Reading Access Violations in FeatureDetector OpenCV 2.4.5

Question

I tried a lot of image matching code samples in OpenCV 2.4.5 , and I changed that code. I found the error code:

Unhandled exception at 0x585a7090 in testing.exe: 0xC0000005: Access violation reading location 0x00000000. 

Its error in featureDetector->detect(queryImage, queryKeypoints) .

I can not find a solution to this problem. Please help me.

 #include <opencv2\highgui\highgui.hpp> #include <opencv2\features2d\features2d.hpp> #include <opencv2\contrib\contrib.hpp> #include <iostream> #include <fstream> #include <conio.h> #include <string> using namespace std; using namespace cv; static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames); static bool readImages(const string& queryImageName, Mat& queryImage); static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames); static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, const vector<Mat>& trainImages, vector<vector<KeyPoint>>& trainKeypoints, Ptr<FeatureDetector>& featureDetector); static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames) { trainFilenames.clear(); ifstream file(filename.c_str()); if(!file.is_open()) { cout << "File can't open" << endl; return; } size_t pos = filename.rfind("\\"); char dlmtr = '\\'; if(pos == String::npos) { pos = filename.rfind('/'); dlmtr = '/'; } dirName = pos == string::npos ? "" : filename.substr(0, pos) + dlmtr; while(!file.eof()) { string str; getline(file, str); if(str.empty()) break; trainFilenames.push_back(str); } // end while file.close(); } // end void readTrainFilenames static bool readImages(const string& queryImageName, Mat& queryImage) { cout << "reading images..." << endl; queryImage = imread(queryImageName, CV_LOAD_IMAGE_GRAYSCALE); if(queryImage.empty()) { cout << "query image can not be read. \n"; return false; } // end if return true; } static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames) { cout << "reading training images..." << endl; string trainDirName = "D:/matching_to_many_images/"; readTrainFilenames(trainFilename, trainDirName, trainImageNames); if(trainImageNames.empty()) { cout << "Train image filenames can not be read." << endl; return false; } // end if int readImageCount = 0; for(size_t i = 0; i < trainImageNames.size(); i++) { string filename = trainDirName + trainImageNames[i]; Mat img = imread(filename, CV_LOAD_IMAGE_GRAYSCALE); if(img.empty()) { cout << "Train image " << filename << " can not be read." << endl; } else { readImageCount++; }// end if trainImages.push_back(img); } // end for if(!readImageCount) { cout << "All train images can not be read." << endl; return false; } else { cout << readImageCount << " train images were read." << endl; } cout << endl; return true; } static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, const vector<Mat>& trainImages, vector<vector<KeyPoint>>& trainKeypoints, Ptr<FeatureDetector>& featureDetector){ cout << endl << "Extracting keypoints from images..." << endl; try{ featureDetector->detect(queryImage, queryKeypoints); } catch(Ptr<FeatureDetector> a) { cout << "hmm" << endl; } cout << endl; } // end void detectKeypoints int main() { const string defaultDetectorType = "SURF"; const string defaultDescriptorType = "SURF"; const string defaultMatcherType = "FlannBased"; const string defaultQueryImageName = "D:/matching_to_many_images/query.png"; const string defaultFileWithTrainImages = "D:/matching_to_many_images/train/trainImages.txt"; const string defaultDirToSaveResImages = "D:/matching_to_many_images/results"; Ptr<FeatureDetector> featureDetector; Ptr<DescriptorExtractor> descriptorExtractor; Ptr<DescriptorMatcher> descriptorMatcher; Mat queryImages; vector<Mat> trainImages; vector<string> trainImagesNames; vector<KeyPoint> queryKeypoints; vector<vector<KeyPoint>> trainKeypoints; if(!readImages(defaultQueryImageName, queryImages)) { _getch(); return -1; } // end if if(!readTrainImages(defaultFileWithTrainImages, trainImages, trainImagesNames)) { _getch(); return -1; } detectKeypoints(queryImages, queryKeypoints, trainImages, trainKeypoints, featureDetector); cout << "\n done \n"; _getch(); return 0; } // end main method 

