如何在OpenCV中设置BRISK描述符大小？

Question

BRISK的默认大小为512位。如何生成1024位描述符？

我的部分代码：

...
// create the detector
cv::Ptr<cv::FeatureDetector> detector = new cv::BriskFeatureDetector(threshold, numOctaves);
// create the descriptor extractor - scale invariant and rotation invariant
cv::Ptr<cv::BriskDescriptorExtractor> descriptorExtractor = new cv::BriskDescriptorExtractor();
...
// detect keypoints
detector->detect(imgGray,keypoints);
// extract descriptor
descriptorExtractor->compute(imgGray, keypoints, descriptors);
...