JSP如何缩放图像？

您可以为此使用内置的Java 2D API（此处是基本的Sun教程）。

基本上，您需要创建一个Servlet，该Servlet获取方法

InputStream

doGet()

OutputStream

url-pattern

web.xml

/thumbs/*

src

<img>

这是一个基本的启动示例（您仍然需要自己以所需的方式处理意外情况）：

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {    // First get image file name as request pathinfo (or parameter, whatever you want).    String imageFilename = request.getPathInfo().substring(1);    // And get the thumbnail dimensions as request parameters as well.    int thumbWidth = Integer.parseInt(request.getParameter("w"));    int thumbHeight = Integer.parseInt(request.getParameter("h"));    // Then get an InputStream of image from for example local disk file system.    InputStream imageInput = new FileInputStream(new File("/images", imageFilename));    // Now scale the image using Java 2D API to the desired thumb size.    Image image = ImageIO.read(imageInput);    BufferedImage thumb = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);    Graphics2D graphics2D = thumb.createGraphics();    graphics2D.setBackground(Color.WHITE);    graphics2D.setPaint(Color.WHITE);     graphics2D.fillRect(0, 0, thumbWidth, thumbHeight);    graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);    graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);    // Write the image as JPG to the response along with correct content type.    response.setContentType("image/jpeg");    ImageIO.write(thumb, "JPG", response.getOutputStream());}

servlet映射

web.xml

<servlet>    <servlet-name>thumbServlet</servlet-name>    <servlet-class>com.example.ThumbServlet</servlet-class></servlet><servlet-mapping>    <servlet-name>thumbServlet</servlet-name>    <url-pattern>/thumbs/*</url-pattern>        </servlet-mapping>

可以如下使用：

<img src="https://www.mshxw.com/skin/sinaskin/image/nopic.gif" width="100" height="100">

注意：不，不能单独使用JSP来完成此操作，因为它是不适合此任务的视图技术。

注意2：请记住这一点，这是一项非常昂贵（CPU密集型）的任务。您可能需要考虑自己预先缓存或预生成拇指。