当视差图是CV_8U型时，访问OpenCV中的视差值？

Question

I saw from a previous post that when you obtain the disparity value in the disparity map in open cv with disptype==CV_16S you divide by 16.0 . How about when the disparity map is type CV_8U ?

Do you have to divide by 8.0 to obtain the real disparity value? I haven't found any documentation on this particular type.

Answer 1

You divide by 16 because the original disparity output of StereoSGBM is scaled by 16 and not because of the bit depth/disptype of the disparity.

If you use sgbm->compute(left, right, disp); the output disptype is CV_16S even if you previously initialised disp to be of type CV_8U . Therefore, using convertTo and dividing by 16.f is the correct way. (If you for some reason want to modify disp before you use convertTo and reprojectImageTo3D then I don't know how you would get the real disparity values. It is, however, possible to convertTo CV_8U instead of CV_32F but the results will obviously not be exactly similar.)

Answer 2

Disparity map of CV_8U can be obtained from disparity map of CV_16S type by using imgDisparity16S.convertTo( imgDisparity8U, CV_8UC1, range); where range is calculated as range = 255 / maxVal - minVal and minMaxLoc( imgDisparity16S, &minVal, &maxVal ); So i guess the reciprocal of range ie 1 / range will convert CV_8U to CV_16S and then you can have actual disparity value.

PS : I haven't tried this.