本文目录导读：
我来提供几个Java实现图片缩放的常用方法案例。
基本图片缩放（Java标准库）
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
public class ImageScaler {
/**
* 缩放图片到指定尺寸
* @param sourcePath 源图片路径
* @param targetPath 目标图片路径
* @param width 目标宽度
* @param height 目标高度
*/
public static void scaleImage(String sourcePath, String targetPath,
int width, int height) throws IOException {
// 读取源图片
File sourceFile = new File(sourcePath);
BufferedImage sourceImage = ImageIO.read(sourceFile);
// 创建缩放后的图片
BufferedImage scaledImage = new BufferedImage(width, height,
BufferedImage.TYPE_INT_RGB);
// 绘制缩放后的图片
Graphics2D g2d = scaledImage.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
g2d.drawImage(sourceImage, 0, 0, width, height, null);
g2d.dispose();
// 保存图片
ImageIO.write(scaledImage, "jpg", new File(targetPath));
}
/**
* 等比缩放图片（按比例）
* @param sourcePath 源图片路径
* @param targetPath 目标图片路径
* @param targetWidth 目标宽度（高度会自动计算）
*/
public static void scaleImageByWidth(String sourcePath, String targetPath,
int targetWidth) throws IOException {
File sourceFile = new File(sourcePath);
BufferedImage sourceImage = ImageIO.read(sourceFile);
// 计算等比高度
int originalWidth = sourceImage.getWidth();
int originalHeight = sourceImage.getHeight();
double scale = (double) targetWidth / originalWidth;
int targetHeight = (int) (originalHeight * scale);
scaleImage(sourcePath, targetPath, targetWidth, targetHeight);
}
/**
* 按百分比缩放
* @param sourcePath 源图片路径
* @param targetPath 目标图片路径
* @param percent 缩放百分比（如0.5表示50%）
*/
public static void scaleImageByPercent(String sourcePath, String targetPath,
double percent) throws IOException {
File sourceFile = new File(sourcePath);
BufferedImage sourceImage = ImageIO.read(sourceFile);
int targetWidth = (int) (sourceImage.getWidth() * percent);
int targetHeight = (int) (sourceImage.getHeight() * percent);
scaleImage(sourcePath, targetPath, targetWidth, targetHeight);
}
public static void main(String[] args) {
try {
// 示例1：缩放为固定尺寸
scaleImage("input.jpg", "output_fixed.jpg", 300, 200);
// 示例2：按宽度等比缩放
scaleImageByWidth("input.jpg", "output_width.jpg", 400);
// 示例3：按百分比缩放（缩小50%）
scaleImageByPercent("input.jpg", "output_percent.jpg", 0.5);
System.out.println("图片缩放完成！");
} catch (IOException e) {
e.printStackTrace();
}
}
}
使用Thumbnailator库（推荐）
import net.coobird.thumbnailator.Thumbnails;
import java.io.IOException;
public class ThumbnailatorExample {
/**
* 基本缩放
*/
public static void basicScale() throws IOException {
// 缩放为指定尺寸
Thumbnails.of("input.jpg")
.size(200, 200)
.toFile("output_basic.jpg");
// 按比例缩放
Thumbnails.of("input.jpg")
.scale(0.5) // 缩小50%
.toFile("output_scale.jpg");
}
/**
* 缩放并保持长宽比
*/
public static void scaleWithAspectRatio() throws IOException {
// 按比例缩放，保持长宽比
Thumbnails.of("input.jpg")
.width(300) // 只设置宽度，高度自动计算
.keepAspectRatio(true)
.toFile("output_width.jpg");
Thumbnails.of("input.jpg")
.height(200) // 只设置高度，宽度自动计算
.keepAspectRatio(true)
.toFile("output_height.jpg");
}
/**
* 带旋转的缩放
*/
public static void scaleWithRotation() throws IOException {
Thumbnails.of("input.jpg")
.size(300, 300)
.rotate(90) // 旋转90度
.toFile("output_rotated.jpg");
}
/**
* 缩放并添加水印
*/
public static void scaleWithWatermark() throws IOException {
Thumbnails.of("input.jpg")
.size(500, 500)
.watermark(Thumbnails.of("watermark.png")
.size(100, 100)
.asBufferedImage(), 0.5f) // 半透明水印
.toFile("output_watermark.jpg");
}
public static void main(String[] args) {
try {
basicScale();
scaleWithAspectRatio();
System.out.println("Thumbnailator缩放完成！");
} catch (IOException e) {
e.printStackTrace();
}
}
}
使用ImageMagick（通过JMagick）
import magick.ImageInfo;
import magick.MagickImage;
import magick.MagickException;
public class JMagickExample {
/**
* 使用ImageMagick缩放图片
*/
public static void scaleWithImageMagick(String sourcePath, String targetPath,
int width, int height) {
try {
ImageInfo imageInfo = new ImageInfo(sourcePath);