Update:

 #include <opencv2\highgui\highgui.hpp> #include <opencv2\features2d\features2d.hpp> #include <opencv2\contrib\contrib.hpp> #include <iostream> #include <fstream> #include <conio.h> #include <string> using namespace std; using namespace cv; static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames); static bool readImages(const string& queryImageName, Mat& queryImage); static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames); static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, Ptr<FeatureDetector>& featureDetector); static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames) { trainFilenames.clear(); ifstream file(filename.c_str()); if(!file.is_open()) { cout << "File can't open" << endl; return; } size_t pos = filename.rfind("\\"); char dlmtr = '\\'; if(pos == String::npos) { pos = filename.rfind('/'); dlmtr = '/'; } dirName = pos == string::npos ? "" : filename.substr(0, pos) + dlmtr; while(!file.eof()) { string str; getline(file, str); if(str.empty()) break; trainFilenames.push_back(str); } // end while file.close(); } // end void readTrainFilenames static bool readImages(const string& queryImageName, Mat& queryImage) { cout << "reading images..." << endl; queryImage = imread(queryImageName, CV_LOAD_IMAGE_GRAYSCALE); if(queryImage.empty()) { cout << "query image can not be read. \n"; return false; } // end if return true; } static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames) { cout << "reading training images..." << endl; string trainDirName = "D:/matching_to_many_images/"; readTrainFilenames(trainFilename, trainDirName, trainImageNames); if(trainImageNames.empty()) { cout << "Train image filenames can not be read." << endl; return false; } // end if int readImageCount = 0; for(size_t i = 0; i < trainImageNames.size(); i++) { string filename = trainDirName + trainImageNames[i]; Mat img = imread(filename, CV_LOAD_IMAGE_GRAYSCALE); if(img.empty()) { cout << "Train image " << filename << " can not be read." << endl; } else { readImageCount++; }// end if trainImages.push_back(img); } // end for if(!readImageCount) { cout << "All train images can not be read." << endl; return false; } else { cout << readImageCount << " train images were read." << endl; } cout << endl; return true; } static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, Ptr<FeatureDetector>& featureDetector){ cout << endl << "Extracting keypoints from images..." << endl; featureDetector->detect(queryImage, queryKeypoints); cout << endl; } // end void detectKeypoints int main() { const string defaultDetectorType = "SURF"; const string defaultDescriptorType = "SURF"; const string defaultMatcherType = "FlannBased"; const string defaultQueryImageName = "D:/matching_to_many_images/query.png"; const string defaultFileWithTrainImages = "D:/matching_to_many_images/train/trainImages.txt"; const string defaultDirToSaveResImages = "D:/matching_to_many_images/results"; Ptr<FeatureDetector> featureDetector; Ptr<DescriptorExtractor> descriptorExtractor; Ptr<DescriptorMatcher> descriptorMatcher; Mat queryImages; vector<Mat> trainImages; vector<string> trainImagesNames; vector<KeyPoint> queryKeypoints; vector<vector<KeyPoint>> trainKeypoints; if(!readImages(defaultQueryImageName, queryImages)) { _getch(); return -1; } // end if if(!readTrainImages(defaultFileWithTrainImages, trainImages, trainImagesNames)) { _getch(); return -1; } detectKeypoints(queryImages, queryKeypoints, featureDetector); cout << "\n done \n"; _getch(); return 0; } // end main method 

SOLVED PROBLEMS:

