thumbnailator 是一个好用的图像处理工具集，可以用来处理缩略图，功能全面，使用简单，目前的版本是 0.4.6 。今天搜索了下开源中国，竟然没收录这个工具（保留原文，此作备注：此处弄错了，OSC中收录了此工具并介绍），特推荐下。有需要的可以从这里下载：http://code.google.com/p/thumbnailator/，maven下也可以使用。有了这么好用的工具，就不用我们再去造轮子了。

先摘几段网站原文API 测试，很简单，一看就懂。

解释其中几个：

size(160, 160)  图像的尺寸，宽，高

rotate（90）旋转90度

watermark（）加水印，在其中可以指定水印的大小和水印图

scale（）缩放比例，scale（1.0f）为不缩放

sourceRegion（int x,int ,y,int width,int height）在某位置切割图片

Create a thumbnail from an image file

Thumbnails.of(new File("original.jpg")).size(160, 160).toFile(new File("thumbnail.jpg"));

In this example, the image from original.jpg is resized, and then saved to thumbnail.jpg.

Alternatively, Thumbnailator will accept file names as a String. Using File objects to specify image files is not required:

Thumbnails.of("original.jpg").size(160, 160.toFile("thumbnail.jpg");

This form can be useful when writing quick prototype code, or when Thumbnailator is being used from scripting languages.

Create a thumbnail with rotation and a watermark

Thumbnails.of(new File("original.jpg")).size(160, 160) .rotate(90).watermark(Positions.BOTTOM_RIGHT, ImageIO.read(new File("watermark.png")), 0.5f) .outputQuality(0.8f).toFile(new File("image-with-watermark.jpg"));

In this example, the image from original.jpg is resized, then rotated to clockwise by 90 degrees, then a watermark is placed at the bottom right-hand corner which is half transparent, then is saved to image-with-watermark.jpg with 80% compression quality settings.

Create a thumbnail and write to an OutputStream

OutputStream os = ...; Thumbnails.of("large-picture.jpg").size(200, 200).outputFormat("png").toOutputStream(os);

In this example, an image from the file large-picture.jpg is resized to a maximum dimension of 200 x 200 (maintaining the aspect ratio of the original image) and writes the that to the specified OutputStream as a PNG image.

Creating fixed-size thumbnails

BufferedImage originalImage = ImageIO.read(new File("original.png")); BufferedImage thumbnail = Thumbnails.of(originalImage).size(200, 200).asBufferedImage();

The above code takes an image in originalImage and creates a 200 pixel by 200 pixel thumbnail using and stores the result in thumbnail.

Scaling an image by a given factor

BufferedImage originalImage = ImageIO.read(new File("original.png")); BufferedImage thumbnail = Thumbnails.of(originalImage).scale(0.25f).asBufferedImage();

The above code takes the image in originalImage and creates a thumbnail that is 25% of the original image, and uses the default scaling technique in order to make the thumbnail which is stored in thumbnail.

Rotating an image when creating a thumbnail

BufferedImage originalImage = ImageIO.read(new File("original.jpg")); BufferedImage thumbnail = Thumbnails.of(originalImage) .size(200, 200).rotate(90).asBufferedImage();

The above code takes the original image and creates a thumbnail which is rotated clockwise by 90 degrees.

Creating a thumbnail with a watermark

BufferedImage originalImage = ImageIO.read(new File("original.jpg")); BufferedImage watermarkImage = ImageIO.read(new File("watermark.png")); BufferedImage thumbnail = Thumbnails.of(originalImage).size(200, 200). watermark(Positions.BOTTOM_RIGHT, watermarkImage, 0.5f) .asBufferedImage();

As shown, a watermark can be added to an thumbnail by calling the watermark method.