1. libjpeg-turbo

  前面已經編譯過1.5.9¹版本的libjpeg-turbo,現在版本升級到2.0.1,基於CMake編譯。

  依然還是一樣,按照官網介紹，libjpeg-turbo比libjpeg快2-6倍,得益於它高度優化的哈夫曼演算法。在許多情況下，libjpeg-turbo的效能可與專有的高速JPEG編解碼器相媲美.

On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg, all else being equal. On other types of systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by virtue of its highly-optimized Huffman coding routines. In many cases, the performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs

2. 編譯過程

2.1 編譯環境

在Windows 10的虛擬機器VM上的Ubuntu中編譯

2.2 編譯要求

我們將參照原始碼中的BUILDING.md編譯，github地址BUILDING.md

2.3 配置環境變數

把Cmake配置進系統環境變數，當然這不是必須的。

2.4 編譯

2.4.1 下載原始碼

2.4.2 編譯指令碼

2.4.2.1 sh編譯指令碼(自定義編譯鏈)

注意

這種方式是完全按照原始碼中的BUILDING.md構建，稍顯複雜，容易出錯。但是不要求CMake的交叉編譯工具鏈，也就是說，我們隨便在CMake官網下載Linux版本就可以用了。

#!/bin/sh
 


# lib-name
MY_LIBS_NAME=libjpeg-turbo
MY_SOURCE_DIR=$(pwd)/libjpeg-turbo-master
#編譯的過程中產生的中介軟體的存放目錄，為了區分編譯目錄，原始碼目錄，install目錄
MY_BUILD_DIR=binary

export PATH=/home/as/Android/cmake-3.12.1-Linux-x86_64/bin:$PATH

NDK_PATH=/home/as/Android/android-ndk-r15c
BUILD_PLATFORM=linux-x86_64
TOOLCHAIN_VERSION=4.9
ANDROID_VERSION=
 
24

ANDROID_ARMV5_CFLAGS="-march=armv5te"
ANDROID_ARMV7_CFLAGS="-march=armv7-a -mfloat-abi=softfp -mfpu=neon"  # -mfpu=vfpv3-d16  -fexceptions -frtti
ANDROID_ARMV8_CFLAGS="-march=armv8-a"  	# -mfloat-abi=softfp -mfpu=neon -fexceptions -frtti
ANDROID_X86_CFLAGS="-march=i386 -mtune=intel -mssse3 -mfpmath=sse -m32"
ANDROID_X86_64_CFLAGS="-march=x86-64 -msse4.2 -mpopcnt -m64 -mtune=intel"

# params($1:arch,$2:arch_abi,$3:host,$4:compiler,$5:cflags,$6:processor)
build_bin() {

    echo "-------------------star build $2-------------------------"

    ARCH=$1                # arm arm64 x86 x86_64
    ANDROID_ARCH_ABI=$2    # armeabi armeabi-v7a x86 mips
    # 最終編譯的安裝目錄
    PREFIX=$(pwd)/dist/${MY_LIBS_NAME}/${ANDROID_ARCH_ABI}/
    HOST=$3
    COMPILER=$4
    PROCESSOR=$6
    SYSROOT=${NDK_PATH}/platforms/android-${ANDROID_VERSION}/arch-${ARCH}
    CFALGS="$5"
    TOOLCHAIN=${NDK_PATH}/toolchains/${HOST}-${TOOLCHAIN_VERSION}/prebuilt/${BUILD_PLATFORM}
    
