I have been trying to form a small optical flow example with OpenCV for a while now. Everything works except the function call calcOpticalFlowPyrLK, which prints the following failed assertion in the console window:
OpenCV Error: Assertion failed (mytype == typ0 || (CV_MAT_CN(mytype) == CV_MAT_CV(type0) && ((1 << type0) & fixedDepthMask) != 0)) in unknown function, file ......\src\opencv\modules\core\src\matrix.cpp, line 1421
The video that I'm parsing is separated into 300 images, labelled as "caml00000.jpeg", "caml00001.jpeg", ..., "caml00299.jpeg". Here is the code I wrote:
#include <cv.h>
#include "opencv2/highgui/highgui.hpp"
using namespace cv;
using namespace std;
int main( int argc, char** argv ){
char buff[100];
int numFrames=300;
char fileFormat[]="images/caml%05d.jpeg";
string winname="Test Window";
vector<Mat> imgVec(numFrames);
auto itrImg=begin(imgVec);
auto itrEnd=end(imgVec);
vector<Point2f> featuresPrevious;
vector<Point2f> featuresCurrent;
namedWindow( winname, CV_WINDOW_AUTOSIZE );
int fileNum=0;
while(itrImg!=itrEnd){
Mat& imgRef=*itrImg; //get this frame's Mat from the vector iterator
//Calculate the name of the file;
sprintf(buff,fileFormat,fileNum);
string fileName=buff;
//string fileName="kitty.jpg"; //attempted using a static picture as well
cout << fileName << endl;
Mat cImage=imread(fileName, CV_LOAD_IMAGE_GRAYSCALE);
cImage.convertTo(imgRef, CV_8U); //also tried CV_8UC1
featuresPrevious=std::move(featuresCurrent);
goodFeaturesToTrack(imgRef,featuresCurrent,30, 0.01, 30); //calculate the features for use in next iteration
if(!imgRef.data){ //this never executes, so there isn't a problem reading the files
cout << "File I/O Problem!" << endl;
getchar();
return 1;
}
if(fileNum>0){
Mat& lastImgRef=*(itrImg-1); //get the last frame's image
vector<Point2f> featuresNextPos;
vector<char> featuresFound;
vector<int> err;
calcOpticalFlowPyrLK(lastImgRef,imgRef,featuresPrevious,featuresNextPos,featuresFound,err); //problem line
//Draw lines connecting previous position and current position
for(size_t i=0; i<featuresNextPos.size(); i++){
if(featuresFound[i]){
line(imgRef,featuresPrevious[i],featuresNextPos[i],Scalar(0,0,255));
}
}
}
imshow(winname, imgRef);
waitKey(1000/60); //not perfect, but it'll do
++itrImg;
++fileNum;
}
waitKey(0);
return 0;
}
The only thing I've read about this exception is that it is caused when Mats are in different formats, however I've tried reading a static image (see code above regarding "kitty.jpg") and I still get the same failed assertion. Any ideas?
Change line vector<char> featuresFound;
to vector<uchar> featuresFound;
and vector<int> err;
to Mat err;
I can't explain why, but that's how it has to be done.
Edit: As @Sluki said in the comments - err vector has to be stored in floating point precision std::vector or cv::Mat.