方式一：使用Image.getScaledInstance
使用jdk的awt包下的Image.getScaledInstance实现图片的缩放。好处是无需引入第三方jar，缺点是会稍微有点模糊。
工具类ImageUtils：
package utils;
import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
public class ImageUtils {
public static BufferedImage resizeImage(BufferedImage originalImage, int targetWidth, int targetHeight) throws IOException {
Image resultingImage = originalImage.getScaledInstance(targetWidth, targetHeight, Image.SCALE_AREA_AVERAGING);
BufferedImage outputImage = new BufferedImage(targetWidth, targetHeight, BufferedImage.TYPE_INT_RGB);
outputImage.getGraphics().drawImage(resultingImage, 0, 0, null);
return outputImage;
}
public static byte[] imageToBytes(BufferedImage bImage) {
ByteArrayOutputStream out = new ByteArrayOutputStream();
try {
ImageIO.write(bImage, "jpg", out);
} catch (IOException e) {
e.printStackTrace();
}
return out.toByteArray();
}
private static BufferedImage bytesToBufferedImage(byte[] ImageByte) {
ByteArrayInputStream in = new ByteArrayInputStream(ImageByte);
BufferedImage image = null;
try {
image = ImageIO.read(in);
} catch (IOException e) {
e.printStackTrace();
}
return image;
}
}
测试
1.通过 url 获取图片并调整大小后保存：
import utils.ImageUtils;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;
public class Test {
public static void main(String[] args) {
try {
//通过url获取BufferedImage图像缓冲区
URL img = new URL("https://img1.360buyimg.com/image/jfs/t1/38591/20/3737/314695/5cc69c01E1838df09/dd6dce681bd23031.jpg");
BufferedImage image = ImageIO.read(img);
//获取图片的宽、高
System.out.println("Width: " + image.getWidth());
System.out.println("Height: " + image.getHeight());
//调整图片大小为 400X400尺寸
BufferedImage newImage = ImageUtils.resizeImage(image,400,400);
//将缓冲区图片保存到 F:/test/pic1.jpg (文件不存在会自动创建文件保存，文件存在会覆盖原文件保存)
ImageIO.write(newImage, "jpg", new File("F:/test/pic1.jpg"));
} catch (IOException e) {
e.printStackTrace();
}
}
}
2.通过读取图片文件调整大小再保存：
import utils.ImageUtils;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
public class Test {
public static void main(String[] args) {
try {
//读取原始图片
BufferedImage image = ImageIO.read(new FileInputStream("F:/test/pic1.jpg"));
System.out.println("Width: " + image.getWidth());
System.out.println("Height: " + image.getHeight());
//调整图片大小
BufferedImage newImage = ImageUtils.resizeImage(image,200,200);
//图像缓冲区图片保存为图片文件(文件不存在会自动创建文件保存，文件存在会覆盖原文件保存)
ImageIO.write(newImage, "jpg", new File("F:/test/pic2.jpg"));
} catch (IOException e) {
e.printStackTrace();
}
}
}
3.MultipartFile类型的图片文件调整大小再保存：
public JSONObject imageSizeAdjustment(MultipartFile file) {
JSONObject result = new JSONObject();
try {
//从MultipartFile 中获取 byte[]
byte[] bytes = file.getBytes();
//byte[]转 InputStream
InputStream in = new ByteArrayInputStream(bytes);
//读取图片输入流为 BufferedImage
BufferedImage image = ImageIO.read(in);
System.out.println("Width: " + image.getWidth());
System.out.println("Height: " + image.getHeight());
//调整图片大小
BufferedImage newImage = ImageUtils.resizeImage(image, 200, 200);
//图像缓冲区图片保存为图片文件(文件不存在会自动创建文件保存，文件存在会覆盖原文件保存)
ImageIO.write(newImage, "jpg", new File("F:/test/pic2.jpg"));
} catch (IOException e) {
e.printStackTrace();
}
result.put("code", 1);
result.put("note", "成功");
return result;
}
方式二：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：
<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);
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);
}
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();
}
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;
}
}
测试
和上面测试基本一样只不过 ImageUtils.resizeImage换成 ThumbnailsUtils.resizeImageOne即可。
最终效果：
原图：
长宽缩为原来的三分之一后的图：
如果需要将 BufferedImage 转换为 MultipartFile，请参考我另一篇文章：
BufferedImage转换为MultipartFile
其他图片大小调整方法请参考：
How Can I Resize an Image Using Java
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
