Android Studio： JNI 使用小結

項目描述：在Android上部署KCF跟蹤算法，KCF 源碼為c++，且依賴OpenCV，為友善使用，在Android studio中将KCF打包成JNI類。實作過程涉及： JNI 調用 C++ 類對象/方法傳遞數組，c++ java Opencv 混合使用， cv::Mat和Bitmap的轉換等。

1. 添加OpenCV依賴

Android OpenCV document: https://docs.opencv.org/2.4/doc/tutorials/introduction/android_binary_package/dev_with_OCV_on_Android.html#application-development-with-static-initialization
下載下傳 OpenCV-android-sdk ，在項目中： file -> new -> import module ,選擇 your_path/OpenCV-android-sdk/sdk/java ,導入Android studio 後，module名為 openCVLibrary320

修改

openCVLibrary320

中的

build.gradle

compileSdkVersion   
buildToolsVersion "25.0.3"
minSdkVersion  // 至少是 21 否則opencv camera類報錯
targetSdkVersion

為 app module添加依賴：project視圖中打開 open module settings , 選擇app module ,右邊綠色小加号點選，添加mudle dependence: openCVLibrary320

OpenCV mixedprocessing: C++源碼也依賴opencv，在Android.mk 編譯c++庫的時候要添加opencv依賴，

Android.mk :

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

ifdef OPENCV_ANDROID_SDK
ifneq ("","$(wildcard $(OPENCV_ANDROID_SDK)/OpenCV.mk)")
  include ${OPENCV_ANDROID_SDK}/OpenCV.mk
else
  include ${OPENCV_ANDROID_SDK}/sdk/native/jni/OpenCV.mk
endif
else
include ../../sdk/native/jni/OpenCV.mk
endif

include /home/wurui/project/android/OpenCV-android-sdk/sdk/native/jni/OpenCV.mk

LOCAL_MODULE    := jniKCF

LOCAL_SRC_FILES := ffttools.hpp \
                 fhog.cpp \
                 kcftracker.cpp \
                 labdata.hpp \
                 recttools.hpp \
                 kcfClass.cpp

LOCAL_LDLIBS +=  -llog -ldl \ ## 在JNI中使用LOG
               -lm -llog -ljnigraphics
LOCAL_LDFLAGS += -ljnigraphics ## mat/bitmap convert
include $(BUILD_SHARED_LIBRARY)

Application.mk :

APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions
APP_ABI := armeabi-v7a
APP_PLATFORM := android-8

為Android.mk和cpp檔案添加關聯：

可以從圖形界面添加，也可以從build.gradle添加：

apply plugin: 'com.android.application'

allprojects {
  repositories {
      jcenter()
      flatDir {
          dirs 'libs'
      }
  }
}

android {
  compileSdkVersion 
  buildToolsVersion "25.0.3"
  defaultConfig {
      applicationId "camera.hj.cameracontroller"
      minSdkVersion 
      targetSdkVersion 
      versionCode 
      versionName "1.0"
      testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

      ndk {
          moduleName "jniKCF"
          abiFilters "armeabi-v7a"
      }
  }

  buildTypes {
      release {
          minifyEnabled false
          proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
      }
  }

  sourceSets {
      main {
          assets.srcDirs = ['assets']
          jni.srcDirs = []  //屏蔽gradle的jni生成過程
          jniLibs.srcDirs = ['src/main/jniLibs']
      }
  }
  externalNativeBuild {
      ndkBuild {
          path 'src/main/cpp/Android.mk'  // 指定Android.mk
      }
  }
}
dependencies {
  compile fileTree(include: ['*.jar'], dir: 'libs')
  androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
      exclude group: 'com.android.support', module: 'support-annotations'
  })
  compile 'com.android.support:appcompat-v7:25.0.0'
  compile 'com.jakewharton:butterknife:8.5.1'
  annotationProcessor 'com.jakewharton:butterknife-compiler:8.5.1'
  compile 'com.squareup.retrofit2:retrofit:2.3.0'
  //RxJava and RxAndroid
  compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
  // Because RxAndroid releases are few and far between, it is recommended you also
  // explicitly depend on RxJava's latest version for bug fixes and new features.
  compile 'io.reactivex.rxjava2:rxjava:2.1.0'
  testCompile 'junit:junit:4.12'
  // wrz
  compile(name: 'snpe-release', ext: 'aar')
  compile project(':openCVLibrary320')
}

