在函数中返回 ！_src.empty() 的视频帧'cvtColor'错误

Question

我正在尝试在视频播放时将帧从视频转换为张量。这是我的代码:

#include <iostream>
#include "src/VideoProcessing.h"
#include <opencv2/opencv.hpp>
#include <opencv2/videoio.hpp>
typedef cv::Point3_<float> Pixel;
const uint WIDTH = 224;
const uint HEIGHT = 224;
const uint CHANNEL = 3;
const uint OUTDIM = 128;
void normalize(Pixel &pixel){
pixel.x = (pixel.x / 255.0 - 0.5) * 2.0;
pixel.y = (pixel.y / 255.0 - 0.5) * 2.0;
pixel.z = (pixel.z / 255.0 - 0.5) * 2.0;
}
int main() {
int fps = VideoProcessing::getFPS("trainer.mp4");
unsigned long size = VideoProcessing::getSize("trainer.mp4");
cv::VideoCapture cap("trainer.mp4");
//Check if input video exists
if(!cap.isOpened()){
std::cout<<"Error opening video stream or file"<<std::endl;
return -1;
}
//Create a window to show input video
cv::namedWindow("input video", cv::WINDOW_NORMAL);
//Keep playing video until video is completed
while(true){
cv::Mat frame;
frame.convertTo(frame, CV_32FC3);
cv::cvtColor(frame, frame, cv::COLOR_BGR2RGB); // convert to float; BGR -> RGB
// normalize to -1 & 1
auto* pixel = frame.ptr<Pixel>(0,0);
const Pixel* endPixel = pixel + frame.cols * frame.rows;
for (; pixel != endPixel; pixel++){normalize(*pixel);}
// resize image as model input
cv::resize(frame, frame, cv::Size(WIDTH, HEIGHT));
//Capture frame by frame
bool success = cap.read(frame);
//If frame is empty then break the loop
if (!success){
std::cout << "Found the end of the video" << std::endl;
break;
}
//Show the current frame
cv::imshow("input video", frame);
if (cv::waitKey(10) == 27){
std::cout << "Esc key is pressed by user. Stopping the video" << std::endl;
break;
}
}
//Close window after input video is completed
cap.release();
//Destroy all the opened windows
cv::destroyAllWindows();
std::cout << "Video file FPS: " << fps << std::endl;
std::cout << "Video file size: " << size << std::endl;
return 0;
}

我的目标是在每一帧上运行推理以获得地标。然而，在这个阶段，我看到了这个错误:

terminate called after throwing an instance of 'cv::Exception'
what():  OpenCV(4.1.0) /home/onur/opencv/modules/imgproc/src/color.cpp:182: error: (-215:Assertion failed) !_src.empty() in function 'cvtColor'
Aborted (core dumped)

我哪里错了?

Answer 1

在执行任何转换之前，必须先读取框架。

移动部件

//Capture frame by frame
bool success = cap.read(frame);
//If frame is empty then break the loop
if (!success){
std::cout << "Found the end of the video" << std::endl;
break;
}

后

cv::Mat frame;