 #include <opencv2\highgui\highgui.hpp> #include <opencv2\features2d\features2d.hpp> #include <opencv2\contrib\contrib.hpp> #include <opencv2\nonfree\nonfree.hpp> #include <iostream> #include <fstream> #include <conio.h> #include <string> using namespace std; using namespace cv; const string defaultDetectorType = "SURF"; const string defaultDescriptorType = "SURF"; const string defaultMatcherType = "FlannBased"; const string defaultQueryImageName = "D:/matching_to_many_images/query.png"; const string defaultFileWithTrainImages = "D:/matching_to_many_images/train/trainImages.txt"; const string defaultDirToSaveResImages = "D:/matching_to_many_images/results"; static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames); static bool readImages(const string& queryImageName, Mat& queryImage); static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames); static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, Ptr<FeatureDetector>& featureDetector); static bool createDetectorDescriptorMatcher(const string& detectorType, const string& descriptorType, const string& matcherType, Ptr<FeatureDetector>& featureDetector, Ptr<DescriptorExtractor>& descriptorExtractor, Ptr<DescriptorMatcher>& descriptorMatcher); static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames) { trainFilenames.clear(); ifstream file(filename.c_str()); if(!file.is_open()) { cout << "File can't open" << endl; return; } size_t pos = filename.rfind("\\"); char dlmtr = '\\'; if(pos == String::npos) { pos = filename.rfind('/'); dlmtr = '/'; } dirName = pos == string::npos ? "" : filename.substr(0, pos) + dlmtr; while(!file.eof()) { string str; getline(file, str); if(str.empty()) break; trainFilenames.push_back(str); } // end while file.close(); } // end void readTrainFilenames static bool readImages(const string& queryImageName, Mat& queryImage) { cout << "reading images..." << endl; queryImage = imread(queryImageName, CV_LOAD_IMAGE_GRAYSCALE); if(queryImage.empty()) { cout << "query image can not be read. \n"; return false; } // end if return true; } static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames) { cout << "reading training images..." << endl; string trainDirName = "D:/matching_to_many_images/"; readTrainFilenames(trainFilename, trainDirName, trainImageNames); if(trainImageNames.empty()) { cout << "Train image filenames can not be read." << endl; return false; } // end if int readImageCount = 0; for(size_t i = 0; i < trainImageNames.size(); i++) { string filename = trainDirName + trainImageNames[i]; Mat img = imread(filename, CV_LOAD_IMAGE_GRAYSCALE); if(img.empty()) { cout << "Train image " << filename << " can not be read." << endl; } else { readImageCount++; }// end if trainImages.push_back(img); } // end for if(!readImageCount) { cout << "All train images can not be read." << endl; return false; } else { cout << readImageCount << " train images were read." << endl; } cout << endl; return true; } static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, Ptr<FeatureDetector>& featureDetector){ cout << endl << "Extracting keypoints from images..." << endl; if(queryImage.empty()) { cout << "Query Image EMPTY" << endl; } else{ cout << "Query Image FILLED" << endl; } featureDetector->detect(queryImage, queryKeypoints); cout << endl; } // end void detectKeypoints static bool createDetectorDescriptorMatcher(const string& detectorType, const string& descriptorType, const string& matcherType, Ptr<FeatureDetector>& featureDetector, Ptr<DescriptorExtractor>& descriptorExtractor, Ptr<DescriptorMatcher>& descriptorMatcher) { cout << "Creating feature detector, descriptor extractor and descriptor matcher ... " << endl; featureDetector = FeatureDetector::create(detectorType); descriptorExtractor = DescriptorExtractor::create(descriptorType); descriptorMatcher = DescriptorMatcher::create(matcherType); cout << endl; if(featureDetector.empty()) { cout << "feature detector empty" << endl; } if(descriptorExtractor.empty()) { cout << "descriptor extractor empty" << endl; } if(descriptorMatcher.empty()) { cout << "descriptor matcher empty" << endl; } bool isCreated = !(featureDetector.empty() || descriptorExtractor.empty() || descriptorMatcher.empty()); if(!isCreated) { cout << "can not create feature detector or descriptor extractor or descriptor matcher of given types." << endl; } // end if return isCreated; } // end void createDetectorDescriptorMatcher int main() { initModule_nonfree(); string detectorType = defaultDetectorType; string descriptorType = defaultDetectorType; string matcherType = defaultMatcherType; string queryImageName = defaultQueryImageName; string fileWithTrainImages = defaultFileWithTrainImages; string dirToSaveResImages = defaultDirToSaveResImages; Ptr<FeatureDetector> featureDetector = FeatureDetector::create("SURF"); Ptr<DescriptorExtractor> descriptorExtractor = DescriptorExtractor::create("SURF"); Ptr<DescriptorMatcher> descriptorMatcher; if(!createDetectorDescriptorMatcher(detectorType, descriptorType, matcherType, featureDetector, descriptorExtractor, descriptorMatcher)) { _getch(); return -1; } Mat queryImages; vector<Mat> trainImages; vector<string> trainImagesNames; vector<KeyPoint> queryKeypoints; vector<vector<KeyPoint>> trainKeypoints; if(!readImages(defaultQueryImageName, queryImages)) { _getch(); return -1; } // end if if(!readTrainImages(defaultFileWithTrainImages, trainImages, trainImagesNames)) { _getch(); return -1; } detectKeypoints(queryImages, queryKeypoints, featureDetector); cout << "\n done \n"; _getch(); return 0; } // end main method 

