getOptimalNewCameraMatrix(cv::InputArray _cameraMatrix,cv::InputArray _distCoeffs,cv::Size imgSize, double alpha, cv::Size newImgSize,cv::Rect* validPixROI, bool centerPrincipalPoint)

 icvGetRectangles(cameraMatrix, distCoeffs, 0, 0, imgSize, inner, outer);// Projection mapping inner rectangle to viewportdouble fx0 = (newImgSize.width) / inner.width;double fy0 = (newImgSize.height) / inner.height;double cx0 = -fx0 * inner.x;double cy0 = -fy0 * inner.y;// Projection mapping outer rectangle to viewportdouble fx1 = (newImgSize.width) / outer.width;double fy1 = (newImgSize.height) / outer.height;double cx1 = -fx1 * outer.x;double cy1 = -fy1 * outer.y;// Interpolate between the two optimal projectionsM[0][0] = fx0*(1 - alpha) + fx1*alpha;M[1][1] = fy0*(1 - alpha) + fy1*alpha;M[0][2] = cx0*(1 - alpha) + cx1*alpha;M[1][2] = cy0*(1 - alpha) + cy1*alpha;

for (y = k = 0; y < N; y++) //opencv 默认为 9for (x = 0; x < N; x++)pts[k++] = cvPoint2D32f((float)x*imgSize.width / (N - 1),(float)y*imgSize.height / (N - 1));
cvUndistortPoints2(_pts, _pts, cameraMatrix, distCoeffs, R, newCameraMatrix);
float iX0 = -FLT_MAX, iX1 = FLT_MAX, iY0 = -FLT_MAX, iY1 = FLT_MAX;
float oX0 = FLT_MAX, oX1 = -FLT_MAX, oY0 = FLT_MAX, oY1 = -FLT_MAX;
// find the inscribed rectangle.
// the code will likely not work with extreme rotation matrices (R) (>45%)
for (y = k = 0; y < N; y++)for (x = 0; x < N; x++){CvPoint2D32f p = pts[k++];oX0 = MIN(oX0, p.x);oX1 = MAX(oX1, p.x);oY0 = MIN(oY0, p.y);oY1 = MAX(oY1, p.y);if (x == 0)iX0 = MAX(iX0, p.x);if (x == N - 1)iX1 = MIN(iX1, p.x);if (y == 0)iY0 = MAX(iY0, p.y);if (y == N - 1)iY1 = MIN(iY1, p.y);}inner = cv::Rect_<float>(iX0, iY0, iX1 - iX0, iY1 - iY0);outer = cv::Rect_<float>(oX0, oY0, oX1 - oX0, oY1 - oY0);