OpenCV 4.1.2 doc

OpenCV 4.1.2 官方离线手册，方便查询，带目录，检索等，index.html页面为导航页。OpenCV (Open Source Computer Vision Library: http://opencv.org) is an open-source BSD-licensed library that includes several hundreds of computer vision algorithms. The document describes the so-called OpenCV 2.x API, which is essentially a C++ API,