java中的图片按比例缩放功能

java中的图片按比例缩放功能
1. 按固定长宽进行缩放

    /*
     * 图片缩放,w，h为缩放的目标宽度和高度
     * src为源文件目录，dest为缩放后保存目录
     */
    public static void zoomImage(String src,String dest,int w,int h) throws Exception {
        
        double wr=0,hr=0;
        File srcFile = new File(src);
        File destFile = new File(dest);

        BufferedImage bufImg = ImageIO.read(srcFile); //读取图片
        Image Itemp = bufImg.getScaledInstance(w, h, bufImg.SCALE_SMOOTH);//设置缩放目标图片模板
        
        wr=w*1.0/bufImg.getWidth();     //获取缩放比例
        hr=h*1.0 / bufImg.getHeight();

        AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(wr, hr), null);
        Itemp = ato.filter(bufImg, null);
        try {
            ImageIO.write((BufferedImage) Itemp,dest.substring(dest.lastIndexOf(".")+1), destFile); //写入缩减后的图片
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }
2. 按固定文件大小进行缩放
   
    /*
     * 图片按比率缩放
     * size为文件大小
     */
    public static void zoomImage(String src,String dest,Integer size) throws Exception {
        File srcFile = new File(src);
        File destFile = new File(dest);
        
        long fileSize = srcFile.length();
        if(fileSize < size * 1024)   //文件大于size k时，才进行缩放,注意：size以K为单位
            return;
        
        Double rate = (size * 1024 * 0.5) / fileSize; // 获取长宽缩放比例
        
        BufferedImage bufImg = ImageIO.read(srcFile);
        Image Itemp = bufImg.getScaledInstance(bufImg.getWidth(), bufImg.getHeight(), bufImg.SCALE_SMOOTH);
            
        AffineTransformOp ato = new AffineTransformOp(AffineTransform.getScaleInstance(rate, rate), null);
        Itemp = ato.filter(bufImg, null);
        try {
            ImageIO.write((BufferedImage) Itemp,dest.substring(dest.lastIndexOf(".")+1), destFile);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

https://www.cnblogs.com/a8167270/p/5103395.html

问 题

 

The following code always seems to fail:

    URL url = new URL("http://userserve-ak.last.fm/serve/126/8636005.jpg");
    Image img = ImageIO.read(url);
    System.out.println(img);

I've checked the url, and it is a valid jpg image. The error I get is:

Exception in thread "main" javax.imageio.IIOException: Can't get input stream from URL!
at javax.imageio.ImageIO.read(ImageIO.java:1385)
at maestro.Main2.main(Main2.java:25)

Caused by: java.net.ConnectException: Connection timed out
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:310)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:176)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:163)
at java.net.Socket.connect(Socket.java:546)
at java.net.Socket.connect(Socket.java:495)
at sun.net.NetworkClient.doConnect(NetworkClient.java:174)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:409)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:530)
at sun.net.www.http.HttpClient.(HttpClient.java:240)
at sun.net.www.http.HttpClient.New(HttpClient.java:321)
at sun.net.www.http.HttpClient.New(HttpClient.java:338)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:814)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:755)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:680)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1005)
at java.net.URL.openStream(URL.java:1029)
at javax.imageio.ImageIO.read(ImageIO.java:1383)
... 1 more

Java Result: 1

What does this mean? Funny thing is, if I change my internet-connection to that of the neighbour's wireless, it suddenly works.

解决方案:

This worked for me. :)

URL url = new URL("http://userserve-ak.last.fm/serve/126/8636005.jpg");
Image image = ImageIO.read(url.openStream());
System.out.println(image);

I know I am late. Since, even I faced the same issue, thought of putting as it would help some one. :)

http://www.it1352.com/544832.html