OpenCV4Android释疑:透析Android以JNI调OpenCV的三种方式(让OpenCVManager永不困扰)

仰天大笑出门去，我辈岂是蓬蒿人。这篇文章主要讲述OpenCV4Android释疑:透析Android以JNI调OpenCV的三种方式(让OpenCVManager永不困扰)相关的知识，希望能为你提供帮助。
前文曾具体探讨了关于OpenCV的使用，原本以为天下已太平。但不断有人反应依旧配不好OpenCV4android，不能得心应手的在Android上使用OpenCV。大量的精力都浪费在摸索配置上。尤其是OpenCVManager诞生之后。更让人无语。大家第一个反应就是怎样才干不安装OpenCVManager。由于要多安装这个东西对客户来说体验太不好了。
【OpenCV4Android释疑:透析Android以JNI调OpenCV的三种方式(让OpenCVManager永不困扰)】咱家昨夜研究至两点，今早七点起床。最终把头绪理清了。
以下咱家以之前做过的一个基于OpenCV2.3.1。android通过jni调用opencv实现人脸检測的实例来逐个回答，怎样在Android上使用java接口而不安装OpenCVManager,及通过jni方式使用OpenCV的三种方式。

先来看JNI调OpenCV的三种方式。非常多人会惊讶肿么JNI调OpenCV还会有3种方式。长久以来大量网上教程都说在Android上仅仅有Java和JNI两种方式使用OpenCV，怎么又冒出来3种使用JNI的方式。
经本人研究。确实有3种调JNI的方式，就连官网指导文档都模棱两可，所以让非常多人不知所措。
这三种方式各自是:
1、使用静态的OpenCV库的方式。
2、使用动态的OpenCV库的方式;
3、同一时候使用Java的API又使用JNI的接口的方式，此时编译时一般使用的是动态链接OpenCV库的方式。

要说明的是，这三种方式均无需安装OpenCVManager，差别在于mk文件的不同。个人最推崇的就是第一种方式，第一种方式也是和OpenCV2.3.1在JNI调OpenCV使用全然吻合的一种方式。本文是以windows平台最新的OpenCV-2.4.9-android-sdk为基础，使用2.4.9的OpenCV4Android须要使用NDK版本号为r9，本人使用的是android-ndk-r9d的版本号。之所以昨晚捣腾到2点，就是由于之前使用的ndk r7的版本号。怎么编都编只是，因少东西报上千行错误。android-ndk-r9d安装十分简单，仅仅须要解压缩配置一个环境变量就可以。

一、Android以JNI调OpenCV的第一种配置方法:Application.mk文件中的内容例如以下:

APP_STL:=gnustl_static
APP_CPPFLAGS:=-frtti -fexceptions
APP_ABI:= armeabi-v7a

这三种方式的Application.mk都一样，所以往后不说了。在Application.mk里还能够配置APP_PLATFORM=17相似这样的，当然不配置全然能够。

Android.mk内容例如以下:

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

OpenCV_INSTALL_MODULES:=on
OPENCV_CAMERA_MODULES:=off

OPENCV_LIB_TYPE:=STATIC

ifeq ("$(wildcard $(OPENCV_MK_PATH))","")
include D:\ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\OpenCV.mk
else
include $(OPENCV_MK_PATH)
endif

LOCAL_MODULE := ProcessImg
LOCAL_SRC_FILES := DetectFace_JNI.cpp \
src/copyToAssets.cpp \
src/detectFace.cpp
LOCAL_LDLIBS += -lm -llog

include $(BUILD_SHARED_LIBRARY)

