在編譯OpenCV以及其附加模塊時(shí)，有時(shí)會(huì)需要一些第三方的庫(kù)，如果本地沒(méi)有，會(huì)自動(dòng)下載，下載地址一般為GitHub，結(jié)果當(dāng)然就是卡死在那里，根本無(wú)法下載，下面教大家如何解決這種問(wèn)題。

問(wèn)題重現(xiàn)

比如我在使用cmake配置的過(guò)程中出現(xiàn)以下情況：

Call Stack (most recent call first):

/home/ryan/build/opencv_contrib-master/modules/dnn/cmake/download_protobuf.cmake:23 (ocv_download)

/home/ryan/build/opencv_contrib-master/modules/dnn/cmake/download_protobuf.cmake:51 (ocv_protobuf_download)

/home/ryan/build/opencv_contrib-master/modules/dnn/cmake/OpenCVFindLibProtobuf.cmake:30 (include)

/home/ryan/build/opencv_contrib-master/modules/dnn/CMakeLists.txt:38 (include)

-- Downloading v3.1.0/protobuf-cpp-3.1.0.tar.gz...

解決思路

從上面的日志中可以得到以下信息：

需要下載protobuf-cpp-3.1.0.tar.gz這個(gè)文件

最先報(bào)錯(cuò)的是download_protobuf.cmake這個(gè)文件

一般情況下，最先報(bào)錯(cuò)的那個(gè)文件能獲得一些與錯(cuò)誤相關(guān)的信息，于是，我們打開(kāi)這個(gè)文件，如下

set(PROTOBUF_CPP_NAME "libprotobuf")

set(PROTOBUF_CPP_DOWNLOAD_HASH "bd5e3eed635a8d32e2b99658633815ef")

set(PROTOBUF_CPP_PATH "${CMAKE_CURRENT_BINARY_DIR}/3rdparty/protobuf/sources") # /protobuf-3.1.0 subdirectory

set(OPENCV_PROTOBUF_CPP_DOWNLOAD_URL ${OPENCV_PROTOBUF_URL};$ENV{OPENCV_PROTOBUF_URL};https://github.com/google/protobuf/releases/download/)

function(ocv_protobuf_download file ID)

if(DEFINED ${ID}_DOWNLOADED_HASH

AND ${ID}_DOWNLOADED_HASH STREQUAL ${ID}_DOWNLOAD_HASH

AND EXISTS ${${ID}_PATH})

# Files have been downloaded and checked by the previous CMake run

return()

else()

if(EXISTS ${${ID}_PATH})

message(STATUS "${${ID}_NAME}: Removing previous unpacked files: ${${ID}_PATH}")

file(REMOVE_RECURSE ${${ID}_PATH})

endif()

endif()

unset(${ID}_DOWNLOADED_HASH CACHE)

file(MAKE_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/.download)

file(WRITE "${CMAKE_CURRENT_SOURCE_DIR}/.download/.gitignore" "*\n")

ocv_download(PACKAGE ${file}

HASH ${${ID}_DOWNLOAD_HASH}

URL ${OPENCV_${ID}_DOWNLOAD_URL}

DOWNLOAD_DIR ${CMAKE_CURRENT_SOURCE_DIR}/.download)

set(${ID}_ARCHIVE "${DOWNLOAD_PACKAGE_LOCATION}")

ocv_assert(EXISTS "${${ID}_ARCHIVE}")

ocv_assert(NOT EXISTS "${${ID}_PATH}")

file(MAKE_DIRECTORY ${${ID}_PATH})

ocv_assert(EXISTS "${${ID}_PATH}")

file(WRITE "${${ID}_PATH}/.gitignore" "*\n")

message(STATUS "${${ID}_NAME}: Unpacking ${file} to ${${ID}_PATH}...")

execute_process(COMMAND ${CMAKE_COMMAND} -E tar xz "${${ID}_ARCHIVE}"

WORKING_DIRECTORY "${${ID}_PATH}"

RESULT_VARIABLE __result)

if(NOT __result EQUAL 0)

message(FATAL_ERROR "${${ID}_NAME}: Failed to unpack ${ID} archive from ${${ID}_ARCHIVE} to ${${ID}_PATH} with error ${__result}")

endif()

ocv_assert(EXISTS "${${ID}_PATH}")

set(${ID}_DOWNLOADED_HASH "${${ID}_DOWNLOAD_HASH}" CACHE INTERNAL "${ID} hash")

#message(STATUS "${${ID}_NAME}: Successfully downloaded")

endfunction()

ocv_protobuf_download(v3.1.0/protobuf-cpp-3.1.0.tar.gz PROTOBUF_CPP)

可以看出，他需要libprotobuf這個(gè)庫(kù)，并且需要下載到 ${CMAKE_CURRENT_BINARY_DIR}/3rdparty/protobuf/sources 目錄下，而下載地址就是 https://github.com/google/protobuf/releases/download/ ，于是我們只要手動(dòng)下載，然后把文件放到這個(gè)目錄下即可。

Ubuntu 16.04下Matlab2014a+Anaconda2+OpenCV3.1+Caffe安裝? http://www.linuxidc.com/Linux/2016-07/132860.htm

Ubuntu 16.04下TensorFlow+Caffe+OpenCV3.1+Theano部署? http://www.linuxidc.com/Linux/2017-01/139503.htm

OpenCV的詳細(xì)介紹：請(qǐng)點(diǎn)這里

OpenCV的下載地址：請(qǐng)點(diǎn)這里

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