How to build OpenCV 2.4.9 for iOS?

Question

I am following these instructions which belong to the openCV doc, but they are really outdated: iOS4 or iOS5 is mentioned, XCode 4.2 installed in /Developer, etc..

It doesn't build, and I have various errors:

All of the initial tests fail: -- Performing Test HAVE_CXX_W - Failed Also:

-- Looking for fseeko
-- Looking for fseeko - not found
-- Looking for unistd.h
-- Looking for unistd.h - not found
-- Looking for sys/types.h
-- Looking for sys/types.h - not found
-- Looking for stdint.h
-- Looking for stdint.h - not found
-- Looking for stddef.h
-- Looking for stddef.h - not found

The configuration looks correct:

-- General configuration for OpenCV 2.4.9 =====================================
--   Version control:               2.4.5-1168-g0a42a3e
--
--   Platform:
--     Host:                        Darwin 12.3.0 i386
--     Target:                      iOS
--     CMake:                       2.8.10
--     CMake generator:             Xcode
--     CMake build tool:            /opt/local/bin/cmakexbuild
--     Xcode:                       4.6.2
[...]
--   Media I/O:
--     ZLib:                        build (ver 1.2.7)
--     JPEG:                        build (ver 90)
--     WEBP:                        NO
--     PNG:                         build (ver 1.5.12)
--     TIFF:                        NO
--     JPEG 2000:                   NO
--     OpenEXR:                     NO
--
--   Video I/O:
--     AVFoundation:                YES
--     QuickTime:                   NO
--     QTKit:                       YES
--     V4L/V4L2:                    NO/NO

But later, I have this first linking error: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool: can't open file: /Users/ant/xcode/opencv/ios/build/iPhoneOS-armv7/3rdparty/libjpeg/OpenCV.build/Release-iphoneos/libjpeg.build/Objects-normal/armv7/jmemansi.o

What is missing on my system to compile OpenCV for iOS ?

Answer 1

As per 3rdParty/libjpeg/CMakeLists.txt:12, jmemansi.c is excluded from build :

if(ANDROID OR IOS)
  ocv_list_filterout(lib_srcs jmemansi.c)
else()
  ocv_list_filterout(lib_srcs jmemnobs.c)
endif()

However, in world module build, the corresponding object file is not excluded from linker input. This can be fixed by filtering out jmemansi.o from linker input :

modules/world/CMakeLists.txt:84

macro(ios_include_3party_libs)
  foreach(l ${ARGN})
    add_dependencies(${the_module} ${l})
    string(REGEX REPLACE "<MODULE_NAME>" "${l}" objpath1 "${CMAKE_BINARY_DIR}/3rdparty/${l}/${objpath0}")
    file(GLOB sources ${CMAKE_SOURCE_DIR}/3rdparty/${l}/*.c)
    foreach(srcname ${sources})
      if(IS_ABSOLUTE "${srcname}")
        file(RELATIVE_PATH srcname "${CMAKE_SOURCE_DIR}/3rdparty/${l}" "${srcname}")
      endif()

      string(REPLACE ".." "__" srcname "${srcname}")
      get_filename_component(srcname_we ${srcname} NAME_WE)
      string(REGEX REPLACE <SRC_NAME_WE> "${srcname_we}" objpath2 "${objpath1}")
      string(REGEX REPLACE <RELATIVE_SRC_NAME> "${srcname}" objpath3 "${objpath2}")

      list(APPEND objlist "\"${objpath3}\"")
    endforeach() # (srcname ${sources})
  endforeach()
  ocv_list_filterout(objlist jmemansi) # <<= dirty fix
endmacro()

Answer 2

Instead of using terminal commands given in the opencv installation guide in official website, use the following commands. Worked for me.

cd OpenCV-2.3.1

mkdir build

cd build

cmake -G "Unix Makefiles" ..

make

sudo make install