逐一解释下，OpenCV_INSTALL_MODULES:=on的意思是自己主动将依赖的OpenCV的so库复制到libs目录下，但非常遗憾的是，这个命令仅仅对OPENCV_CAMERA_MODULES有效。
仅仅有当OPENCV_CAMERA_MODULES:=on时。能够看到他会自己主动将里面的带camera的so拷贝至project下的libs目录下。include D:\ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\OpenCV.mk这句话比較关键，这是我安装OpenCV-2.4.9-android-sdk的地方。我将其安装到了D盘。而我的工作空间在E盘也是ok的。
而不用像OpenCV2.3.1使用时，限制这个解压缩包的位置了。
LOCAL_MODULE 是要生成的库的名字，LOCAL_SRC_FILES 是jni目录下的cpp文件。当中的src说明我的jni下还有个子目录名字是“src”，这块替换成自己的源代码文件就ok了。
为了測试的严谨性。在project里将libs目录的东西。和obj目录下的东西全删了。用cygwin进到project，输入ndk-build，看到例如以下信息:

[email protected] /cygdrive/e/WorkSpaces/OpenCV4Android/FaceDetectLiu2 $ ndk-build Android NDK: WARNING: APP_PLATFORM android-19 is larger than android:minSdkVersion 16 in ./AndroidManifest.xml [armeabi-v7a] Cygwin: Generating dependency file converter script [armeabi-v7a] Compile++ thumb: ProcessImg < = DetectFace_JNI.cpp jni/DetectFace_JNI.cpp: In function ‘_jstring* Java_org_yan_processlib_LibProcessImg_processIplImg(JNIEnv*, jobject, jintArray, int, int)‘: jni/DetectFace_JNI.cpp:99:44: warning: converting ‘false‘ to pointer type for argument 2 of ‘jint* _JNIEnv::GetIntArrayElements(jintArray, jboolean*)‘ [-Wconversion-null] jni/DetectFace_JNI.cpp: In function ‘_jstring* Java_org_yan_processlib_LibProcessImg_processStaticImg(JNIEnv*, jobject, jintArray, int, int)‘: jni/DetectFace_JNI.cpp:133:44: warning: converting ‘false‘ to pointer type for argument 2 of ‘jint* _JNIEnv::GetIntArrayElements(jintArray, jboolean*)‘ [-Wconversion-null] [armeabi-v7a] Compile++ thumb: ProcessImg < = copyToAssets.cpp [armeabi-v7a] Compile++ thumb: ProcessImg < = detectFace.cpp [armeabi-v7a] SharedLibrary: libProcessImg.so [armeabi-v7a] Install: libProcessImg.so => libs/armeabi-v7a/libProcessImg.so

上面两个警告么有关系，编译成功。生成的libProcessImg.so的大小为4M,整个apk大小为1.99M。
注意，假设将mk里的LOCAL_LDLIBS += -lm -llog这一句错误的写为:LOCAL_LDLIBS := -lm -llog。即将“+=”错写成了“：=”将会看到例如以下大量错误:

