opencv - How to pass data to Mat using pointer of image data -

in code, don't want read data rout of images,such as

    cv::mat img_1 = imread("f:\1.tif");

instead wanna read data pointer:

    float* srcimage;//pointer image data     cv::mat img_1(height, width, cv_32fc1, srcimage);

however, found that, way, when used img_1 in following orb function, didn't work

    cv::orb orb; vector<cv::keypoint> keypoints_1; cv::mat descriptors_1; orb(img_1, cv::mat(), keypoints_1, descriptors_1);

how can pass data mat pointer? there difference between imread() function , pass data pointer? or, there special request in cv::orb function ?

thanks much! i'm not familiar opencv, start using few weeks, need solve problem , rest part of code depends on results of part.

orb wants 8bit grayscale image input, not cv_32fc1

Naan