0. 写在最前面

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1. 问题描述

使用PCL编译某个ROS工程时出现这个waring：

** WARNING ** io features related to openni2 will be disabled
** WARNING ** io features related to pcap will be disabled
** WARNING ** io features related to png will be disabled
** WARNING ** visualization features related to openni2 will be disabled

这里其实是3个东西缺了

2. 解决办法

2.1 OpenNI2问题

找到对应log文件后发现是OpenNI没有

Could NOT find OpenNI2 (missing:  OPENNI2_LIBRARY OPENNI2_INCLUDE_DIRS)

所以就安装OpenNI就好：

sudo apt-get install openni2-utils

2.2 png问题

png的问题是由于pcl的cmake文件缺了相关的查找。我装ROS的时候已经默认装了libpng，如果你增加了下面这两句还是有问题，可以考虑装一个这个，但千万要小心，我更新了libpng之后不小心把ROS的东西删了，又得重装一下。

在/usr/lib/x86_64-linux-gnu/cmake/pcl目录下找到PCLConfig.cmake文件，用sudo gedit PCLConfig.cmake，在466行后面（find_openni2()下面）增加这句话：

elseif("${_lib}" STREQUAL "png")
    find_package(PNG)

2.3 pcap问题

理由同上，不过libpcap这个是网络抓取包，一般系统不会帮忙装，需要自己装：

sudo apt-get install libpcap-dev

装完之后在PCLConfig.cmake中添加下面这两句：

elseif("${_lib}" STREQUAL "pcap")
    find_package(PCAP)

这个时候还不行，貌似是因为libpcap在安装的时候不会自己配置cmake。。。。。需要你到cmake的Modules目录下，我的是/usr/share/cmake-3.5/Modules，每个人不一样，里面会有很多的Findxxx.cmake的文件。你需要新建一个FindPCAP.cmake，然后往里面填入以下的内容（这部分来源于这位老哥的github）

# - Try to find libpcap include dirs and libraries
#
# Usage of this module as follows:
#
#     find_package(PCAP)
#
# Variables used by this module, they can change the default behaviour and need
# to be set before calling find_package:
#
#  PCAP_ROOT_DIR             Set this variable to the root installation of
#                            libpcap if the module has problems finding the
#                            proper installation path.
#
# Variables defined by this module:
#
#  PCAP_FOUND                System has libpcap, include and library dirs found
#  PCAP_INCLUDE_DIR          The libpcap include directories.
#  PCAP_LIBRARY              The libpcap library (possibly includes a thread
#                            library e.g. required by pf_ring's libpcap)
#  HAVE_PF_RING              If a found version of libpcap supports PF_RING
#  HAVE_PCAP_IMMEDIATE_MODE  If the version of libpcap found supports immediate mode
find_path(PCAP_ROOT_DIR
    NAMES include/pcap.h
)
find_path(PCAP_INCLUDE_DIR
    NAMES pcap.h
    HINTS ${PCAP_ROOT_DIR}/include
)
set (HINT_DIR ${PCAP_ROOT_DIR}/lib)
# On x64 windows, we should look also for the .lib at /lib/x64/
# as this is the default path for the WinPcap developer's pack
if (${CMAKE_SIZEOF_VOID_P} EQUAL 8 AND WIN32)
    set (HINT_DIR ${PCAP_ROOT_DIR}/lib/x64/ ${HINT_DIR})
endif ()
find_library(PCAP_LIBRARY
    NAMES pcap wpcap
    HINTS ${HINT_DIR}
)
include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(PCAP DEFAULT_MSG
    PCAP_LIBRARY
    PCAP_INCLUDE_DIR
)
include(CheckCXXSourceCompiles)
set(CMAKE_REQUIRED_LIBRARIES ${PCAP_LIBRARY})
check_cxx_source_compiles("int main() { return 0; }" PCAP_LINKS_SOLO)
set(CMAKE_REQUIRED_LIBRARIES)
# check if linking against libpcap also needs to link against a thread library
if (NOT PCAP_LINKS_SOLO)
    find_package(Threads)
    if (THREADS_FOUND)
        set(CMAKE_REQUIRED_LIBRARIES ${PCAP_LIBRARY} ${CMAKE_THREAD_LIBS_INIT})
        check_cxx_source_compiles("int main() { return 0; }" PCAP_NEEDS_THREADS)
        set(CMAKE_REQUIRED_LIBRARIES)
    endif (THREADS_FOUND)
    if (THREADS_FOUND AND PCAP_NEEDS_THREADS)
        set(_tmp ${PCAP_LIBRARY} ${CMAKE_THREAD_LIBS_INIT})
        list(REMOVE_DUPLICATES _tmp)
        set(PCAP_LIBRARY ${_tmp}
            CACHE STRING "Libraries needed to link against libpcap" FORCE)
    else (THREADS_FOUND AND PCAP_NEEDS_THREADS)
        message(FATAL_ERROR "Couldn't determine how to link against libpcap")
    endif (THREADS_FOUND AND PCAP_NEEDS_THREADS)
endif (NOT PCAP_LINKS_SOLO)
include(CheckFunctionExists)
set(CMAKE_REQUIRED_LIBRARIES ${PCAP_LIBRARY})
check_function_exists(pcap_get_pfring_id HAVE_PF_RING)
check_function_exists(pcap_set_immediate_mode HAVE_PCAP_IMMEDIATE_MODE)
check_function_exists(pcap_set_tstamp_precision HAVE_PCAP_TIMESTAMP_PRECISION)
set(CMAKE_REQUIRED_LIBRARIES)
mark_as_advanced(
    PCAP_ROOT_DIR
    PCAP_INCLUDE_DIR
    PCAP_LIBRARY
)