OpencCV: calcOpticalFlowSF function - c++

Question

I try to use the calcOpticalFlowSF() function, but when I launch it, the programm doesn't repond, here the part of the code that use it:
frame1 = cv::imread("frame10.png");
frame2 = cv::imread("frame11.png");
if (frame1.empty()) {
cout<<"could not read image oldori"<<endl;
return;
}
if (frame2.empty()) {
cout<<"could not read image ori"<<endl;
return;
}
if (frame1.rows != frame2.rows && frame1.cols != frame2.cols) {
cout<<"images should be of equal sizes "endl;
return;
}
if (frame1.type() != 16 || frame2.type() != 16) {
cout<<"images should be of equal type CV_8UC3")endl;
return;
}
cv::Mat flow;
cv::calcOpticalFlowSF(frame1, frame2, flow, 2, 2, 4);
// calcOpticalFlowSF(frame1, frame1, // doesn't work too.
// flow,
// 3, 2, 4, 4.1, 25.5, 18, 55.0, 25.5, 0.35, 18, 55.0, 25.5, 10);
I know that the error come from the function calcOpticalFlowSF, because if I comment it, the programm works. I use the same pictures as they use in the SimpleFlow demo. If you look here:How to get cv::calcOpticalFlowSF to work? it seems that he got no problem with the function itself...
Do you have an idea why it doesn't work?
thanks,
best regards.

Answer 1

make sure the image is 3-channel, is better to see the docs here
#if 1
#define _CRT_SECURE_NO_WARNINGS
#include <cstdio>
#include <cstdlib>
#include <vector>
#include <stdlib.h>
#include <opencv2/opencv.hpp>
#include "opencv2/optflow.hpp"
#include "opencv2/highgui.hpp"
using namespace std;
using namespace cv;
using namespace cv::optflow;//calcOpticalFlowSF 's namespace
const size_t choice = 2 ;
// choice
// 1 2 3
// calcOpticalFlowFarneback calcOpticalFlowSF calcOpticalFlowPyrLK
void drawOptFlowMap(const Mat& flow, Mat& cflowmap, int step, const Scalar& color) {
// cflowmap is the pre frame with the line of Optical Flow
// flow is a xxx array, store float point
// store the delta of x,y
// step is every step pixel
for (int y = 0; y < cflowmap.rows; y += step)
for (int x = 0; x < cflowmap.cols; x += step)
{
const Point2f& fxy = flow.at< Point2f>(y, x);
line(cflowmap, Point(x, y), Point(cvRound(x + fxy.x), cvRound(y + fxy.y)),
color);
circle(cflowmap, Point(cvRound(x + fxy.x), cvRound(y + fxy.y)), 1, color, -1);
}
}
void drawOptFlowMap(Mat& cflowmap, int step, const Scalar& color, vector<Point2f> &retPts) {
// same as above, retPts is the next frame point
auto it = retPts.begin();
for (int y = 0; y < cflowmap.rows; y += step)
for (int x = 0; x < cflowmap.cols; x += step)
{
line(cflowmap, Point(x, y), *it, color);
circle(cflowmap, *it, 1, color, -1);
it++;
}
}
int main(int argc, char *argv[])
{
Mat flow;//flow = aft - pre
Mat pre = imread("1hf.png", IMREAD_COLOR);
Mat aft = imread("2hf.png", IMREAD_COLOR);// CV_LOAD_IMAGE_GRAYSCALE gray ; IMREAD_COLOR color
if (pre.empty() || aft.empty()){
printf("Unable to load the image");
return 1;
}
Mat cflow = pre; Mat cflow2 = aft;// store the 3-channel mat of frame, cflow is for show color with line
cvtColor(pre, pre, CV_BGR2GRAY);
cvtColor(aft, aft, CV_BGR2GRAY);
//below parameter of calcOpticalFlowPyrLK
vector<Point2f> prePts;
size_t step = 10;
vector<Point2f> nextPts(pre.rows * pre.cols);
vector<uchar> status;
vector<float> err;
TermCriteria termcrit(CV_TERMCRIT_ITER | CV_TERMCRIT_EPS, 20, 0.03);
switch (choice)
{
case 1:// calcOpticalFlowFarneback
calcOpticalFlowFarneback(pre, aft, flow, 0.5, 3, 15, 3, 5, 1.2, 0); // info in the flow; note that input mat should in 1-channel
drawOptFlowMap(flow, cflow, 10, CV_RGB(0, 255, 0)); break;
case 2:// calcOpticalFlowSF
calcOpticalFlowSF(cflow, cflow2,
flow,
3, 2, 4, 4.1, 25.5, 18, 55.0, 25.5, 0.35, 18, 55.0, 25.5, 10);// info in the flow; note that input mat should in 3-channel
drawOptFlowMap(flow, cflow, 10, CV_RGB(0, 255, 0)); break;
case 3:// calcOpticalFlowPyrLK
for (int y = 0; y < pre.rows; y += step)
for (int x = 0; x < pre.cols; x += step)
{
prePts.push_back(Point(x, y));
}
// above get a point vector in step
calcOpticalFlowPyrLK(pre, aft, prePts, nextPts, status, err, Size(31, 31), 3, termcrit, 0, 0.001);// info in the flow; note that input mat should in 1-channel
drawOptFlowMap(cflow, step, CV_RGB(0, 255, 0), nextPts);
break;
default:
break;
}
imshow("pre", pre);
imshow("after", aft);
//cflow is the pre with OpticalFlow line
imshow("pre with OpticalFlow line", cflow);
waitKey(0);
return 0;
}
#endif