How to change if i only wanna to detect half of the image using cvgoodfeaturetotrack

Question

cvGoodFeaturesToTrack (frame1_1C, eig_image, temp_image, frame1_features, &number_of_features, .01, .01, NULL);

What value can i put in the mask parameter if i want to detect only half of the image??

Answer 1

Modify the input image to the function to contain only the part of the image that you want to calculate the good features in.

frame1_1C = frame1_1C(Range(x1,y1), Range(x2,y2));

Answer 2

You could use 0 - for not considering pixek and 255 to consider. The code to select the left half of your image (img) would be:

cv::Mat mask(img.size(), CV_8UC1);       // create mask mat
mask.setTo(0);                           // initialize with 0         
cv::Mat(mask, cv::Rect(0,0, mask.cols / 2, mask.rows)).setTo(255); // set the left half to 255