java - java中从url加载图片

Question

我使用过Windows 7操作系统，chrome/40.0.2214.93

我尝试使用java从url获取图像

我的java代码是

    public static void main(String[] args) {
    // TODO Auto-generated method stub
     BufferedImage img1 = null;
        BufferedImage img2 = null;
        InputStream inputstream=null;
        URLConnection urlcon=null;
        try {
          URL url1 = new URL("http://rosettacode.org/mw/images/3/3c/Lenna50.jpg");
          URL url2 = new URL("http://rosettacode.org/mw/images/b/b6/Lenna100.jpg");

          urlcon=url1.openConnection();
          urlcon.addRequestProperty("User-Agent","Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.93 Safari/537.36");

          img1 = ImageIO.read(url1.openStream());
          img2 = ImageIO.read(url2.openStream());
        } catch (IOException e) {
          e.printStackTrace();
        }
        int width1 = img1.getWidth(null);
        int width2 = img2.getWidth(null);
        int height1 = img1.getHeight(null);
        int height2 = img2.getHeight(null);
        if ((width1 != width2) || (height1 != height2)) {
          System.err.println("Error: Images dimensions mismatch");
          System.exit(1);
        }
        long diff = 0;
        for (int y = 0; y < height1; y++) {
          for (int x = 0; x < width1; x++) {
            int rgb1 = img1.getRGB(x, y);
            int rgb2 = img2.getRGB(x, y);
            int r1 = (rgb1 >> 16) & 0xff;
            int g1 = (rgb1 >>  8) & 0xff;
            int b1 = (rgb1      ) & 0xff;
            int r2 = (rgb2 >> 16) & 0xff;
            int g2 = (rgb2 >>  8) & 0xff;
            int b2 = (rgb2      ) & 0xff;
            diff += Math.abs(r1 - r2);
            diff += Math.abs(g1 - g2);
            diff += Math.abs(b1 - b2);
          }
        }
        double n = width1 * height1 * 3;
        double p = diff / n / 255.0;
        System.out.println("diff percent: " + (p * 100.0));
}

}

运行应用程序时出现错误

    java.io.IOException: Server returned HTTP response code: 403 for URL: http://rosettacode.org/mw/images/3/3c/Lenna50.jpg
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
    at java.net.URL.openStream(Unknown Source)
    at ImgDiffPercent.main(ImgDiffPercent.java:32)
Exception in thread "main" java.lang.NullPointerException
    at ImgDiffPercent.main(ImgDiffPercent.java:37)

我已经尝试了与此相关的堆栈流指南，但问题仍然没有解决。帮我解决一下。

谢谢...

Answer 1

我尝试了你的代码:

public static void main(String[] args) throws IOException {
    BufferedImage image = ImageIO.read(new URL("http://rosettacode.org/mw/images/3/3c/Lenna50.jpg"));
}

我得到了和你一样的错误:

Exception in thread "main" javax.imageio.IIOException: Can't get input stream from URL!
Caused by: java.io.IOException: Server returned HTTP response code: 403 for URL: http://rosettacode.org/mw/images/3/3c/Lenna50.jpg

您收到的错误是由于服务器的 403 应答所致，而不是由于您的代码所致。

403 Forbidden :

服务器理解该请求，但拒绝满足它。授权不会有帮助，并且不应重复请求。如果请求方法不是 HEAD 并且服务器希望公开为什么请求没有被满足，它应该在实体中描述拒绝的原因。