您必须使用JPEGImageWriteParam，然后使用ImageWriter.write() 保存图像。写之前，通过ImageWriter.setOutput设置输出。
设置压缩级别如下：
JPEGImageWriteParam jpegParams = new JPEGImageWriteParam(null);
jpegParams.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
jpegParams.setCompressionQuality(1f);
1f 是一个浮点数，代表 100% 质量。如果我没记错的话，默认值是大约 70%。
编辑
然后，您必须执行以下操作才能获取ImageWriter 的实例。有两种方法，一种是短的，一种是长的（我都保留了，以防万一）。
捷径（由lapo在一条评论中建议）是：
final ImageWriter writer = ImageIO.getImageWritersByFormatName("jpg").next();
// specifies where the jpg image has to be written
writer.setOutput(new FileImageOutputStream(
new File(folder.toString() + "/" + filename + ".jpg")));
// writes the file with given compression level
// from your JPEGImageWriteParam instance
writer.write(null, new IIOImage(capture, null, null), jpegParams);
或更长的路
// use IIORegistry to get the available services
IIORegistry registry = IIORegistry.getDefaultInstance();
// return an iterator for the available ImageWriterSpi for jpeg images
Iterator<ImageWriterSpi> services = registry.getServiceProviders(ImageWriterSpi.class,
new ServiceRegistry.Filter() {
@Override
public boolean filter(Object provider) {
if (!(provider instanceof ImageWriterSpi)) return false;
ImageWriterSpi writerSPI = (ImageWriterSpi) provider;
String[] formatNames = writerSPI.getFormatNames();
for (int i = 0; i < formatNames.length; i++) {
if (formatNames[i].equalsIgnoreCase("JPEG")) {
return true;
}
}
return false;
}
},
true);
//...assuming that servies.hasNext() == true, I get the first available service.
ImageWriterSpi writerSpi = services.next();
ImageWriter writer = writerSpi.createWriterInstance();
// specifies where the jpg image has to be written
writer.setOutput(new FileImageOutputStream(
new File(folder.toString() + "/" + filename + ".jpg")));
// writes the file with given compression level
// from your JPEGImageWriteParam instance
writer.write(null, new IIOImage(capture, null, null), jpegParams);