压缩剪贴板内图片并立即写入剪贴板，减轻服务器存储压力
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更新日志
- v1.0.1 发现 jdk 内置的压缩效果实在太差，最终引入了
net.coobird的thumbnailator库进行图片的压缩 - v1.0.0 最初版本发布
背景
在使用 self-built chatting system 聊天时，用的是非官方的服务器，有时候从 X 或者 TG 上粘贴一张图片过来，9 MB 的大小让人深感 vps 硬盘不够大，得省着点用。所以我想压缩一下图片再粘贴到聊天框，于是我就寻找一个简单快捷的工作流，但是很遗憾我没有找到。
于是我用 Java 写了一段代码实现了这个逻辑
- 从其他任意地方复制图片（此时系统剪贴板里应是一张图片）
- 执行一条命令，直接将压缩后的图片写入剪贴板（此时剪贴板里是压缩后的图片）
- 直接在聊天页面中粘贴，此时粘贴的是压缩后的图片，达到了我们想要照顾服务器硬盘太小的这个目的
使用效果
我用自建的 Mattermost 举例
压缩前
压缩后
压缩前后对比
源码实现
基于 OpenJDK11 开发和构建，打包成了 jar，全部使用 jdk 内嵌包，没有引入第三方图片压缩的库，按理说可以引入，因为压缩后的成片质量可能比自带的 Graphics2D g = resImage.createGraphics(); g.drawImage(image, 0, 0, newWidth, newHeight, null); 效果好，但我此处的需求很简单，就是聊天时用用，对于图片的清晰度可能要求不是很高，有些文字很多的都快包浆了的那种图片也不适合压缩后再发送。
源码
import net.coobird.thumbnailator.Thumbnails;
import javax.imageio.ImageIO;
import java.awt.Graphics2D;
import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.text.DecimalFormat;
/**
* @author: hellodk
* @description CompressImageAndPaste
* @date: 11/3/2023 1:13 PM
*/
public class CompressImageAndPaste {
/**
* 压缩倍率
*/
private static final double compress_ratio = 0.4;
public static void main(String[] args) {
CompressImageAndPaste ciap = new CompressImageAndPaste();
BufferedImage srcImage = ciap.readImageFromClipboard();
if (srcImage == null) {
return;
}
long sizeInBytes = ciap.getImageSizeInBytes(srcImage);
String sizeInHumanReadable = ciap.formatSize(sizeInBytes);
System.out.println("Original image size is " + sizeInHumanReadable + ".");
BufferedImage compressedImage = ciap.compressImage(srcImage, compress_ratio); // 压缩比例设置为 0.4
ciap.writeImage2Clipboard(compressedImage);
long newSizeInBytes = ciap.getImageSizeInBytes(compressedImage);
String newSizeInHumanReadable = ciap.formatSize(newSizeInBytes);
System.out.print("Compressed image size is " + newSizeInHumanReadable);
System.out.println(", and has been written to your clipboard, you can paste it anywhere.");
}
private BufferedImage readImageFromClipboard() {
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
Transferable transferable = clipboard.getContents(null);
if (transferable != null && transferable.isDataFlavorSupported(DataFlavor.imageFlavor)) {
try {
return (BufferedImage) transferable.getTransferData(DataFlavor.imageFlavor);
}
catch (UnsupportedFlavorException | IOException e) {
e.printStackTrace();
}
}
else {
System.out.println("Make sure your clipboard latest item is image and continue.");
System.out.println("Jar usage description: read your clipboard image and compress it, finally write the compressed image to your clipboard, you can paste it anywhere.");
}
return null;
}
private BufferedImage compressImage(BufferedImage image, double compressRatio) {
BufferedImage resImage = null;
try {
Path tmpFilePath = Files.createTempFile("compressed_image", ".jpg");
File targetFile = tmpFilePath.toFile();
Thumbnails.of(image)
.scale(1)
.outputQuality(compressRatio)
.toFile(targetFile);
resImage = ImageIO.read(targetFile);
}
catch (IOException e) {
e.printStackTrace();
}
return resImage;
}
private void writeImage2Clipboard(BufferedImage image) {
Clipboard cb = Toolkit.getDefaultToolkit().getSystemClipboard();
ImageTransferable it = new ImageTransferable(image);
cb.setContents(it, null);
}
private long getImageSizeInBytes(BufferedImage image) {
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
try {
ImageIO.write(image, "jpg", outputStream);
}
catch (IOException e) {
e.printStackTrace();
}
byte[] compressedImageBytes = outputStream.toByteArray();
long sizeInBytes = compressedImageBytes.length;
return sizeInBytes;
}
private String formatSize(long sizeInBytes) {
String[] units = {"B", "KB", "MB", "GB", "TB"};
int unitIndex = 0;
double size = sizeInBytes;
while (size >= 1024 && unitIndex < units.length - 1) {
size /= 1024;
unitIndex++;
}
DecimalFormat df = new DecimalFormat("#.##");
return df.format(size) + " " + units[unitIndex];
}
// 自定义Transferable类，用于将BufferedImage对象传输到剪贴板
private static class ImageTransferable implements Transferable {
private final BufferedImage image;
public ImageTransferable(BufferedImage image) {
this.image = image;
}
@Override
public DataFlavor[] getTransferDataFlavors() {
return new DataFlavor[]{DataFlavor.imageFlavor};
}
@Override
public boolean isDataFlavorSupported(DataFlavor flavor) {
return flavor.equals(DataFlavor.imageFlavor);
}
@Override
public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
if (flavor.equals(DataFlavor.imageFlavor)) {
return image;
}
else {
throw new UnsupportedFlavorException(flavor);
}
}
}
}
使用方法
发布到了 GitHub: https://github.com/hellodk34/CompressImageAndPaste ，从 release 页面下载 jar 包(最新版本 v1.0.1)。需要在电脑上安装 jdk11 环境，然后直接执行
java -jar compress_image_and_paste.jar即可。
一些执行日志：
java -jar compress_image_and_paste.jar
Make sure your clipboard latest item is image and continue.
Jar usage description: read your clipboard image and compress it, finally write the compressed image to your clipboard, you can paste it anywhere.
java -jar compress_image_and_paste.jar
Original image size is 9.18 MB.
Compressed image size is 1.47 MB, and has been written to your clipboard, you can paste it anywhere.