Question

我想要显示img1.png。但是，如果找到文件时出错，我希望显示备份missing.png。 HTML中是否有一种方法可以使用if语句或异常？

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include <iostream>

using namespace std;
using namespace cv;

int main(int argc, char** argv)
{
    Mat src, src_gray, flipped, display;

    if (argc < 2)
    {
        std::cerr<<"No input image specified\n";
        return -1;
    }

    // Read the image
    src = imread( argv[1], 1 );

    if( src.empty() )
    {
        std::cerr<<"Invalid input image\n";
        return -1;
    }

    flip( src, flipped, 1 );
    hconcat( src,flipped, flipped );
    hconcat( flipped, src, src );

    flip( src, flipped, 0 );
    vconcat( src,flipped, flipped );
    vconcat( flipped, src, src );

    flip( src, src, -1 );

    // Convert it to gray
    cvtColor( src, src_gray, COLOR_BGR2GRAY );

    // Reduce the noise so we avoid false circle detection
    GaussianBlur( src_gray, src_gray, Size(9, 9), 2, 2 );

    // will hold the results of the detection
    std::vector<Vec3f> circles;
    // runs the actual detection
    HoughCircles( src_gray, circles, HOUGH_GRADIENT, 1, 50, 40, 46, 0, 0 );

    // clone the colour, input image for displaying purposes
    display = src.clone();
    Rect rect_src(display.cols / 3, display.rows / 3, display.cols / 3, display.rows / 3 );
    rectangle( display, rect_src, Scalar(255,0,0) );
    for( size_t i = 0; i < circles.size(); i++ )
    {
        Point center(cvRound(circles[i][0]), cvRound(circles[i][1]));
        int radius = cvRound(circles[i][2]);

        Rect r = Rect( center.x-radius, center.y-radius, radius * 2, radius * 2 );
        Rect intersection_rect = r & rect_src;
        if( intersection_rect.width * intersection_rect.height >  r.width * r.height / 3 )
        {
            // circle center
            circle( display, center, 3, Scalar(0,255,0), -1, 8, 0 );
            // circle outline
            circle( display, center, radius, Scalar(0,0,255), 3, 8, 0 );
        }

    }

    // shows the results
    imshow( "results", display(rect_src));
    // get user key
    waitKey();

    return 0;
}

我在所有不明白该做的行上都加了一个问号。

Answer 1

查看答案docs

它表示你可以按照以下方式进行操作

<img src="img1.png" alt="Image not found" onError="this.onerror=null;this.src='missing.png';" />

其中onerror是一个Javascript函数。有关onerror

的详细信息，请参阅http://sqlfiddle.com/#!9/d78e2/5

如果在HTML上找不到第一个，请备份img

1 个答案: