android 编译libjpeg

       之前需要将yuv转换为jpg图像，查看网上说libjpeg-turbo比libjpeg快2-3倍，但是在android手机上实践了一下，需要40-60个ms，这个虽然比以前的300ms好多了，但是还是不能满足我的要求，进一步查看了网上信息，libjpeg-turbo是为x86和x86-64进行优化的使用了SIMD指令，而手机上不支持，所以需要在试验一下libjpeg的需要。下面是我的编译步骤：

1、先到官网上下载源码http://www.ijg.org/files/jpegsr9.zip  最新的是jpegsr9

2、然后加压，生成jpeg-9,进入并创建jni目录，将里面的内容都拷贝到jni里面

3、生成配置文件，在jni目录下面创建config.sh文件，然后在里面添加：

NDK=/opt/android-ndk-r8d
PLATFORM=$NDK/platforms/android-8/arch-arm/
PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
CC=$PREBUILT/bin/arm-linux-androideabi-gcc
./configure --prefix=/home/jpeg-9/jni/dist --host=arm CC="$CC --sysroot=$PLATFORM"

4、然后改变config.sh的权限，并执行,得到配置文件：

chmod 775 config.sh
sh config.sh

5、生成Android.mk文件，内容如下：

LOCAL_PATH := $(my-dir)

include $(CLEAR_VARS)
# From autoconf-generated Makefile
LOCAL_MODULE := libjpeg
LOCAL_ARM_MODE=arm
LOCAL_SRC_FILES := \
		   jaricom.c \
		   jcapimin.c \
		   jcapistd.c \
		   jcarith.c \
		   jccoefct.c \
		   jccolor.c \
		   jcdctmgr.c \
		   jchuff.c \
		   jcinit.c \
		   jcmainct.c \
		   jcmarker.c \
		   jcmaster.c \
		   jcomapi.c \
		   jcparam.c \
		   jcprepct.c \
		   jcsample.c \
		   jctrans.c \
		   jdapimin.c \
		   jdapistd.c \
		   jdarith.c \
		   jdatadst.c \
		   jdatasrc.c \
		   jdcoefct.c \
		   jdcolor.c \
		   jddctmgr.c \
		   jdhuff.c \
		   jdinput.c \
		   jdmainct.c \
		   jdmarker.c \
		   jdmaster.c \
		   jdmerge.c \
		   jdpostct.c \
		   jdsample.c \
		   jdtrans.c \
		   jerror.c \
		   jfdctflt.c \
		   jfdctfst.c \
		   jfdctint.c \
		   jidctflt.c \
		   jidctfst.c \
		   jidctint.c \
		   jquant1.c \
		   jquant2.c \
		   jutils.c \
		   jmemmgr.c \
		   jmemnobs.c
LOCAL_C_INCLUDES := $(LOCAL_PATH)
LOCAL_CFLAGS :=-O3 -fstrict-aliasing -fprefetch-loop-arrays  -DANDROID \
        -DANDROID_TILE_BASED_DECODE -DENABLE_ANDROID_NULL_CONVERT

include $(BUILD_SHARED_LIBRARY)

6、运行ndk-build,结果如下：

root@zhangjie:/home/jpeg-9/jni# ndk-build
Compile arm    : jpeg <= jaricom.c
Compile arm    : jpeg <= jcapimin.c
Compile arm    : jpeg <= jcapistd.c
Compile arm    : jpeg <= jcarith.c
Compile arm    : jpeg <= jccoefct.c
Compile arm    : jpeg <= jccolor.c
Compile arm    : jpeg <= jcdctmgr.c
Compile arm    : jpeg <= jchuff.c
Compile arm    : jpeg <= jcinit.c
Compile arm    : jpeg <= jcmainct.c
Compile arm    : jpeg <= jcmarker.c
Compile arm    : jpeg <= jcmaster.c
Compile arm    : jpeg <= jcomapi.c
Compile arm    : jpeg <= jcparam.c
Compile arm    : jpeg <= jcprepct.c
Compile arm    : jpeg <= jcsample.c
Compile arm    : jpeg <= jctrans.c
Compile arm    : jpeg <= jdapimin.c
Compile arm    : jpeg <= jdapistd.c
Compile arm    : jpeg <= jdarith.c
Compile arm    : jpeg <= jdatadst.c
Compile arm    : jpeg <= jdatasrc.c
Compile arm    : jpeg <= jdcoefct.c
Compile arm    : jpeg <= jdcolor.c
Compile arm    : jpeg <= jddctmgr.c
Compile arm    : jpeg <= jdhuff.c
Compile arm    : jpeg <= jdinput.c
Compile arm    : jpeg <= jdmainct.c
Compile arm    : jpeg <= jdmarker.c
Compile arm    : jpeg <= jdmaster.c
Compile arm    : jpeg <= jdmerge.c
Compile arm    : jpeg <= jdpostct.c
Compile arm    : jpeg <= jdsample.c
Compile arm    : jpeg <= jdtrans.c
Compile arm    : jpeg <= jerror.c
Compile arm    : jpeg <= jfdctflt.c
Compile arm    : jpeg <= jfdctfst.c
Compile arm    : jpeg <= jfdctint.c
Compile arm    : jpeg <= jidctflt.c
Compile arm    : jpeg <= jidctfst.c
Compile arm    : jpeg <= jidctint.c
Compile arm    : jpeg <= jquant1.c
Compile arm    : jpeg <= jquant2.c
Compile arm    : jpeg <= jutils.c
Compile arm    : jpeg <= jmemmgr.c
Compile arm    : jpeg <= jmemnobs.c
SharedLibrary  : libjpeg.so
Install        : libjpeg.so => libs/armeabi/libjpeg.so

7、由于我只想要编码所以精简了代码，将编译出的库只包含编码，不包含解码库，下面的代码如下，只需要替换Android.mk文件相同部分就可以：

LOCAL_SRC_FILES := jniffmpeg/AppDecodeH264.c \
                   jniffmpeg/yuv420rgb565.s \
                   jniffmpeg/yuv2jpg.c \
                   jpeg-9/jaricom.c \
                   jpeg-9/jcapimin.c \
                   jpeg-9/jcapistd.c \
                   jpeg-9/jcarith.c \
                   jpeg-9/jccoefct.c \
                   jpeg-9/jccolor.c \
                   jpeg-9/jcdctmgr.c \
                   jpeg-9/jchuff.c \
                   jpeg-9/jcinit.c \
                   jpeg-9/jcmainct.c \
                   jpeg-9/jcmarker.c \
                   jpeg-9/jcmaster.c \
                   jpeg-9/jcomapi.c \
                   jpeg-9/jcparam.c \
                   jpeg-9/jcprepct.c \
                   jpeg-9/jcsample.c \
                   jpeg-9/jctrans.c \
                   jpeg-9/jdatadst.c \   
                   jpeg-9/jerror.c \
                   jpeg-9/jfdctflt.c \
                   jpeg-9/jfdctfst.c \
                   jpeg-9/jfdctint.c \
                   jpeg-9/jidctflt.c \
                   jpeg-9/jidctfst.c \
                   jpeg-9/jidctint.c \
                   jpeg-9/jquant1.c \
                   jpeg-9/jquant2.c \
                   jpeg-9/jutils.c \
                   jpeg-9/jmemmgr.c \
                   jpeg-9/jmemnobs.c