FULL SAMPLE CODES CONNECTED TO MANY IMAGES:

 #include <opencv2\highgui\highgui.hpp> #include <opencv2\features2d\features2d.hpp> #include <opencv2\contrib\contrib.hpp> #include <opencv2\nonfree\nonfree.hpp> #include <iostream> #include <fstream> #include <conio.h> #include <string> using namespace std; using namespace cv; const string defaultDetectorType = "SURF"; const string defaultDescriptorType = "SURF"; const string defaultMatcherType = "FlannBased"; const string defaultQueryImageName = "D:/matching_to_many_images/query.png"; const string defaultFileWithTrainImages = "D:/matching_to_many_images/train/trainImages.txt"; const string defaultDirToSaveResImages = "D:/matching_to_many_images/results"; static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames); static bool readImages(const string& queryImageName, Mat& queryImage); static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames); static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, const vector<Mat>& trainImages, vector<vector<KeyPoint>>& trainKeypoints, Ptr<FeatureDetector>& featureDetector); static bool createDetectorDescriptorMatcher(const string& detectorType, const string& descriptorType, const string& matcherType, Ptr<FeatureDetector>& featureDetector, Ptr<DescriptorExtractor>& descriptorExtractor, Ptr<DescriptorMatcher>& descriptorMatcher); static void computeDescriptors(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, Mat& queryDescriptors, const vector<Mat>& trainImages, vector<vector<KeyPoint>>& trainKeypoints, vector<Mat>& trainDescriptors, Ptr<DescriptorExtractor>& descriptorExtractor); static void matchDescriptors(const Mat& queryDescriptors, const vector<Mat>& trainDescriptors, vector<DMatch>& matches, Ptr<DescriptorMatcher>& descriptorMatcher); static void maskMatchesByTrainImgIdx(const vector<DMatch>& matches, int trainImgIdx, vector<char>& mask); static void readTrainFilenames(const string& filename, string& dirName, vector<string>& trainFilenames) { trainFilenames.clear(); ifstream file(filename.c_str()); if(!file.is_open()) { cout << "File can't open" << endl; return; } size_t pos = filename.rfind("\\"); char dlmtr = '\\'; if(pos == String::npos) { pos = filename.rfind('/'); dlmtr = '/'; } dirName = pos == string::npos ? "" : filename.substr(0, pos) + dlmtr; while(!file.eof()) { string str; getline(file, str); if(str.empty()) break; trainFilenames.push_back(str); } // end while file.close(); } // end void readTrainFilenames static bool readImages(const string& queryImageName, Mat& queryImage) { cout << "reading images..." << endl; queryImage = imread(queryImageName, CV_LOAD_IMAGE_GRAYSCALE); if(queryImage.empty()) { cout << "query image can not be read. \n"; return false; } // end if return true; } static bool readTrainImages(const string& trainFilename, vector<Mat>& trainImages, vector<string>& trainImageNames) { cout << "reading training images..." << endl; string trainDirName = "D:/matching_to_many_images/"; readTrainFilenames(trainFilename, trainDirName, trainImageNames); if(trainImageNames.empty()) { cout << "Train image filenames can not be read." << endl; return false; } // end if int readImageCount = 0; for(size_t i = 0; i < trainImageNames.size(); i++) { string filename = trainDirName + trainImageNames[i]; Mat img = imread(filename, CV_LOAD_IMAGE_GRAYSCALE); if(img.empty()) { cout << "Train image " << filename << " can not be read." << endl; } else { readImageCount++; }// end if trainImages.push_back(img); } // end for if(!readImageCount) { cout << "All train images can not be read." << endl; return false; } else { cout << readImageCount << " train images were read." << endl; } cout << endl; return true; } static void detectKeypoints(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, const vector<Mat>& trainImages, vector<vector<KeyPoint>>& trainKeypoints, Ptr<FeatureDetector>& featureDetector){ cout << endl << "Extracting keypoints from images..." << endl; if(queryImage.empty()) { cout << "Query Image EMPTY" << endl; } else{ cout << "Query Image FILLED" << endl; } featureDetector->detect(queryImage, queryKeypoints); featureDetector->detect(trainImages, trainKeypoints); cout << endl; } // end void detectKeypoints static bool createDetectorDescriptorMatcher(const string& detectorType, const string& descriptorType, const string& matcherType, Ptr<FeatureDetector>& featureDetector, Ptr<DescriptorExtractor>& descriptorExtractor, Ptr<DescriptorMatcher>& descriptorMatcher) { cout << "Creating feature detector, descriptor extractor and descriptor matcher ... " << endl; featureDetector = FeatureDetector::create(detectorType); descriptorExtractor = DescriptorExtractor::create(descriptorType); descriptorMatcher = DescriptorMatcher::create(matcherType); cout << endl; if(featureDetector.empty()) { cout << "feature detector empty" << endl; } if(descriptorExtractor.empty()) { cout << "descriptor extractor empty" << endl; } if(descriptorMatcher.empty()) { cout << "descriptor matcher empty" << endl; } bool isCreated = !