android下libjpg.a的编译

在android系统中libjpg默认是动态库.so形式的，在很多需要移植的工程中需要静态的libjpg.a，这就需要先移植libjpg，方法如下：

1：下载libjpg源码

http://ijg.org/files/jpegsrc.v6b.tar.gz
2：放到external\libjpg\下解压

新建Android.mk文件内容如下：

LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)

LOCAL_ARM_MODE := arm

# Set ANDROID_JPEG_USE_VENUM to true to enable VeNum optimizations

# Disable VeNum optimizations if they are not supported on the build target
ifneq ($(ARCH_ARM_HAVE_VFP),true)
ANDROID_JPEG_USE_VENUM := false
else
ifneq ($(ARCH_ARM_HAVE_NEON),true)
ANDROID_JPEG_USE_VENUM := false
endif
endif

LOCAL_SRC_FILES := \
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 jmemansi.c
# the original android memory manager.
# use sdcard as libjpeg decoder's backing store
#LOCAL_SRC_FILES += \
#	jmem-android.c

ifeq ($(ANDROID_JPEG_USE_VENUM),true)
LOCAL_SRC_FILES += jidctvenum.c
LOCAL_SRC_FILES += asm/armv7/jdcolor-armv7.S
LOCAL_SRC_FILES += asm/armv7/jdcolor-android-armv7.S
LOCAL_SRC_FILES += asm/armv7/jdidct-armv7.S
LOCAL_CFLAGS    += -DANDROID_JPEG_USE_VENUM
else # ANDROID_JPEG_USE_VENUM, false
LOCAL_SRC_FILES += jidctint.c jidctfst.c jidctred.c
endif # ANDROID_JPEG_USE_VENUM

LOCAL_CFLAGS += -DAVOID_TABLES
LOCAL_CFLAGS += -O3 -fstrict-aliasing -fprefetch-loop-arrays

# enable tile based decode
LOCAL_CFLAGS += -DANDROID_TILE_BASED_DECODE

# enable armv6 idct assembly
LOCAL_CFLAGS += -DANDROID_ARMV6_IDCT

LOCAL_MODULE:= libjpeg

include $(BUILD_STATIC_LIBRARY)

环境设好后就可以编译出：

target StaticLib: libjpeg (out/target/product/。。。/obj/STATIC_LIBRARIES/libjpeg_intermediates/libjpeg.a)