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.h

# 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)