(featureDetector.empty() || descriptorExtractor.empty() || descriptorMatcher.empty()); if(!isCreated) { cout << "can not create feature detector or descriptor extractor or descriptor matcher of given types." << endl; } // end if return isCreated; } // end void createDetectorDescriptorMatcher static void computeDescriptors(const Mat& queryImage, vector<KeyPoint>& queryKeypoints, Mat& queryDescriptors, const vector<Mat>& trainImages, vector<vector<KeyPoint>>& trainKeypoints, vector<Mat>& trainDescriptors, Ptr<DescriptorExtractor>& descriptorExtractor) { cout << "computing descriptors for keypoints..." << endl; descriptorExtractor->compute(queryImage, queryKeypoints, queryDescriptors); descriptorExtractor->compute(trainImages, trainKeypoints, trainDescriptors); int totalTrainDesc = 0; for(vector<Mat>::const_iterator tdIter = trainDescriptors.begin(); tdIter != trainDescriptors.end(); tdIter++) totalTrainDesc += tdIter->rows; cout << "Query descriptors count : " << queryDescriptors.rows << "; Total train descriptors count : " << totalTrainDesc << endl; cout << endl; } // end void computeDescriptors static void matchDescriptors(const Mat& queryDescriptors, const vector<Mat>& trainDescriptors, vector<DMatch>& matches, Ptr<DescriptorMatcher>& descriptorMatcher) { cout << "Set train descriptors collection in the matcher and match query descriptors to them..." << endl; TickMeter tm; tm.start(); descriptorMatcher->add(trainDescriptors); descriptorMatcher->train(); tm.stop(); double buildTime = tm.getTimeMilli(); tm.start(); descriptorMatcher->match(queryDescriptors, matches); tm.stop(); double matchTime = tm.getTimeMilli(); CV_Assert(queryDescriptors.rows == (int)matches.size() || matches.empty()); cout << "Number of matches: " << matches.size() << endl; cout << "Build time: " << buildTime << " ms; Match time: " << matchTime << " ms" << endl; cout << endl; } // end void matchDescriptors static void saveResultImages(const Mat& queryImage, const vector<KeyPoint>& queryKeypoints, const vector<Mat>& trainImages, const vector<vector<KeyPoint>> &trainKeypoints, const vector<DMatch>& matches, const vector<string>& trainImageNames, const string& resultDir) { cout << "Save results..." << endl; Mat drawImg; vector<char> mask; for(size_t i = 0; i < trainImages.size(); i++) { if(!trainImages[i].empty()) { maskMatchesByTrainImgIdx(matches, (int)i, mask); drawMatches(queryImage, queryKeypoints, trainImages[i], trainKeypoints[i], matches, drawImg, Scalar(255, 0, 0), Scalar(0, 255, 255), mask); string filename = resultDir + "/res_" + trainImageNames[i]; if(!imwrite(filename, drawImg)) { cout << "Image " << filename << " can not be saved (may be because directory " << resultDir << " does not exist" << endl; } // end if } // end if } } // end void saveResultImages static void maskMatchesByTrainImgIdx(const vector<DMatch>& matches, int trainImgIdx, vector<char>& mask) { mask.resize(matches.size()); fill(mask.begin(), mask.end(), 0); for(size_t i = 0; i < matches.size(); i++) { if(matches[i].imgIdx == trainImgIdx) { mask[i] = 1; } } } // end void maskMatchesByTrainImgIdx int main() { initModule_nonfree(); string detectorType = defaultDetectorType; string descriptorType = defaultDetectorType; string matcherType = defaultMatcherType; string queryImageName = defaultQueryImageName; string fileWithTrainImages = defaultFileWithTrainImages; string dirToSaveResImages = defaultDirToSaveResImages; Ptr<FeatureDetector> featureDetector = FeatureDetector::create("SURF"); Ptr<DescriptorExtractor> descriptorExtractor = DescriptorExtractor::create("SURF"); Ptr<DescriptorMatcher> descriptorMatcher; if(!createDetectorDescriptorMatcher(detectorType, descriptorType, matcherType, featureDetector, descriptorExtractor, descriptorMatcher)) { _getch(); return -1; } Mat queryImages; vector<Mat> trainImages; vector<string> trainImagesNames; vector<KeyPoint> queryKeypoints; vector<vector<KeyPoint>> trainKeypoints; if(!readImages(defaultQueryImageName, queryImages)) { _getch(); return -1; } // end if if(!readTrainImages(defaultFileWithTrainImages, trainImages, trainImagesNames)) { _getch(); return -1; } detectKeypoints(queryImages, queryKeypoints, trainImages, trainKeypoints, featureDetector); Mat queryDescriptors; vector<Mat> trainDescriptors; computeDescriptors(queryImages, queryKeypoints, queryDescriptors, trainImages, trainKeypoints, trainDescriptors, descriptorExtractor); vector<DMatch> matches; matchDescriptors(queryDescriptors, trainDescriptors, matches, descriptorMatcher); saveResultImages(queryImages, queryKeypoints, trainImages, trainKeypoints, matches, trainImagesNames, dirToSaveResImages); cout << "\n done \n"; _getch(); return 0; } // end main method 

