dlib库使用

最近的工作中用到了dlib这个库，该库是一个机器学习的开源库，使用起来很方便，直接包含头文件即可，并且不依赖于其他库（自带图像编解码库源码）。不过由于是开源的，所以bug多少有一些，我在example编译和使用时就遇到了一些问题，总结如下：

1.example编译

按照官网的指导，下载最新的18.18版本dlib，然后解压缩到某个路径。dlib库不用单独编译，只需要编译example，即可看到效果。根据README.txt文件中的步骤，在exmaple文件夹下，执行下面命令即可，

mkdir build

cd build

cmake ..

cmake --build .

但是一般在最后一步会遇到一些问题，导致编译失败，解决方法如下：

1.在dlib/CMakeLists.txt中 project(dlib) 的下一行添加set(Boost_USE_STATIC_LIBS ON)

2.把 if (DLIB_PNG_SUPPORT) （227行左右）这一行以下的这些代码进行注释，其余不变

         # try to find libpng
         #find_package(PNG QUIET)
         # Make sure there isn't something wrong with the version of LIBPNG
         # installed on this system.
         #if (PNG_FOUND)
            #set(CMAKE_REQUIRED_LIBRARIES ${PNG_LIBRARY})
            #CHECK_FUNCTION_EXISTS(png_create_read_struct LIBPNG_IS_GOOD)
         #endif()
         #if (PNG_FOUND AND LIBPNG_IS_GOOD)
            #include_directories(${PNG_INCLUDE_DIR})
            #set (dlib_needed_libraries ${dlib_needed_libraries} ${PNG_LIBRARY})
         #else()
            # If we can't find libpng then statically compile it in.

3.把 if (DLIB_JPEG_SUPPORT) （280行左右）这一行以下的这些代码进行注释，其余不变

         # try to find libjpeg
         #find_package(JPEG QUIET)
         # Make sure there isn't something wrong with the version of libjpeg
         # installed on this system.  Also don't use the installed libjpeg
         # if this is an APPLE system because apparently it's broken (as of 2015/01/01).
         #if (JPEG_FOUND)
            #set(CMAKE_REQUIRED_LIBRARIES ${JPEG_LIBRARY})
            #CHECK_FUNCTION_EXISTS(jpeg_read_header LIBJPEG_IS_GOOD)
         #endif()
         #if (JPEG_FOUND AND LIBJPEG_IS_GOOD AND NOT APPLE)
            #include_directories(${JPEG_INCLUDE_DIR})
            #set (dlib_needed_libraries ${dlib_needed_libraries} ${JPEG_LIBRARY})
         #else()
            # If we can't find libjpeg then statically compile it in.

这样应该就可以编译通过了，编译出的二进制文件应该也可以执行，如果执行时依然报错找不到jpeg或png库，再确认一下CMakeLists文件是否按照上述修改。