利用Thumbnailator轻松实现图片缩放、旋转与加水印

Thumbnails.of(new File("path/to/directory").listFiles())
 .size(640, 480)
 .outputFormat("jpg")
 .toFiles(Rename.PREFIX_DOT_THUMBNAIL);

// 可变长度参数列表
public static Builder<File> of(String... files) {...}
public static Builder<File> of(File... files) {...}
public static Builder<URL> of(URL... urls) {...}
public static Builder<? extends InputStream> of(InputStream... inputStreams) {...}
public static Builder<BufferedImage> of(BufferedImage... images) {...}
// 迭代器（所有实现 Iterable 接口的 Java 对象都可以，当然也包括 List、Set）
public static Builder<File> fromFilenames(Iterable<String> files) {...}
public static Builder<File> fromFiles(Iterable<File> files) {...}
public static Builder<URL> fromURLs(Iterable<URL> urls) {...}
public static Builder<InputStream> fromInputStreams(Iterable<? extends InputStream> inputStreams) {...}
public static Builder<BufferedImage> fromImages(Iterable<BufferedImage> images) {...}

public Builder<T> size(int width, int height)
{
 updateStatus(Properties.SIZE, Status.ALREADY_SET);
 updateStatus(Properties.SCALE, Status.CANNOT_SET);
 
 validateDimensions(width, height);
 this.width = width;
 this.height = height;
 
 return this;
}

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

// 返回图片缓存
public List<BufferedImage> asBufferedImages() throws IOException {...}
public BufferedImage asBufferedImage() throws IOException {...}
// 返回文件列表
public List<File> asFiles(Iterable<File> iterable) throws IOException {...}
public List<File> asFiles(Rename rename) throws IOException {...}
public List<File> asFiles(File destinationDir, Rename rename) throws IOException {...}
// 创建文件
public void toFile(File outFile) throws IOException {...}
public void toFile(String outFilepath) throws IOException {...}
public void toFiles(Iterable<File> iterable) throws IOException {...}
public void toFiles(Rename rename) throws IOException {...}
public void toFiles(File destinationDir, Rename rename) throws IOException {...}
// 创建输出流
public void toOutputStream(OutputStream os) throws IOException {...}
public void toOutputStreams(Iterable<? extends OutputStream> iterable) throws IOException {...}

<dependency>
 <groupId>net.coobird</groupId>
 <artifactId>thumbnailator</artifactId>
 <version>[0.4, 0.5)</version>
</dependency>

Thumbnails.of("oldFile.png")
 .size(16, 16)
 .toFile("newFile_16_16.png");

Thumbnails.of("oldFile.png")
 .scale(2.0)
 .toFile("newFile_scale_2.0.png");

Thumbnails.of("oldFile.png")
 .scale(1.0, 0.5)
 .toFile("newFile_scale_1.0_0.5.png");

Thumbnails.of("oldFile.png")
 .scale(0.8)
 .rotate(90)
 .toFile("newFile_rotate_90.png");

Thumbnails.of("oldFile.png")
 .scale(0.8)
 .rotate(180)
 .toFile("newFile_rotate_180.png");

BufferedImage watermarkImage = ImageIO.read(new File("wartermarkFile.png"));
Thumbnails.of("oldFile.png")
 .scale(0.8)
 .watermark(Positions.BOTTOM_LEFT, watermarkImage, 0.5f)
 .toFile("newFile_watermark.png");

BufferedImage watermarkImage = ImageIO.read(new File("wartermarkFile.png"));

File destinationDir = new File("D:\\watermark\\");
Thumbnails.of("oldFile.png", "oldFile2.png")
 .scale(0.8)
 .watermark(Positions.BOTTOM_LEFT, watermarkImage, 0.5f)
 .toFiles(destinationDir, Rename.PREFIX_DOT_THUMBNAIL);