▍1. stereo cameras calibration
Given a list of chessboard images, the number of corners (nx, ny) on the chessboards, and a flag: useCalibrated for calibrated (0) or uncalibrated (1: use cvStereoCalibrate(), 2: compute fundamental matrix separately) stereo. Calibrate the cameras and display the rectified results along with the computed disparity images. Usage: ./stereo_calib -w board_width -h board_height [-nr /*dot not view results*/]