jsp上传图片并产生缩略图的代码

答案：/**
 * 图片缩小算法，方形区域抽样
 */
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;

import javax.imageio.ImageIO;

import org.apache.commons.io.FileUtils;

public class ImageUtil {

	private int width;
	private int height;
	private int zoomWidth;
	private int zoomHeight;
	private File destFile;
	private BufferedImage srcBufferImage;

	public static void resizeFix(File srcFile, File destFile, int width,
			int height) throws IOException {
		new ImageUtil(srcFile, destFile, width, height);
	}

	public static void resizeFix(BufferedImage bufImg, File destFile,
			int width, int height) throws IOException {
		new ImageUtil(bufImg, destFile, width, height);
	}

	protected ImageUtil(File srcFile, File destFile, int zoomWidth,
			int zoomHeight) throws IOException {
		this.destFile = destFile;
		this.zoomWidth = zoomWidth;
		this.zoomHeight = zoomHeight;
		this.srcBufferImage = javax.imageio.ImageIO.read(srcFile);
		this.width = this.srcBufferImage.getWidth();
		this.height = this.srcBufferImage.getHeight();
		if (width <= zoomWidth && height <= zoomHeight) {
			FileUtils.copyFile(srcFile, destFile);
		} else {
			resizeFix();
		}
	}

	protected ImageUtil(BufferedImage srcBufferImage, File destFile,
			int zoomWidth, int zoomHeight) throws IOException {
		this.destFile = destFile;
		this.zoomWidth = zoomWidth;
		this.zoomHeight = zoomHeight;
		this.srcBufferImage = srcBufferImage;
		this.width = this.srcBufferImage.getWidth();
		this.height = this.srcBufferImage.getHeight();
		resizeFix();
	}

	/**
	 * 压缩图片
	 * 
	 * @throws IOException
	 */
	protected void resizeFix() throws IOException {
		if (width <= zoomWidth && height <= zoomHeight) {
			resize(width, height);
		} else if ((float) width / height > (float) zoomWidth / zoomHeight) {
			resize(zoomWidth, Math.round((float) zoomWidth * height / width));
		} else {
			resize(Math.round((float) zoomHeight * width / height), zoomHeight);
		}
	}

	private void resize(int w, int h) throws IOException {
		BufferedImage imgBuf = scaleImage(w, h);
		File parent = destFile.getParentFile();
		if (!parent.exists()) {
			parent.mkdirs();
		}
		ImageIO.write(imgBuf, "jpeg", destFile);
	}

	private BufferedImage scaleImage(int outWidth, int outHeight) {
		int[] rgbArray = srcBufferImage.getRGB(0, 0, width, height, null, 0,
				width);
		BufferedImage pbFinalOut = new BufferedImage(outWidth, outHeight,
				BufferedImage.TYPE_INT_RGB);
		double hScale = ((double) width) / ((double) outWidth);// 宽缩小的倍数
		double vScale = ((double) height) / ((double) outHeight);// 高缩小的倍数

		int winX0, winY0, winX1, winY1;
		int valueRGB = 0;
		long R, G, B;
		int x, y, i, j;
		int n;
		for (y = 0; y < outHeight; y++) {
			winY0 = (int) (y * vScale + 0.5);// 得到原图高的Y坐标
			if (winY0 < 0) {
				winY0 = 0;
			}
			winY1 = (int) (winY0 + vScale + 0.5);
			if (winY1 > height) {
				winY1 = height;
			}
			for (x = 0; x < outWidth; x++) {
				winX0 = (int) (x * hScale + 0.5);
				if (winX0 < 0) {
					winX0 = 0;
				}
				winX1 = (int) (winX0 + hScale + 0.5);
				if (winX1 > width) {
					winX1 = width;
				}
				R = 0;
				G = 0;
				B = 0;
				for (i = winX0; i < winX1; i++) {
					for (j = winY0; j < winY1; j++) {
						valueRGB = rgbArray[width * j + i];
						R += getRedValue(valueRGB);
						G += getGreenValue(valueRGB);
						B += getBlueValue(valueRGB);
					}
				}
				n = (winX1 - winX0) * (winY1 - winY0);
				R = (int) (((double) R) / n + 0.5);
				G = (int) (((double) G) / n + 0.5);
				B = (int) (((double) B) / n + 0.5);
				valueRGB = comRGB(clip((int) R), clip((int) G), clip((int) B));
				pbFinalOut.setRGB(x, y, valueRGB);
			}
		}
		return pbFinalOut;
	}

	private int clip(int x) {
		if (x < 0)
			return 0;
		if (x > 255)
			return 255;
		return x;
	}

	private int getRedValue(int rgbValue) {
		int temp = rgbValue & 0x00ff0000;
		return temp >> 16;
	}

	private int getGreenValue(int rgbValue) {
		int temp = rgbValue & 0x0000ff00;
		return temp >> 8;
	}

	private int getBlueValue(int rgbValue) {
		return rgbValue & 0x000000ff;
	}

	private int comRGB(int redValue, int greenValue, int blueValue) {

		return (redValue << 16) + (greenValue << 8) + blueValue;
	}

	public static void main(String[] args) throws IOException {
		long start = System.currentTimeMillis();
		ImageUtil.resizeFix(new File("d:/04.jpg"), new File("d:/big-n.jpg"),
				400, 400);
		long end = System.currentTimeMillis();
		System.out.println("success:" + (end - start));
	}
}

依赖commons-io.jar

其他：我用的是uploadify

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