如何在OpenCV中进行鱼眼校准后获得裁剪后的图像

Question

我正在尝试在OpenCV 3.2中校准鱼眼相机。这是一个代码：

 Mat newCamMat;
            cameraMatrix= getOptimalNewCameraMatrix(cameraMatrix, distCoeffs, imageSize, 0, imageSize, 0); //Does not change anything

            fisheye::estimateNewCameraMatrixForUndistortRectify(cameraMatrix, distCoeffs, imageSize,
                                                                Matx33d::eye(), newCamMat, 1);
            fisheye::initUndistortRectifyMap(cameraMatrix, distCoeffs, Matx33d::eye(), newCamMat, imageSize,
                                             CV_16SC2, map1, map2);

我在校准中使用了这些标志：

 fisheye::CALIB_FIX_SKEW | fisheye::CALIB_RECOMPUTE_EXTRINSIC | fisheye::CALIB_CHECK_COND

我希望在没有可用区域周围的黑色区域的情况下裁剪图像。对于非鱼眼校准，我通过设置alpha来实现。对于鱼眼，我不知道如何改变它。任何建议？

Desired result (inside the red rectangle)

Calibration result

Answer 1

您可以使用蒙版setTo将Alpha通道值设置为透明。

Mat img = imread("fisheye.png",-1), gray, mask;

cvtColor(img, gray, cv::COLOR_BGR2GRAY);

threshold(gray, mask, 0, 255, cv::THRESH_BINARY_INV);

cvtColor(img, img, cv::COLOR_BGR2BGRA);

img.setTo(Scalar(0,0,0,0),mask);