template matching - matchShapes using grayscale images opencv -

according matchshapes documentation, input can either gray scale images or contours. when tried 2 gray scale images, got assertion failed error. upon further exploration, found here mat object has 1d vector , of type cv_32fc2 or cv_32sc2.

using this answer, converted images vector array of float after converting them cv_32fc2. still assertion error.

can tell me how can compare 2 grayscale images using matchshapes function?

update

the error message

  opencv error: assertion failed (contour1.checkvector(2) >= 0 && contour2.checkvector(2) >= 0 && (contour1.depth() == cv_32f || contour1.depth() == cv_32s) && contour1.depth() == contour2.depth()) in matchshapes, file /home/tonystark/opencv/modules/imgproc/src/contours.cpp, line 1936   terminate called after throwing instance of 'cv::exception'   what():  /home/tonystark/opencv/modules/imgproc/src/contours.cpp:1936: error: (-215) contour1.checkvector(2) >= 0 && contour2.checkvector(2) >= 0 && (contour1.depth() == cv_32f || contour1.depth() == cv_32s) && contour1.depth() == contour2.depth() in function matchshapes 

when used

    pkg-config --modversion opencv 

it says version 2.4.9

if break assertion message down, it's checking few things --

1. contour1.checkvector(2) >= 0 && contour2.checkvector(2) >= 0
2. contour1.depth() == cv_32f || contour1.depth() == cv_32s
3. contour1.depth() == contour2.depth()

it sounds aware of parts 2 , 3 above, i'll hazard guess it's failing on part 1.

according opencv documentation, checkvector function

returns n if matrix 1-channel (n x ptdim) or ptdim-channel (1 x n) or (n x 1); negative number otherwise

this unfortunately rather cryptic message. understand it, it's checking dimensionality of input dimension -- in case, failing assertion passing in 2, , verifying dimension greater 0. precludes possibility of having empty array, , verifies other dimension exists. tldr; it's checking if input 1d array of sufficient dimension.

i'd guess error result of passing in vector of vector of points -- instead, have pass in single 'shape' @ time matchshapes, i.e. vector of points

here's little test-case that, although not particularly interesting, should run without problems --

#include <cstdlib> #include <ctime>     #include <iostream>  #include <vector> #include <opencv2/opencv.hpp>  int main(int argc, char* argv[]) {      std::srand(std::time(0));      std::vector<cv::point> random_pointsa;     (int = 0; < 1000; ++i) {       auto rand_x = std::rand() % 255;        auto rand_y = std::rand() % 255;        random_pointsa.emplace_back(rand_x, rand_y);     }      std::vector<cv::point> random_pointsb;     (int = 0; < 1000; ++i) {       auto rand_x = std::rand() % 255;        auto rand_y = std::rand() % 255;        random_pointsb.emplace_back(rand_x, rand_y);     }      auto match_val = cv::matchshapes(random_pointsa, random_pointsb, cv_contours_match_i1, 0);     std::cout << "match val: " << match_val << std::endl; }