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I am trying to understand how to get the descriptor for a given KeyPoint in OpenCV. So far my code looks like follows:

#include <iostream>
#include "opencv2/opencv.hpp"

typedef cv::Mat Image;

int main(int argc, const char * argv[])
{

    Image imgA = cv::imread("images/buddhamulticam_total100.png",
                              CV_LOAD_IMAGE_GRAYSCALE);
    Image imgB = cv::imread("images/buddhamulticam_total101.png", 
                            CV_LOAD_IMAGE_GRAYSCALE);

    cv::Ptr<cv::FeatureDetector> detector = 
                    cv::FeatureDetector::create("ORB");
    cv::Ptr<cv::DescriptorExtractor> descriptor = 
                    cv::DescriptorExtractor::create("ORB");

    std::vector<cv::KeyPoint> keyPointsA, keyPointsB;

    keyPointsA.push_back(cv::KeyPoint(0,0,5));
    keyPointsB.push_back(cv::KeyPoint(10,10,5));

    cv::Mat descriptorA, descriptorB;
    descriptor->compute(imgA, keyPointsA, descriptorA);
    descriptor->compute(imgB, keyPointsB, descriptorB);

    std::cout << "DescriptorA (" << descriptorA.rows << "," <<
                descriptorA.cols << ")" << std::endl;
    std::cout << "DescriptorB (" << descriptorB.rows << "," 
              << descriptorB.cols << ")" << std::endl;
    return 0;
}

The problem is that I am getting no data in the descriptor. What am I missing? Could you explain in more detail what are the params passed to the KeyPoint object? I am new to computer vision + OpenCV, so probably a better explanation (than OpenCV's documentation) could help.

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1 回答 1

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您正在尝试在点 (0,0) 和 (10,10) 上计算 ORB，但它们太靠近图像边界，因此 ORB 无法计算这些位置的描述符。ORB（以及其他二进制描述符）将它们过滤掉。

编辑：既然您询问了使用情况，我正在编辑答案。你应该传递整个图像。我将其用作：

Ptr<FeatureDetector> detector = FeatureDetector::create(detector_name);
Ptr<DescriptorExtractor> descriptor = DescriptorExtractor::create(descriptor_name);

detector->detect(imgK, kp);
descriptor->compute(imgK, kp, desc);
于 2013-10-20T10:02:46.540 回答