vector<Mat> opencv issues - c++

Question

I am trying to read images of size 19x19 into vector. I have 2429 number of such images. But when I run my code, I am sure some Mat images are not read into the vector. Is it a memory issue. If yes, can anyone help me. I confirmed this after having assert statements in my code.Thank you for the help. EDIT: I removed all the if else statements and replaced it with format specifier. When I am building the design matrix X_train, exactly at ex = 1703 my assertion fails. I checked my image set around those ex values and they look fine. I am not able to understand where I am going wrong.
#include <iostream>
#include <vector>
#include <istream>
#include <fstream>
#include <random>
#include <algorithm>
#include "opencv2/opencv.hpp"
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#define NO_OF_IMAGES 2429
using namespace std;
using namespace cv;
static int colSize = 0;
vector<Mat> read_faces() {
vector<Mat> training_images;
string images_path = "images/train/face";
string suffix = ".pgm";
Mat img(19, 19, CV_8UC1);
for (int i = 0; i < NO_OF_IMAGES; i++) {
img = imread( cv::format("%s%05d.pgm", images_path.c_str(), i), 0 );
training_images.push_back(img);
}
return training_images;
}
vector<Mat> extract_train_test_set(
vector<Mat> faces/**< [in] vector of faces or matrices*/,
vector<Mat> &test_set /**< [out] 10% of images*/) {
/**
* Randomly select 90% of these images and collect them into a set training_set and
* the rest 10% in test_set.
*/
int percentage_train = (0.9f * NO_OF_IMAGES);
vector<Mat> training_set;
for (int i = 0; i < percentage_train; i++) {
Mat img = faces[i];
assert(img.empty() == false);
training_set.push_back(img);
}
for (int i = percentage_train; i < NO_OF_IMAGES; i++) {
Mat img = faces[i];
assert(img.empty() == false);
test_set.push_back(img);
}
return training_set;
}
int main(int argc, char **argv) {
vector<Mat> faces = read_faces(); /**< Reading faces into a vector of matrices. */
random_shuffle(faces.begin(), faces.end()); /**< Shuffle the faces vector for creating a training set*/
cout << faces.size() << endl; /**< Size of the vector of faces is 2429*/
vector<Mat> training_set; /**< 90% images i.e 2186 are test images. */
vector<Mat> test_set; /**< 10% images i.e 243 are test images. */
training_set = extract_train_test_set(faces, test_set);
cout << " Training set size " << training_set.size() << endl;
cout << " Test set size " << test_set.size() << endl;
int dim = training_set[0].rows * training_set[0].cols; /**< 361 dimension vector. */
Mat X_train(dim, training_set.size(), CV_8UC1); /**< 361 rows and 2186 columns.*/
Mat m(19, 19, CV_8UC1);
int ex = 0; /**< Counter for indexing the images */
while (ex < training_set.size()) {
m = training_set[ex];/**< Retrieve the image from training vector. */
for (int i = 0; i < 19; i++) {
for (int j = 0; j < 19; j++) {
assert(m.empty() == false);
X_train.at<uchar>(colSize, ex) = m.at<uchar>(i, j); //each image is a 361 element vector
colSize++;
}
}
ex++; /**< Continue to next image. */
colSize = 0; /**< Set to zero so as to continue to next image. That is a reset row index for next image.*/
}
ofstream file_handle("images/train.dat", ios::trunc);
file_handle << X_train;
file_handle.close();
cout << "Height " << X_train.rows << " Width " << X_train.cols << endl;
waitKey(0);
return 0;
}

Answer 1

I got it working. Instead of looping across the image in which I manually set 19 rows and 19 cols (given that each image as 19x19), I used that Mat's class members 'rows' and 'cols'. Solution I found is just replacement with the following:
while (ex < training_set.size()) {
m = training_set[ex];/**< Retrieve the image from training vector. */
cout << "Fine!! " << ex << endl;
assert(m.empty() == false);
for (int i = 0; i < m.rows; i++) {
for (int j = 0; j < m.cols; j++) {
X_train.at<uchar>(colSize, ex) = m.at<uchar>(i, j); //each image is a 361 element vector
colSize++;
}
}
ex++; /**< Continue to next image. */
colSize = 0; /**< Set to zero so as to continue to next image. That is a reset row index for next image.*/
}