贴一个生成缩略图的类

实现图片等比缩放

public class ImageEncoder {   
	public BufferedImage resize(BufferedImage source, int targetW,
			int targetH) {
		// 长和宽
		int type = source.getType();
		BufferedImage target = null;
		double sx = (double) targetW / source.getWidth();
		double sy = (double) targetH / source.getHeight();
		// 等比缩放
		if (sx > sy) {
			sx = sy;
			targetW = (int) (sx * source.getWidth());
		} else {
			sy = sx;
			targetH = (int) (sy * source.getHeight());
		}
		if (type == BufferedImage.TYPE_CUSTOM) { 
			ColorModel cm = source.getColorModel();
			WritableRaster raster = cm.createCompatibleWritableRaster(targetW,targetH);
			boolean alphaPremultiplied = cm.isAlphaPremultiplied();
			target = new BufferedImage(cm, raster, alphaPremultiplied, null);
		} else{
			target = new BufferedImage(targetW, targetH, type);
		}
		Graphics2D g = target.createGraphics();
		// 开始画图
		g.setRenderingHint(RenderingHints.KEY_RENDERING,RenderingHints.VALUE_RENDER_QUALITY);
		g.drawRenderedImage(source, AffineTransform.getScaleInstance(sx, sy));
		g.dispose();
		return target;
	}   
	
	public BufferedImage getBufferedImage(String image,int width,int height){
		try {
			BufferedImage srcImage = ImageIO.read(new File(image));
			if (width > 0 || height > 0) {
				srcImage = resize(srcImage, width, height);
			}
			return srcImage;
		} catch (IOException e) {
			e.printStackTrace();
		}
		return null;
	}
}

Servlet中使用实例：(/ImageProc)

protected void doPost(HttpServletRequest request, HttpServletResponse response) 
		throws ServletException, IOException {
		synchronized (this) {
			String img = request.getParameter("img");
			int width = Integer.parseInt(request.getParameter("width"));
			int height = Integer.parseInt(request.getParameter("height"));
			BufferedImage bi = ie.getBufferedImage(img, width, height);
			ServletOutputStream sos = response.getOutputStream();
			ImageIO.write(bi, "jpg", sos);
		}
	}

JSP页面使用<img/>标签指定src为这个servlet的urlparttern就可以了

<img src="<%=contextPath%>/ImageProc?img=D:/DEMO.jpg&width=160&height=200"/>