, 0,0);
            g.dispose();

            bi = resizeImage(bi,30,30);
            scaledImage = bi;// or replace with this line Scalr.resize(bi, 30,30);
            imgicon = new ImageIcon(scaledImage);

        } catch (Exception e) {
            System.out.println("Couldn't find " + getClass().getName() + "/" + name);
            e.printStackTrace();
        }
        return imgicon;
    }

 public static BufferedImage resizeImage (BufferedImage image, int areaWidth, int areaHeight) {
        float scaleX = (float) areaWidth / image.getWidth();
        float scaleY = (float) areaHeight / image.getHeight();
        float scale = Math.min(scaleX, scaleY);
        int w = Math.round(image.getWidth() * scale);
        int h = Math.round(image.getHeight() * scale);

        int type = image.getTransparency() == Transparency.OPAQUE ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;

        boolean scaleDown = scale < 1;

        if (scaleDown) {
            // multi-pass bilinear div 2
            int currentW = image.getWidth();
            int currentH = image.getHeight();
            BufferedImage resized = image;
            while (currentW > w || currentH > h) {
                currentW = Math.max(w, currentW / 2);
                currentH = Math.max(h, currentH / 2);

                BufferedImage temp = new BufferedImage(currentW, currentH, type);
                Graphics2D g2 = temp.createGraphics();
                g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
                g2.drawImage(resized, 0, 0, currentW, currentH, null);
                g2.dispose();
                resized = temp;
            }
            return resized;
        } else {
            Object hint = scale > 2 ? RenderingHints.VALUE_INTERPOLATION_BICUBIC : RenderingHints.VALUE_INTERPOLATION_BILINEAR;

            BufferedImage resized = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2 = resized.createGraphics();
            g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, hint);
            g2.drawImage(image, 0, 0, w, h, null);
            g2.dispose();
            return resized;
        }
    }

Answer 3

Image Magick has been mentioned. There is a JNI front end project called JMagick. It's not a particularly stable project (and Image Magick itself has been known to change a lot and even break compatibility). That said, we've had good experience using JMagick and a compatible version of Image Magick in a production environment to perform scaling at a high throughput, low latency rate. Speed was substantially better then with an all Java graphics library that we previously tried.

http://www.jmagick.org/index.html

Answer 4

If you are dealing with large images or want a nice looking result it's not a trivial task in java. Simply doing it via a rescale op via Graphics2D will not create a high quality thumbnail. You can do it using JAI, but it requires more work than you would imagine to get something that looks good and JAI has a nasty habit of blowing our your JVM with OutOfMemory errors.

I suggest using ImageMagick as an external executable if you can get away with it. Its simple to use and it does the job right so that you don't have to.

Answer 5

FWIW I just released (Apache 2, hosted on GitHub) a simple image-scaling library for Java called imgscalr (available on Maven central).

The library implements a few different approaches to image-scaling (including Chris Campbell's incremental approach with a few minor enhancements) and will either pick the most optimal approach for you if you ask it to, or give you the fastest or best looking (if you ask for that).

Usage is dead-simple, just a bunch of static methods. The simplest use-case is:

BufferedImage scaledImage = Scalr.resize(myImage, 200);

All operations maintain the image's original proportions, so in this case you are asking imgscalr to resize your image within a bounds of 200 pixels wide and 200 pixels tall and by default it will automatically select the best-looking and fastest approach for that since it wasn't specified.

I realize on the outset this looks like self-promotion (it is), but I spent my fair share of time googling this exact same subject and kept coming up with different results/approaches/thoughts/suggestions and decided to sit down and write a simple implementation that would address that 80-85% use-cases where you have an image and probably want a thumbnail for it -- either as fast as possible or as good-looking as possible (for those that have tried, you'll notice doing a Graphics.drawImage even with BICUBIC interpolation to a small enough image, it still looks like garbage).

Answer 6

The Java API does not provide a standard scaling feature for images and downgrading image quality.

Because of this I tried to use cvResize from JavaCV but it seems to cause problems.

I found a good library for image scaling: simply add the dependency for "java-image-scaling" in your pom.xml.

<dependency>
    <groupId>com.mortennobel</groupId>
    <artifactId>java-image-scaling</artifactId>
    <version>0.8.6</version>
</dependency>

In the maven repository you will get the recent version for this.

Ex. In your java program

ResampleOp resamOp = new ResampleOp(50, 40);
BufferedImage modifiedImage = resamOp.filter(originalBufferedImage, null);