Answer 1

The documentation for the FeatureDetector class says that it is an abstract base class, which means that you cannot create an instance of this class. This is an OpenCV error that the compiler does not complain!

Try adding:

 Ptr<FeatureDetector> featureDetector = FeatureDetector::create(defaultDetectorType); 

Update:

My next suggestion would be to reduce complexity. Simplify the main program to the minimum working version:

 int main() { cv::initModule_nonfree(); // to load SURF/SIFT etc. std::vector<cv::KeyPoint> queryKeypoints; cv::Mat queryImage = cv::imread(FILENAME, CV_LOAD_IMAGE_GRAYSCALE); cv::Ptr<FeatureDetector> featureDetector = cv::FeatureDetector::create("SURF"); featureDetector->detect(queryImage, queryKeypoints); } 

If the above version works, start adding additional features (slowly) until you start the current version. As soon as the error returns, you know that the last piece added is the culprit, and you can focus on that.

If the above version does not work, you have at least created an SSCCE which you can fix (with the help of others).

BTW: The error message tells you that your program is trying to read memory location 0x00000000 , which is an indicator that you are using an uninitialized data structure, but I'm not sure where the problem is in your program.

Answer 2

It seems that you did not initialize the Ptr<FeatureDetector> featureDetector; anywhere it's an abstract class