Java调整图片大小的两种方式

1：使用Thumbnailator

Thumbnailator是Java的开源图像大小调整库，它使用渐进式双线性缩放。它支持JPG，BMP，JPEG，WBMP，PNG和GIF。

通过将以下Maven依赖项添加到我们的pom.xml中，将其包括在我们的项目中：

pom.xml

<dependency>
    <groupId>net.coobird</groupId>
    <artifactId>thumbnailator</artifactId>
    <version>0.4.11</version>
</dependency>

工具类ThumbnailsUtils

import net.coobird.thumbnailator.Thumbnails;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;

public class ThumbnailsUtils{
    private static final Logger logger = LoggerFactory.getLogger(ThumbnailsUtils.class);

    /**
     * 通过BufferedImage图片流调整图片大小
     */
    public static BufferedImage resizeImageOne(BufferedImage originalImage, int targetWidth, int targetHeight) throws Exception {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        Thumbnails.of(originalImage)
                .size(targetWidth, targetHeight)
                .outputFormat("JPEG")
                .outputQuality(1)
                .toOutputStream(outputStream);
        byte[] data = outputStream.toByteArray();
        ByteArrayInputStream inputStream = new ByteArrayInputStream(data);
        return ImageIO.read(inputStream);
    }
   
    /**
     * BufferedImage图片流转byte[]数组
     */
    public static byte[] imageToBytes(BufferedImage bImage) {
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        try {
            ImageIO.write(bImage, "jpg", out);
        } catch (IOException e) {
            logger.error("错误信息: ", e);
        }
        return out.toByteArray();
    }


    /**
     * byte[]数组转BufferedImage图片流
     */
    private static BufferedImage bytesToBufferedImage(byte[] ImageByte) {
        ByteArrayInputStream in = new ByteArrayInputStream(ImageByte);
        BufferedImage image = null;
        try {
            image = ImageIO.read(in);
        } catch (IOException e) {
            logger.error("错误信息: ", e);
        }
        return image;
    }
}

2：Graphics2D 自带的方法

 public static BufferedImage scaleImage(BufferedImage originalImage, int targetWidth, int targetHeight) {
        int type = originalImage.getType() == 0 ? BufferedImage.TYPE_INT_ARGB : originalImage.getType();
        BufferedImage scaledImage = new BufferedImage(targetWidth, targetHeight, type);
        Graphics2D g = scaledImage.createGraphics();
// Calculate the ratio between the original and scaled image size
        double scaleX = (double) targetWidth / originalImage.getWidth();
        double scaleY = (double) targetHeight / originalImage.getHeight();
        double scale = Math.min(scaleX, scaleY);
// Now we perform the actual scaling
        int newWidth = (int) (originalImage.getWidth() * scale);
        int newHeight = (int) (originalImage.getHeight() * scale);
        int x = (targetWidth - newWidth) / 2;
        int y = (targetHeight - newHeight) / 2;
        g.drawImage(originalImage.getScaledInstance(newWidth, newHeight, Image.SCALE_SMOOTH), x, y, null);
        g.dispose();
        return scaledImage;
    }

 public static void main(String[] args) throws Exception {
    // 读取原始图片
    File originalFile = new File("D:\\test1\\schoolLogo.png");
    BufferedImage originalImage = ImageIO.read(originalFile);

    // 设定目标宽高
    int targetWidth =  1000; // 两倍放大
    int targetHeight = 1000; // 两倍放大

    // 调用 resizeImageOne 方法进行放大
    BufferedImage resizedImage =  ThumbnailsUtils.scaleImage(originalImage, targetWidth, targetHeight);

    // 将放大后的图片保存到文件
    File outputFile = new File("D:\\test1\\big.png");
    ImageIO.write(resizedImage, "png", outputFile);
}