在OpenCV中将二维码投影到摄像头时，出现错误答案

【问题标题】：When I project the QR code to the camera in OpenCV, an error occurs在OpenCV中将二维码投影到摄像头时，出现错误
【发布时间】：2021-10-04 15:41:57
【问题描述】：

我想生成一个代码，以便在 QR 码指向相机时播放视频。但我在 warpPerspective 中遇到错误。错误是：OpenCV(4.5.3) 错误：断言失败 (_src.total() > 0) in cv::warpPerspective, 文件 C:\build\master_winpack-build-win64-vc15\opencv\modules\imgproc \src \imgwarp.cpp，第 3144 行找了很多地方都找不到答案，所以来问一下。

#include "opencv2/opencv.hpp"

using namespace cv;
using namespace std;

void main() 
{
    Mat cameraFrame, videoFrame;
    vector<Point2f> bbox;
    double width, height;
    VideoCapture camera(0), video;
    QRCodeDetector qrDecoder;
    string data;
    
    while (camera.read(cameraFrame))
    {
        data = qrDecoder.detectAndDecode(cameraFrame, bbox);

        if (data.length() > 0)
        {
            if (!video.isOpened()) {
                video.open("../data/"+data+".mp4");
                width = video.get(CAP_PROP_FRAME_WIDTH);
                height = video.get(CAP_PROP_FRAME_HEIGHT);
            }
            
            vector<Point2f> v_bbox{ Point2f(0, 0), Point2f(width,0), Point2f(width,height), Point2f(0, height) };
            Mat H = findHomography(v_bbox, bbox);
            video >> videoFrame;
            Mat warpedFrame, warpedMask;

            warpedFrame.copyTo(cameraFrame, warpedMask);

            warpPerspective(videoFrame, warpedFrame, H, cameraFrame.size());
            Mat mask(videoFrame.size(), CV_8UC1, cv::Scalar(255));
            
            warpPerspective(mask, warpedMask, H, cameraFrame.size());
            imshow("warepedFrame", warpedFrame);
            imshow("WarpedMask", warpedMask);
        }
        imshow("cam", cameraFrame);
        waitKey(1);
    }
}

【问题讨论】：

标签： c++ opencv qr-code

【解决方案1】：

问题是您在 warpedFrame 被重置 cameraFrame 填充 warpPerspective 之前调用了 copyTo 方法mat，然后当您将 cameraFrame.size() 传递给 warpPerspective 并使用 cameraFrame.size() 构造掩码垫，您基本上传递的大小为 (0,0)

您所要做的就是在应用透视变换后复制包装的视频叠加层：

#include "opencv2/opencv.hpp"

using namespace cv;
using namespace std;

void main() 
{
    Mat cameraFrame, videoFrame;
    vector<Point2f> bbox;
    double width, height;
    VideoCapture camera(0), video;
    QRCodeDetector qrDecoder;
    string data;
    
    while (camera.read(cameraFrame))
    {
        data = qrDecoder.detectAndDecode(cameraFrame, bbox);

        if (data.length() > 0)
        {
            if (!video.isOpened()) {
                video.open("../data/"+data+".mp4");
                width = video.get(CAP_PROP_FRAME_WIDTH);
                height = video.get(CAP_PROP_FRAME_HEIGHT);
            }
            
            vector<Point2f> v_bbox{ Point2f(0, 0), Point2f(width,0), Point2f(width,height), Point2f(0, height) };
            Mat H = findHomography(v_bbox, bbox);
            video >> videoFrame;
            Mat warpedFrame, warpedMask;
    
            warpPerspective(videoFrame, warpedFrame, H, cameraFrame.size());
            Mat mask(videoFrame.size(), CV_8UC1, cv::Scalar(255));
            
            warpPerspective(mask, warpedMask, H, cameraFrame.size());

            imshow("warepedFrame", warpedFrame);
            imshow("WarpedMask", warpedMask);

            warpedFrame.copyTo(cameraFrame, warpedMask);

        }
        imshow("cam", cameraFrame);
        waitKey(1);
    }
}

【讨论】：