2. JNI将C++源碼打包

JNI調用C++時，希望保留C++的類對象，通過傳位址實作。建立一個JNI類：jniKCF.java

public class jniKCF {
  // JNI
  static {
      System.loadLibrary("jniKCF");
  }
  //儲存c++類的位址
  long nativeKCF;
  //構造函數
  public jniKCF(){
      this.nativeKCF = createNativeObject();
  }
  /**本地方法：建立c++對象并傳回位址*/
  private native long createNativeObject();

  public native void kcfInit(long kcfAddr, Object bmp, int[] rect);

  public native int[] kcfUpdate(long kcfAddr, Object bmp);

  // Functions
  public void init(Bitmap bitmap, int[] rect){
      kcfInit(this.nativeKCF, bitmap, rect);
  }

  public int[] update(Bitmap bitmap){
      int rect[] = new int[];
      rect = kcfUpdate(this.nativeKCF, bitmap);
      return rect;
  }
}

生成頭檔案：在 Terminal 中：

cd app/src/main/java

然後

javah -jni com.xxx.xxx.jniKCF

,就在java檔案夾下生成了頭檔案。把頭檔案拷貝到 app/src/main/cpp/下重命名為

kcfClass.h

/* DO NOT EDIT THIS FILE - it is machine generated */

#include <jni.h>


#include <string>


#include <opencv2/core.hpp>


#include <opencv2/imgproc.hpp>


#include <opencv2/features2d.hpp>


#include <vector>


#include "test.h"


#include<android/bitmap.h>

/* Header for class com_example_wurui_kcf_ndk_jniKCF */


#ifndef _Included_com_example_wurui_kcf_ndk_jniKCF


#define _Included_com_example_wurui_kcf_ndk_jniKCF


#ifdef __cplusplus

extern "C" {

#endif

/*
* Class:     com_example_wurui_kcf_ndk_jniKCF
* Method:    createNativeObject
* Signature: ()J
*/
JNIEXPORT jlong JNICALL Java_camera_hj_cameracontroller_decoder_jniKCF_createNativeObject
      (JNIEnv *, jobject);

/*
* Class:     camera_hj_cameracontroller_decoder_jniKCF
* Method:    kcfInit
* Signature: (JLjava/lang/Object;[I)V
*/
JNIEXPORT void JNICALL Java_camera_hj_cameracontroller_decoder_jniKCF_kcfInit
      (JNIEnv *, jobject, jlong, jobject, jintArray);

/*
* Class:     camera_hj_cameracontroller_decoder_jniKCF
* Method:    kcfUpdate
* Signature: (JLjava/lang/Object;)[I
*/
JNIEXPORT jintArray JNICALL Java_camera_hj_cameracontroller_decoder_jniKCF_kcfUpdate
      (JNIEnv *, jobject, jlong, jobject);


#ifdef __cplusplus

}

#endif


#endif

實作 kcfClass.cpp :

//
// Created by wurui on 17-12-11.
//


#include "kcfClass.h"


#include "kcftracker.hpp"


#include <android/log.h>


#include "eben_hpc_log.h"


#include <math.h>


using namespace cv;
using namespace std;

JNIEXPORT jlong JNICALL
Java_camera_hj_cameracontroller_decoder_jniKCF_createNativeObject(JNIEnv *env, jobject obj){
  jlong result;

  bool HOG = true;
  bool FIXEDWINDOW = false;
  bool MULTISCALE = false;
  bool LAB = false;
  result = (jlong) new KCFTracker(HOG, FIXEDWINDOW, MULTISCALE, LAB);
  return result;
}

/*
* Class:     com_example_wurui_kcf_ndk_jniKCF
* Method:    kcfInit
* Signature: (Ljava/lang/Object;[I)V
*/
JNIEXPORT void JNICALL Java_camera_hj_cameracontroller_decoder_jniKCF_kcfInit
(JNIEnv *env, jobject obj, jlong kcfClassAddr,jobject jbmp1, jintArray jrect){
  // 擷取圖檔
  AndroidBitmapInfo bmp1info;
  void* bmp1pixels;
  int height,width,ret,y,x;

  if ((ret = AndroidBitmap_getInfo(env, jbmp1, &bmp1info)) < ) {
      return ;
  }

  if (bmp1info.format != ANDROID_BITMAP_FORMAT_RGBA_8888 || bmp1info.format != ANDROID_BITMAP_FORMAT_RGBA_8888) {
      LOGE("Bitmap format is not RGBA_8888!");
      return ;
  }

  if ((ret = AndroidBitmap_lockPixels(env, jbmp1, &bmp1pixels)) < ) {
      LOGE("First Bitmap LockPixels Failed return=%d!", ret);
      return ;
  }

