java高质量缩放图片的示例代码

可按照比例缩放，也可以指定宽高

import com.sun.image.codec.jpeg.JPEGImageEncoder;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGEncodeParam;
import javax.swing.*;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.Kernel;
import java.awt.image.ConvolveOp;
 
public class ImageUtil {
   

	public static void resize(File originalFile, File resizedFile,
			int newWidth, float quality) throws IOException {
 
		if (quality > 1) {
			throw new IllegalArgumentException(
					"Quality has to be between 0 and 1");
		}
 
		ImageIcon ii = new ImageIcon(originalFile.getCanonicalPath());
		Image i = ii.getImage();
		Image resizedImage = null;
 
		int iWidth = i.getWidth(null);
		int iHeight = i.getHeight(null);
 //比例缩放
		if (iWidth > iHeight) {
			resizedImage = i.getScaledInstance(newWidth, (newWidth * iHeight)
					/ iWidth, Image.SCALE_SMOOTH);
		} else {
			resizedImage = i.getScaledInstance((newWidth * iWidth) / iHeight,
					newWidth, Image.SCALE_SMOOTH);
		}
 //指定宽高
		Image temp = new ImageIcon(resizedImage).getImage();
		// Create the buffered image.
 BufferedImage bufferedImage = new BufferedImage(temp.getWidth(null),
				temp.getHeight(null), BufferedImage.TYPE_INT_RGB);
		// Copy image to buffered image.
 Graphics g = bufferedImage.createGraphics();
		// Clear background and paint the image.
		g.setColor(Color.white);
		g.fillRect(0, 0, temp.getWidth(null), temp.getHeight(null));
		g.drawImage(temp, 0, 0, null);
		g.dispose();
 
		// Soften.
		float softenFactor = 0.05f;
		float[] softenArray = { 0, softenFactor, 0, softenFactor,
				1 - (softenFactor * 4), softenFactor, 0, softenFactor, 0 };
		Kernel kernel = new Kernel(3, 3, softenArray);
		ConvolveOp cOp = new ConvolveOp(kernel, ConvolveOp.EDGE_NO_OP, null);
		bufferedImage = cOp.filter(bufferedImage, null);
 
		// Write the jpeg to a file.
		FileOutputStream out = new FileOutputStream(resizedFile);
 
		// Encodes image as a JPEG data stream
		JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);
 
		JPEGEncodeParam param = encoder
				.getDefaultJPEGEncodeParam(bufferedImage);
 
		param.setQuality(quality, true);
 
		encoder.setJPEGEncodeParam(param);
		encoder.encode(bufferedImage);
	} // Example usage
 
	public static void main(String[] args) throws IOException {
		 File originalImage = new File("C:P7.gif");
		 resize(originalImage, new File("c:P7-0.jpg"),150, 0.7f);
		 resize(originalImage, new File("c:P7-1.jpg"),150, 1f);
	}
}

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