    # build 中介軟體
    BUILD_DIR=./${MY_BUILD_DIR}/${ANDROID_ARCH_ABI}

    export CFLAGS="$5 -Os -D__ANDROID_API__=${ANDROID_VERSION} --sysroot=${SYSROOT} \
                   -isystem ${NDK_PATH}/sysroot/usr/include \
                   -isystem ${NDK_PATH}/sysroot/usr/include/${HOST} "
    export LDFLAGS=-pie

    echo "path==>$PATH"
    echo "build_dir==>$BUILD_DIR"
    echo "ARCH==>$ARCH"
    echo "ANDROID_ARCH_ABI==>$ANDROID_ARCH_ABI"
    echo "HOST==>$HOST"
    echo "CFALGS==>$CFALGS"
    echo "COMPILER==>$COMPILER-gcc"
    echo "PROCESSOR==>$PROCESSOR"

    mkdir -p ${BUILD_DIR}   #建立當前arch_abi的編譯目錄,比如:binary/armeabi-v7a
    cd ${BUILD_DIR}         #此處 進了當前arch_abi的2級編譯目錄


cat >toolchain.cmake << EOF 
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR $6)
set(CMAKE_C_COMPILER ${TOOLCHAIN}/bin/${COMPILER}-gcc)
set(CMAKE_FIND_ROOT_PATH ${TOOLCHAIN}/${COMPILER})
EOF # 此處不頂格寫指令碼會報一個錯誤

    cmake -G"Unix Makefiles" \
          -DCMAKE_TOOLCHAIN_FILE=toolchain.cmake \
          -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
          -DCMAKE_INSTALL_PREFIX=${PREFIX} \
          -DWITH_JPEG8=1 \
          ${MY_SOURCE_DIR}

    make clean
    make
    make install

    #從當前arch_abi編譯目錄跳出，對應上面的cd ${BUILD_DIR},以便function多次執行
    cd ../../

    echo "-------------------$2 build end-------------------------"
}

# build armeabi
build_bin arm armeabi arm-linux-androideabi arm-linux-androideabi "$ANDROID_ARMV5_CFLAGS" arm

#build armeabi-v7a
build_bin arm armeabi-v7a arm-linux-androideabi arm-linux-androideabi "$ANDROID_ARMV7_CFLAGS" arm

#build arm64-v8a
build_bin arm64 arm64-v8a aarch64-linux-android aarch64-linux-android "$ANDROID_ARMV8_CFLAGS" aarch64

#build x86
build_bin x86 x86 x86 i686-linux-android "$ANDROID_X86_CFLAGS" i386

#build x86_64
build_bin x86_64 x86_64 x86_64 x86_64-linux-android "$ANDROID_X86_64_CFLAGS" x86_64

2.4.2.2 android-cmake(自帶編譯鏈)

注意

這個指令碼要求Linux環境的Android-cmake，通過Android sdk-manager下載更新cmake，android-cmake已經自帶交叉編譯工具鏈，但通常我們不使用cmake帶的，因為他腳本里寫死了NDK版本12，而NDK的build/cmake目錄裡也帶了相應的編譯鏈，所以，我們一般使用我們NDK自帶的編譯鏈。

# lib-name
MY_LIBS_NAME=libjpeg-turbo
MY_SOURCE_DIR=$(pwd)/libjpeg-turbo-master
MY_BUILD_DIR=binary

CMAKE_PATH=/home/as/Android/cmake-3.6.4111459-linux-x86_64

export PATH=${CMAKE_PATH}/bin:$PATH

NDK_PATH=/home/as/Android/android-ndk-r15c
BUILD_PLATFORM=linux-x86_64
TOOLCHAIN_VERSION=4.9
ANDROID_VERSION=24

ANDROID_ARMV5_CFLAGS="-march=armv5te"
ANDROID_ARMV7_CFLAGS="-march=armv7-a -mfloat-abi=softfp -mfpu=neon"  # -mfpu=vfpv3-d16  -fexceptions -frtti
ANDROID_ARMV8_CFLAGS="-march=armv8-a "  			     # -mfloat-abi=softfp -mfpu=neon -fexceptions -frtti
ANDROID_X86_CFLAGS="-march=i386 -mtune=intel -mssse3 -mfpmath=sse -m32"
ANDROID_X86_64_CFLAGS="-march=x86-64 -msse4.2 -mpopcnt -m64 -mtune=intel"

