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 following popular product: thumbnailator

Answer 2

After loading the image you can try:

BufferedImage createResizedCopy(Image originalImage, 
            int scaledWidth, int scaledHeight, 
            boolean preserveAlpha)
    {
        System.out.println("resizing...");
        int imageType = preserveAlpha ? BufferedImage.TYPE_INT_RGB : BufferedImage.TYPE_INT_ARGB;
        BufferedImage scaledBI = new BufferedImage(scaledWidth, scaledHeight, imageType);
        Graphics2D g = scaledBI.createGraphics();
        if (preserveAlpha) {
            g.setComposite(AlphaComposite.Src);
        }
        g.drawImage(originalImage, 0, 0, scaledWidth, scaledHeight, null); 
        g.dispose();
        return scaledBI;
    }

Answer 3

Thumbnailator is an open-source image resizing library for Java with a fluent interface, distributed under the MIT license.

I wrote this library because making high-quality thumbnails in Java can be surprisingly difficult, and the resulting code could be pretty messy. With Thumbnailator, it's possible to express fairly complicated tasks using a simple fluent API.

A simple example

For a simple example, taking a image and resizing it to 100 x 100 (preserving the aspect ratio of the original image), and saving it to an file can achieved in a single statement:

Thumbnails.of("path/to/image")
    .size(100, 100)
    .toFile("path/to/thumbnail");

An advanced example

Performing complex resizing tasks is simplified with Thumbnailator's fluent interface.

Let's suppose we want to do the following:

1. take the images in a directory and,
2. resize them to 100 x 100, with the aspect ratio of the original image,
3. save them all to JPEGs with quality settings of 0.85,
4. where the file names are taken from the original with thumbnail. appended to the beginning

Translated to Thumbnailator, we'd be able to perform the above with the following:

Thumbnails.of(new File("path/to/directory").listFiles())
    .size(100, 100)
    .outputFormat("JPEG")
    .outputQuality(0.85)
    .toFiles(Rename.PREFIX_DOT_THUMBNAIL);

A note about image quality and speed

This library also uses the progressive bilinear scaling method highlighted in Filthy Rich Clients by Chet Haase and Romain Guy in order to generate high-quality thumbnails while ensuring acceptable runtime performance.

Answer 4

I have developed a solution with the freely available classes ( AnimatedGifEncoder, GifDecoder, and LWZEncoder) available for handling GIF Animation.
You can download the jgifcode jar and run the GifImageUtil class. Link: http://www.jgifcode.com