java.awt.Graphics2D 图片缩放

import java.awt.Graphics2D;
import java.awt.GraphicsConfiguration;
import java.awt.GraphicsDevice;
import java.awt.GraphicsEnvironment;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.junit.Test;

public class ImageUtils {

@Test
public void test1() throws IOException {
File file = new File("E:\\1.png");

ImageUtils.scale(file, 0.1, new File("E:\\2.jpg"));
ImageUtils.thumbnail(file, 100, new File("E:\\3.jpg"));
}

/**
* 按比例缩放
*
* @param rawImage
* @param ratio
* @param saltImage
*
* @throws IOException
* */
public static void scale(File rawImage, double ratio, File saltImage) throws IOException {
BufferedImage rawBufferedImage = ImageIO.read(rawImage);
int width = (int) (rawBufferedImage.getWidth() * ratio);
int height = (int) (rawBufferedImage.getHeight() * ratio);
BufferedImage bi = getCompatibleImage(width, height);
Graphics2D g2d = bi.createGraphics();
double xScale = (double) width / rawBufferedImage.getWidth();
double yScale = (double) height / rawBufferedImage.getHeight();
AffineTransform at = AffineTransform.getScaleInstance(xScale, yScale);
g2d.drawRenderedImage(rawBufferedImage, at);
g2d.dispose();
ImageIO.write(bi, "jpg", saltImage);
}

/**
* 按比例缩放至【最大边 = 指定pix】
*
* @param rawImage
* @param pixel
* @param saltImage
*
* @throws IOException
* */
public static void thumbnail(File rawImage, int pixel, File saltImage) throws IOException {
BufferedImage source = ImageIO.read(rawImage);
int width = source.getWidth();
int height = source.getHeight();

int l = width > height ? width : height;

double ratio = (pixel * 1.0) / l;

int w = (int) (width * ratio);
int h = (int) (height * ratio);

BufferedImage bi = getCompatibleImage(w, h);
Graphics2D g2d = bi.createGraphics();
double xScale = (double) w / width;
double yScale = (double) h / height;
AffineTransform at = AffineTransform.getScaleInstance(xScale, yScale);
g2d.drawRenderedImage(source, at);
g2d.dispose();
ImageIO.write(bi, "jpg", saltImage);
}

private static BufferedImage getCompatibleImage(int w, int h) {
GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
GraphicsDevice gd = ge.getDefaultScreenDevice();
GraphicsConfiguration gc = gd.getDefaultConfiguration();
BufferedImage image = gc.createCompatibleImage(w, h);
return image;
}

}