ncnn 是腾讯提供的移动端框架 非常适合在手机玩

在研究了一段时间的 ncnn后 准备做一个安卓的demo 以便更好的熟悉和使用 NCNN

app地址 ：https://pan.baidu.com/s/1MX8GnM3xR4u0dcyw7iVSRg  已经失效 从 https://github.com/chentyjpm/MobileNetSSD_Demo_AndroidNCNN/releases/download/new/RealTimeCamSSD_fixCameraDisplayerr.zip
下载吧

程序本身并不复杂 但是搞安卓的过程中发现 摄像头获取下视频真的是累的要去死

    ----------    -----------------                 -------------
    |Main窗口| -->|Camera Fragment|  获取图像 ----> |Surface显示| <--
    ---------- |  -----------------             |   -------------   |
               |                                |                   |
               |  --------------                |   --------------  |
               -->|JNI 加载模型|                --->|ncnn推理计算|---
                  --------------                    --------------

JAVA    
    -----------    ------------------      -------------
    |CAMERAYUV| -->|YUV 转RGB Bitmap|  --> |Surface显示|
    -----------  | ------------------      -------------
                 |                                  |
JNI              | --------------    -----------    | 
                 ->|YUV Y 转 RGB| -->|Mobilenet| -->|
                   --------------    -----------     

    private void requestCameraPermission() {
        if (shouldShowRequestPermissionRationale(Manifest.permission.CAMERA)) {
            new ConfirmationDialog().show(getChildFragmentManager(), FRAGMENT_DIALOG);
        } else {
            requestPermissions(new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
                                           @NonNull int[] grantResults) {
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults.length != 1 || grantResults[0] != PackageManager.PERMISSION_GRANTED) {
                ErrorDialog.newInstance(getString(R.string.request_permission))
                        .show(getChildFragmentManager(), FRAGMENT_DIALOG);
            }
        } else {
            super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)

FIND_PACKAGE( OpenMP REQUIRED)
if(OPENMP_FOUND)
    message("OPENMP FOUND")
    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${OpenMP_C_FLAGS}")
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${OpenMP_CXX_FLAGS}")
    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${OpenMP_EXE_LINKER_FLAGS}")
endif()

# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

include_directories(./ncnn-android-lib/include)

add_library( # Sets the name of the library.
        native-lib


        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        mobilenetssd.cpp)

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log)


# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
        native-lib

        ${CMAKE_SOURCE_DIR}/ncnn-android-lib/${ANDROID_ABI}/libncnn.a

        # Links the target library to the log library
        # included in the NDK.
        ${log-lib})

extern "C" JNIEXPORT jdoubleArray JNICALL
Java_com_chenty_testncnn_CameraNcnnFragment_detectyonly(JNIEnv *env, jobject thiz, jbyteArray frame, jint src_width,
                                jint src_height, jdoubleArray detect) {
    char *argb_frame = (char*)env->GetPrimitiveArrayCritical(frame, NULL);

    int size = env->GetArrayLength(frame);
    int objectcnt = 0;
    int i;

    //shift argb to rgba
    char *rgba = (char *)malloc(size);
    memcpy(rgba, argb_frame + 1, size - 1);

    env->ReleasePrimitiveArrayCritical(frame, argb_frame, JNI_ABORT);

    struct ai_object_t *obj = cpp_mobilenet_aidetect((const unsigned char *)rgba, src_width, src_height, &objectcnt);

    free(rgba);

    double *detect_out = (double *)env->GetPrimitiveArrayCritical(detect, NULL);
    if(objectcnt <= 0)
        objectcnt = 1;

    for(i = 0 ; i < objectcnt ; i++)
    {
        detect_out[i*6 + 0] = obj->label;
        detect_out[i*6 + 1] = obj->prob;
        detect_out[i*6 + 2] = obj->x;
        detect_out[i*6 + 3] = obj->y;
        detect_out[i*6 + 4] = obj->xe;
        detect_out[i*6 + 5] = obj->ye;
        obj++;
    }


    env->ReleasePrimitiveArrayCritical(detect, detect_out, JNI_ABORT);

    return detect;
}

现在已经可以在Log中看到SSD出来的目标了，很好，然后是数据绘制

            //split process function to prevent img reflash stop
            if(!mDetect_isbusy)
            {
                mDetect_isbusy = true;
                new Thread(new Runnable() {
                    public void run() {
                        mDetect_result = ncnnprocess_imgyuv(yuv, width, height);
                        mDetect_isbusy = false;
                    }
                }).start();
            }
            if(mDetect_result != null) {
                mSurfaceView.Draw(yuv, width, height, mDetect_result, 90);
            }