$ ndk-build Android NDK: WARNING: APP_PLATFORM android-19 is larger than android:minSdkVersion 16 in ./AndroidManifest.xml [armeabi-v7a] Compile++ thumb: ProcessImg < = DetectFace_JNI.cpp jni/DetectFace_JNI.cpp: In function ‘_jstring* Java_org_yan_processlib_LibProcessImg_processIplImg(JNIEnv*, jobject, jintArray, int, int)‘: jni/DetectFace_JNI.cpp:99:44: warning: converting ‘false‘ to pointer type for argument 2 of ‘jint* _JNIEnv::GetIntArrayElements(jintArray, jboolean*)‘ [-Wconversion-null] jni/DetectFace_JNI.cpp: In function ‘_jstring* Java_org_yan_processlib_LibProcessImg_processStaticImg(JNIEnv*, jobject, jintArray, int, int)‘: jni/DetectFace_JNI.cpp:133:44: warning: converting ‘false‘ to pointer type for argument 2 of ‘jint* _JNIEnv::GetIntArrayElements(jintArray, jboolean*)‘ [-Wconversion-null] [armeabi-v7a] Compile++ thumb: ProcessImg < = copyToAssets.cpp [armeabi-v7a] Compile++ thumb: ProcessImg < = detectFace.cpp [armeabi-v7a] SharedLibrary: libProcessImg.so D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function icvGets(CvFileStorage*, char*, int):persistence.cpp(.text._ZL7icvGetsP13CvFileStoragePci+0x7e): error: undefined reference to ‘gzgets‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function icvXMLSkipSpaces(CvFileStorage*, char*, int):persistence.cpp(.text._ZL16icvXMLSkipSpacesP13CvFileStoragePci+0x1c4): error: undefined reference to ‘gzeof‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function icvYMLSkipSpaces(CvFileStorage*, char*, int, int) [clone .constprop.65]:persistence.cpp(.text._ZL16icvYMLSkipSpacesP13CvFileStoragePcii.constprop.65+0x122): error: undefined reference to ‘gzeof‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function icvPuts(CvFileStorage*, char const*):persistence.cpp(.text._ZL7icvPutsP13CvFileStoragePKc+0x32): error: undefined reference to ‘gzputs‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function icvClose(CvFileStorage*, std::string*):persistence.cpp(.text._ZL8icvCloseP13CvFileStoragePSs+0x132): error: undefined reference to ‘gzclose‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function cvOpenFileStorage:persistence.cpp(.text.cvOpenFileStorage+0x1ac): error: undefined reference to ‘gzrewind‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function cvOpenFileStorage:persistence.cpp(.text.cvOpenFileStorage+0x6d4): error: undefined reference to ‘gzclose‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function cvOpenFileStorage:persistence.cpp(.text.cvOpenFileStorage+0x75a): error: undefined reference to ‘gzopen‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../libs/armeabi-v7a/libopencv_core.a(persistence.cpp.o): in function cvOpenFileStorage:persistence.cpp(.text.cvOpenFileStorage+0xd80): error: undefined reference to ‘gzclose‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../3rdparty/libs/armeabi-v7a/liblibpng.a(pngread.c.o): in function png_create_read_struct_2:pngread.c(.text.png_create_read_struct_2+0x112): error: undefined reference to ‘inflateInit_‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../3rdparty/libs/armeabi-v7a/liblibpng.a(pngread.c.o): in function png_read_row:pngread.c(.text.png_read_row+0x218): error: undefined reference to ‘inflate‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../3rdparty/libs/armeabi-v7a/liblibpng.a(pngread.c.o): in function png_read_destroy:pngread.c(.text.png_read_destroy+0x96): error: undefined reference to ‘inflateEnd‘ D:/ProgramFile/android-ndk-r9d/toolchains/arm-linux-androideabi-4.6/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.6/../../../../arm-linux-androideabi/bin/ld.exe: D:/ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\/../3rdparty/libs/armeabi-v7a/liblibpng.a(pngwrite.c.o): in function png_write_flush:pngwrite.c(.text.png_write_flush+0x1c): error: undefined reference to ‘deflate‘

上两张执行效果图,各自是预览界面检測人脸和拍照后检測:

OpenCV4Android释疑:透析Android以JNI调OpenCV的三种方式(让OpenCVManager永不困扰)

文章图片

文章图片

二、Android以JNI调OpenCV的另外一种配置方法
Application.mk文件同上。Android.mk文件例如以下：
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)

OpenCV_INSTALL_MODULES:=on
OPENCV_CAMERA_MODULES:=off
OPENCV_LIB_TYPE:=SHARE
ifeq ("$(wildcard $(OPENCV_MK_PATH))","")
include D:\ProgramFile\OpenCV-2.4.9-android-sdk\sdk\native\jni\OpenCV.mk
else
include $(OPENCV_MK_PATH)
endif

LOCAL_MODULE := ProcessImg
LOCAL_SRC_FILES := DetectFace_JNI.cpp \
src/copyToAssets.cpp \
src/detectFace.cpp
LOCAL_LDLIBS := -lm -llog