最近解码视频生成的是yuv数据，然后需要生成jpg图片，之前的方案是yuv-rgb-bmp-jpg这样的话是很慢的，计算了时间大概要300ms左右，导致多次点击照相，会造成视频画面的延迟，所以只能使用别的方案替代，在网上查询libjpeg，但是又看了一篇文章http://www.linuxsir.org/bbs/thread374093.html说libjpeg-turbo比libjpeg快了2-3倍时间，所以打算使用libjpg-turbo来实现yuv转换为jpg图像。下面是使用ndk来交叉编译libjpeg-turbo生成libjpeg-turbo.so。

1、从官网下载最新的libjpeg-turbo源码，http://sourceforge.net/projects/libjpeg-turbo/ ，现在最新的版本是libjpeg-turbo-1.2.1

2、解压缩下载的文件，然后进入，并创建jni文件夹，最后将里面的文件都拷贝到jni文件中

3、进入jni目录，然后创建配置文件(例如jconfig.h，config.h)，在终端输入：

./configure --with-jpeg8

就会生成

config.status: creating config.h

config.status: creating jconfig.h4、接下来是创建Android.mk文件

# Makefile for libjpeg-turbo

##################################################

### simd ###

##################################################

LOCAL_PATH := $(my-dir)

include $(CLEAR_VARS)

LOCAL_CFLAGS += -D__ARM_HAVE_NEON

# From autoconf-generated Makefile

EXTRA_DIST = simd/nasm_lt.sh simd/jcclrmmx.asm simd/jcclrss2.asm simd/jdclrmmx.asm simd/jdclrss2.asm \

simd/jdmrgmmx.asm simd/jdmrgss2.asm simd/jcclrss2-64.asm simd/jdclrss2-64.asm \

simd/jdmrgss2-64.asm simd/CMakeLists.txt

libsimd_SOURCES_DIST = simd/jsimd_arm_neon.S \

simd/jsimd_arm.c

LOCAL_SRC_FILES := $(libsimd_SOURCES_DIST)

LOCAL_C_INCLUDES := $(LOCAL_PATH)/simd \

$(LOCAL_PATH)/android

AM_CFLAGS := -march=armv7-a -mfpu=neon

AM_CCASFLAGS := -march=armv7-a -mfpu=neon

LOCAL_ARM_MODE=arm

LOCAL_MODULE_TAGS := debug

LOCAL_MODULE := libsimd

include $(BUILD_STATIC_LIBRARY)

######################################################

### libjpeg.so ##

######################################################

include $(CLEAR_VARS)

# From autoconf-generated Makefile

libjpeg_SOURCES_DIST = jcapimin.c jcapistd.c jccoefct.c jccolor.c \

jcdctmgr.c jchuff.c jcinit.c jcmainct.c jcmarker.c jcmaster.c \

jcomapi.c jcparam.c jcphuff.c jcprepct.c jcsample.c jctrans.c \

jdapimin.c jdapistd.c jdatadst.c jdatasrc.c jdcoefct.c jdcolor.c \

jddctmgr.c jdhuff.c jdinput.c jdmainct.c jdmarker.c jdmaster.c \

jdmerge.c jdphuff.c jdpostct.c jdsample.c jdtrans.c jerror.c \

jfdctflt.c jfdctfst.c jfdctint.c jidctflt.c jidctfst.c jidctint.c \

jidctred.c jquant1.c jquant2.c jutils.c jmemmgr.c jmemnobs.c \

jaricom.c jcarith.c jdarith.c \

turbojpeg.c transupp.c jdatadst-tj.c jdatasrc-tj.c \

turbojpeg-mapfile

LOCAL_SRC_FILES:= $(libjpeg_SOURCES_DIST)

LOCAL_SHARED_LIBRARIES := libcutils

LOCAL_STATIC_LIBRARIES := libsimd

LOCAL_ARM_MODE=arm

LOCAL_C_INCLUDES := $(LOCAL_PATH)

LOCAL_CFLAGS :=-O3 -fstrict-aliasing -fprefetch-loop-arrays -DANDROID \

-DANDROID_TILE_BASED_DECODE -DENABLE_ANDROID_NULL_CONVERT -D__ARM_HAVE_NEON

AM_CFLAGS := -march=armv7-a -mfpu=neon

AM_CCASFLAGS := -march=armv7-a -mfpu=neon

LOCAL_MODULE_PATH := $(TARGET_OUT_OPTIONAL_STATIC_LIBRARY)

LOCAL_MODULE_TAGS := debug

LOCAL_MODULE := libjpeg

include $(BUILD_SHARED_LIBRARY)

5、然后在终端输入ndk-build，结果如下：

root@zhangjie:/home/libjpeg-turbo-1.2.1/jni# ndk-build

Android NDK: WARNING: Unsupported source file extensions in /home/libjpeg-turbo-1.2.1/jni/Android.mk for module jpeg

Android NDK: turbojpeg-mapfile

Compile arm : jpeg <= jcapimin.c

Compile arm : jpeg <= jcapistd.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 <= jcphuff.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 <= 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 <= jdphuff.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 <= jidctred.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

Compile arm : jpeg <= jaricom.c

Compile arm : jpeg <= jcarith.c

Compile arm : jpeg <= jdarith.c

Compile arm : jpeg <= turbojpeg.c

Compile arm : jpeg <= transupp.c

Compile arm : jpeg <= jdatadst-tj.c

Compile arm : jpeg <= jdatasrc-tj.c

Compile arm : simd <= jsimd_arm_neon.S

Compile arm : simd <= jsimd_arm.c

StaticLibrary : libsimd.a

SharedLibrary : libjpeg.so

Install : libjpeg.so => libs/armeabi/libjpeg.so