  AndroidBitmap_unlockPixels(env, jbmp1);
  height = bmp1info.height;
  width = bmp1info.width;
  // Bitmap 直接轉換得到的是4通道的 Mat
  cv::Mat image1(height,width,CV_8UC4,bmp1pixels);

  if(!(image1.data )){
      LOGE("before bitmap failed convert to Mat return=%d!", ret);
      LOGD("------------------ CV image CV_8UC4 null ----------------------");
      return ;
  }

  // 為了算法處理，需要得到 BGR 圖像 image1
  cvtColor(image1,image1,CV_RGBA2BGR);
  if(!(image1.data)){
      LOGE("after bitmap failed convert to Mat return=%d!", ret);
      LOGD("------------------ CV image CV_8UC3 null ----------------------");
      return ;
  }

  // 讀取數組 ==== RectBuffer
  int* RectBuffer = new int[]; // result rect
  int* arrayPointer = (*env).GetIntArrayElements(jrect,NULL);
  for(int i=;i<;i++){
      RectBuffer[i] = arrayPointer[i];
  }
  cv::Rect rect = cv::Rect(RectBuffer[], RectBuffer[], RectBuffer[], RectBuffer[]);

  // 初始化 kcf tracker
  // (KCFTracker*)kcfClassAddr 為傳入的C++類對象的指針
  ((KCFTracker*)kcfClassAddr)->init(rect, image1);
  (*env).ReleaseIntArrayElements(jrect,arrayPointer,);
}

/*
* Class:     com_example_wurui_kcf_ndk_jniKCF
* Method:    kcfUpdate
* Signature: (Ljava/lang/Object;)[I
*/
JNIEXPORT jintArray JNICALL Java_camera_hj_cameracontroller_decoder_jniKCF_kcfUpdate
(JNIEnv *env, jobject obj, jlong kcfClassAddr,jobject jbmp1){
  // 擷取圖檔
  AndroidBitmapInfo bmp1info;
  void* bmp1pixels;
  int height,width,ret,y,x;

  if ((ret = AndroidBitmap_getInfo(env, jbmp1, &bmp1info)) < ) {
      return NULL;
  }

  if (bmp1info.format != ANDROID_BITMAP_FORMAT_RGBA_8888 || bmp1info.format != ANDROID_BITMAP_FORMAT_RGBA_8888) {
      LOGE("Bitmap format is not RGBA_8888!");
      return NULL;
  }

  if ((ret = AndroidBitmap_lockPixels(env, jbmp1, &bmp1pixels)) < ) {
      LOGE("First Bitmap LockPixels Failed return=%d!", ret);
      return NULL;
  }

  AndroidBitmap_unlockPixels(env, jbmp1);
  height = bmp1info.height;
  width = bmp1info.width;
  cv::Mat image1(height,width,CV_8UC4,bmp1pixels);

  if(!(image1.data )){
      LOGE("before bitmap failed convert to Mat return=%d!", ret);
      LOGD("------------------ CV image CV_8UC4 null ----------------------");
      return NULL;
  }

  // 得到 BGR 圖像 ==== image1
  cvtColor(image1,image1,CV_RGBA2BGR);
  if(!(image1.data)){
      LOGE("after bitmap failed convert to Mat return=%d!", ret);
      LOGD("------------------ CV image CV_8UC3 null ----------------------");
      return NULL;
  }

  // Update kcf
  cv::Rect rect;
  rect = ((KCFTracker*)kcfClassAddr)->update(image1);

  // 傳回結果 數組
  int resultRect[];
  resultRect[] = rect.x;
  resultRect[] = rect.y;
  resultRect[] = rect.width;
  resultRect[] = rect.height;

  jintArray array =(*env).NewIntArray();
  (*env).SetIntArrayRegion(array,,,resultRect);
  return array;
}

Android Studio： JNI 使用小結Android Studio： JNI 使用小結

Android Studio： JNI 使用小結

1. 添加OpenCV依賴

2. JNI将C++源碼打包

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