# params($1:arch,$2:arch_abi,$3:host,$4:compiler,$5:cflags,$6:processor)
build_bin() {

    echo "-------------------start build $1-------------------------"

    ANDROID_ARCH_ABI=$1    # armeabi armeabi-v7a x86 mips
    CFALGS="$2"
    
    PREFIX=$(pwd)/dist/${MY_LIBS_NAME}/${ANDROID_ARCH_ABI}/
    # build 中介軟體
    BUILD_DIR=./${MY_BUILD_DIR}/${MY_LIBS_NAME}/${ANDROID_ARCH_ABI}

    echo "path==>$PATH"
    echo "build_dir==>$BUILD_DIR"
    echo "ANDROID_ARCH_ABI==>$ANDROID_ARCH_ABI"
    echo "CFALGS==>$CFALGS"


    mkdir -p ${BUILD_DIR}
    cd ${BUILD_DIR}

    # -DCMAKE_MAKE_PROGRAM=${NDK_PATH}/prebuilt/${BUILD_PLATFORM}/bin/make \
    # -DCMAKE_ASM_COMPILER=${NDK_PATH}/prebuilt/${BUILD_PLATFORM}/bin/yasm \

    cmake -G"Unix Makefiles" \
      -DANDROID_ABI=${ANDROID_ARCH_ABI} \
      -DANDROID_PLATFORM=android-${ANDROID_VERSION} \
      -DCMAKE_BUILD_TYPE=Release \
      -DANDROID_NDK=${NDK_PATH} \
      -DCMAKE_TOOLCHAIN_FILE=${NDK_PATH}/build/cmake/android.toolchain.cmake \
      -DCMAKE_POSITION_INDEPENDENT_CODE=1 \
      -DCMAKE_INSTALL_PREFIX=${PREFIX} \
      -DANDROID_ARM_NEON=TRUE \
      -DANDROID_TOOLCHAIN=clang \
      -DANDROID_STL=c++_static \
      -DCMAKE_C_FLAGS="${CFALGS} -Os -Wall -pipe -fPIC" \
      -DCMAKE_CXX_FLAGS="${CFALGS} -Os -Wall -pipe -fPIC" \
      -DANDROID_CPP_FEATURES=rtti exceptions \
      -DWITH_JPEG8=1 \
      ${MY_SOURCE_DIR}

    make clean
    make
    make install

    cd ../../../

    echo "-------------------$1 build end-------------------------"
}

# build armeabi
build_bin armeabi "$ANDROID_ARMV5_CFLAGS"

#build armeabi-v7a
build_bin armeabi-v7a "$ANDROID_ARMV7_CFLAGS"

#build arm64-v8a
build_bin arm64-v8a "$ANDROID_ARMV8_CFLAGS"

#build x86
build_bin x86 "$ANDROID_X86_CFLAGS"

#build x86_64
build_bin x86_64 "$ANDROID_X86_64_CFLAGS"

2.4.3 去掉版本號

動態庫的版本號
  安裝規則一般so都會帶版本號，但是如果我們在Android上使用不帶版本號。可以通過修改CMake指令碼，不帶版本號。

動態庫實現版本號一般使用SET_TARGET_PROPERTIES指令定義一下語句:
  SET_TARGET_PROPERTIES(target PROPERTIES VERSION 1.2 SOVERSION 1)
VERSION 指代動態庫版本，SOVERSION 指代 API 版本

1. libjpeg-turbo-master/CMakeLists.txt中註釋
   
2. libjpeg-turbo-master/sharedlib/CMakeLists.txt中註釋
   

2.4.4 執行編譯指令碼

sh build.sh

註釋版本號編譯

註釋版本號

2.4.5 編譯可能遇到的問題

1.Syntax error: end of file unexpected (expecting "}")

編譯指令碼中 cat <<EOF >檔名 內容 EOF,最好頂格寫，否則可能出現上述錯誤

2.未識別的cflags引數

一些cflags引數可能導致編譯識別,修改編譯出錯的引數即可

2.4.6 install結果

註釋了版本號