MagickImage image = new MagickImage(imageInfo);
// 缩放图片
MagickImage scaledImage = image.scaleImage(width, height);
// 保存图片
scaledImage.setFileName(targetPath);
scaledImage.writeImage(new ImageInfo());
System.out.println("ImageMagick缩放完成！");
} catch (MagickException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
scaleWithImageMagick("input.jpg", "output_magick.jpg", 300, 200);
}
}
批量图片缩放工具
import javax.imageio.ImageIO;
import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class BatchImageScaler {
private static class ScalingTask implements Runnable {
private File sourceFile;
private File targetDir;
private int maxWidth;
private int maxHeight;
public ScalingTask(File sourceFile, File targetDir, int maxWidth, int maxHeight) {
this.sourceFile = sourceFile;
this.targetDir = targetDir;
this.maxWidth = maxWidth;
this.maxHeight = maxHeight;
}
@Override
public void run() {
try {
BufferedImage sourceImage = ImageIO.read(sourceFile);
if (sourceImage == null) {
System.out.println("无法读取图片: " + sourceFile.getName());
return;
}
// 计算缩放比例
int originalWidth = sourceImage.getWidth();
int originalHeight = sourceImage.getHeight();
double scale = Math.min(
(double) maxWidth / originalWidth,
(double) maxHeight / originalHeight
);
if (scale >= 1.0) {
// 原图小于目标尺寸，直接复制
File targetFile = new File(targetDir, sourceFile.getName());
ImageIO.write(sourceImage, getExtension(sourceFile.getName()), targetFile);
return;
}
int targetWidth = (int) (originalWidth * scale);
int targetHeight = (int) (originalHeight * scale);
// 缩放图片
BufferedImage scaledImage = new BufferedImage(targetWidth, targetHeight,
BufferedImage.TYPE_INT_RGB);
Graphics2D g2d = scaledImage.createGraphics();
g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
RenderingHints.VALUE_INTERPOLATION_BILINEAR);
g2d.drawImage(sourceImage, 0, 0, targetWidth, targetHeight, null);
g2d.dispose();
// 保存图片
File targetFile = new File(targetDir, sourceFile.getName());
ImageIO.write(scaledImage, "jpg", targetFile);
System.out.println("已缩放: " + sourceFile.getName() +
" (" + originalWidth + "x" + originalHeight +
" → " + targetWidth + "x" + targetHeight + ")");
} catch (IOException e) {
System.err.println("处理失败: " + sourceFile.getName());
e.printStackTrace();
}
}
private String getExtension(String fileName) {
int lastDot = fileName.lastIndexOf('.');
return lastDot > 0 ? fileName.substring(lastDot + 1).toLowerCase() : "jpg";
}
}
/**
* 批量缩放图片
*/
public static void batchScale(String sourceDirPath, String targetDirPath,
int maxWidth, int maxHeight) {
File sourceDir = new File(sourceDirPath);
File targetDir = new File(targetDirPath);
if (!sourceDir.exists() || !sourceDir.isDirectory()) {
System.err.println("源目录不存在: " + sourceDirPath);
return;
}
if (!targetDir.exists()) {
targetDir.mkdirs();
}
// 获取所有图片文件
File[] imageFiles = sourceDir.listFiles((dir, name) -> {
String lowerName = name.toLowerCase();
return lowerName.endsWith(".jpg") ||
lowerName.endsWith(".jpeg") ||
lowerName.endsWith(".png") ||
lowerName.endsWith(".bmp");
});
if (imageFiles == null || imageFiles.length == 0) {
System.out.println("没有找到图片文件");
return;
}
System.out.println("开始批量缩放 " + imageFiles.length + " 个图片...");
// 使用线程池处理
ExecutorService executor = Executors.newFixedThreadPool(
Runtime.getRuntime().availableProcessors()
);
for (File imageFile : imageFiles) {
executor.submit(new ScalingTask(imageFile, targetDir, maxWidth, maxHeight));
}
executor.shutdown();
while (!executor.isTerminated()) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}
}
System.out.println("批量缩放完成！");
}
public static void main(String[] args) {
batchScale("source_images", "scaled_images", 800, 600);
}
}
Maven依赖配置
如果使用Thumbnailator库,需要在pom.xml中添加：
<dependency>
<groupId>net.coobird</groupId>
<artifactId>thumbnailator</artifactId>
<version>0.4.20</version>
</dependency>
这些示例涵盖了Java中常见的图片缩放场景,可以根据具体需求选择合适的方法。
