OpenCV中手动安装ippicv（ubuntu）

在安装opencv4.1.0时，卡在

IPPICV: Download: ippicv_2019_lnx_intel64_general_20180723.tgz

这个应该是编译opencv源码的通用问题，主要是网络问题，无法下载ippicv包，这里提供一个手动寻找安装包的方式，步骤如下：

1. 在opencv源代码中获取ippicv的下载地址

首先打开opencv-x.x.x\3rdparty\ippicv\ippicv.cmake文件，分别找到如下语句

set(IPPICV_COMMIT "32e315a5b106a7b89dbed51c28f8120a48b368b4")

 "${OPENCV_IPPICV_URL}"
                 "$ENV{OPENCV_IPPICV_URL}"
                 "https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/"

    if(X86_64)
      set(OPENCV_ICV_NAME "ippicv_2019_lnx_intel64_general_20180723.tgz")
      set(OPENCV_ICV_HASH "c0bd78adb4156bbf552c1dfe90599607")

拼接关键句，获得ippicv_2019_lnx_intel64_general_20180723.tgz的下载地址

https://raw.githubusercontent.com/opencv/opencv_3rdparty/32e315a5b106a7b89dbed51c28f8120a48b368b4/ippicv/ippicv_2019_lnx_intel64_general_20180723.tgz

2. 下载

ippicv_2019_lnx_intel64_general_20180723.tgz

3.修改 ippicv.cmake

将如下

 "${OPENCV_IPPICV_URL}"
                 "$ENV{OPENCV_IPPICV_URL}"
                 "https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/"

中的

"https://raw.githubusercontent.com/opencv/opencv_3rdparty/${IPPICV_COMMIT}/ippicv/"

修改为ippicv安装包所在本地路径

"file:///home/student/SFDN/Downloads"

4. 编译opencv

cmake -D OPENCV_ENABLE_NONFREE=ON ..

5. How to build OpenCV with extra modules

$ cd 
$ cmake -DOPENCV_EXTRA_MODULES_PATH=/modules 
$ make -j5

加上额外模块的编译是
cmake -D OPENCV_ENABLE_NONFREE=ON -DOPENCV_EXTRA_MODULES_PATH=/modules