java url图片压缩

Java 中压缩图片可以使用 ImageIO 类，具体步骤如下：

1. 通过 URL 获取图片输入流

URL url = new URL("http://example.com/image.jpg");
InputStream inputStream = url.openStream();

2. 使用 ImageIO 读取图片

BufferedImage image = ImageIO.read(inputStream);

3. 创建压缩后的图片缓冲区

int width = image.getWidth();
int height = image.getHeight();
BufferedImage compressedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

4. 获取压缩后的图像输出流

OutputStream outputStream = new FileOutputStream("compressed_image.jpg");

5. 创建 JPEGImageEncoder 对象

JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(outputStream);

6. 设置压缩参数

JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(compressedImage);
param.setQuality(0.5f, false); // 压缩质量为 50%

7. 压缩图片并输出

encoder.setJPEGEncodeParam(param);
encoder.encode(compressedImage);

完整代码如下：

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGEncodeParam;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URL;

public class ImageCompressor {
    public static void main(String[] args) throws Exception {
        URL url = new URL("http://example.com/image.jpg");
        InputStream inputStream = url.openStream();
        BufferedImage image = ImageIO.read(inputStream);

        int width = image.getWidth();
        int height = image.getHeight();
        BufferedImage compressedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        OutputStream outputStream = new FileOutputStream("compressed_image.jpg");
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(outputStream);

        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(compressedImage);
        param.setQuality(0.5f, false);

        encoder.setJPEGEncodeParam(param);
        encoder.encode(compressedImage);
    }
}