Java实现对图像文件的压缩

Java提供了多种压缩图像文件的方式，其中常用的包括JPEG和PNG压缩。

使用JPEG压缩：

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

public class ImageCompressor {

    public static void main(String[] args) throws IOException {
        File originalFile = new File("original.jpg");
        BufferedImage originalImage = ImageIO.read(originalFile);

        File compressedFile = new File("compressed.jpg");
        ImageIO.write(originalImage, "jpg", compressedFile);
    }
}

使用PNG压缩：

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Iterator;

public class ImageCompressor {

    public static void main(String[] args) throws IOException {
        File originalFile = new File("original.png");
        BufferedImage originalImage = ImageIO.read(originalFile);

        File compressedFile = new File("compressed.png");

        // Get the iterator for png writers
        Iterator<ImageWriter> writers = ImageIO.getImageWritersByFormatName("png");
        if (!writers.hasNext()) {
            throw new IllegalStateException("No writers found");
        }

        ImageWriter writer = writers.next();
        ImageWriteParam param = writer.getDefaultWriteParam();
        param.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
        param.setCompressionQuality(0.5f); // Set the compression quality between 0 and 1

        FileImageOutputStream output = new FileImageOutputStream(compressedFile);
        writer.setOutput(output);
        writer.write(null, new IIOImage(originalImage, null, null), param);
        output.close();
    }
}

其中，对于JPEG压缩，可以直接使用ImageIO.write()方法，指定输出文件格式为"jpg"即可；对于PNG压缩，需要使用ImageWriter并指定压缩参数，其中可以通过setCompressionQuality()方法设置压缩质量，值为0到1之间的float类型。