mac 下 ndk 编译 open cv

1、下载 opencv 源代码：

wget https://github.com/opencv/opencv/archive/3.3.0.zip -O opencv_3.3.0.zip

2、配置环境变量 ```

// 文件输入以下内容
# android sdk
export ANDROID_SDK=/root/android/android-sdk-linux
export PATH=$ANDROID_SDK:$PATH

# android ndk
export ANDROID_NDK=/root/android/android-ndk-r15b
export PATH=$ANDROID_NDK:$PATH

source ~/.bash_profile

安装 ant：brew install ant

3、替换 sdk 里的 tools (密码:22ax) 为旧版，新版的 sdk 里的 tools/android 命令简化了，不能生成 android 项目，会报以下错误：

The "android" command is deprecated.
For manual SDK, AVD, and project management, please use Android Studio.
For command-line tools, use tools/bin/sdkmanager and tools/bin/avdmanager
*************************************************************************
Invalid or unsupported command "--silent create lib-project --path /Users/colbert/Documents/Works/Java/opencv-3.3.0/platforms/build_android_arm --target lib_target_sdk_target-NOTFOUND --name OpenCV --package org.opencv"

4、运行 ./scripts/cmake_android_arm.sh

cd opencv-3.3.0/platforms
./scripts/cmake_android_arm.sh
cd build_android_arm
make -j8