【入门到实战】OpenHarmony南向子系统开发：相机拍照开发指南

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相机拍照开发

使用场景

使用Camera产生图片帧（拍照）。

接口说明

表1 API列表

类名	接口名	描述
CameraKit	int32_t GetCameraIds(std::list<string> cameraList)	获取cameraId列表
CameraKit	CameraAbility& GetCameraAbility(string cameraId)	获取指定camera的能力
CameraKit	void RegisterCameraDeviceCallback(CameraDeviceCallback* callback, EventHandler* handler)	注册camera设备状态回调
CameraKit	void UnregisterCameraDeviceCallback(CameraDeviceCallback* callback)	去注册camera设备状态回调
CameraKit	void CreateCamera(string cameraId, CameraStateCallback* callback, EventHandler* handler)	创建camera实例
Camera	string GetCameraId()	获取cameraID
Camera	CameraConfig& GetCameraConfig()	获取camera配置信息
Camera	FrameConfig& GetFrameConfig(int32_t type)	获取捕获帧类型
Camera	void Configure(CameraConfig& config)	配置camera
Camera	void Release()	释放camera
Camera	int TriggerLoopingCapture(FrameConfig& frameConfig)	开始循环帧捕获
Camera	void StopLoopingCapture()	停止循环帧捕获
Camera	int32_t TriggerSingleCapture(FrameConfig& frameConfig)	截图
CameraConfig	void SetFrameStateCallback(FrameStateCallback* callback, EventHandler* handler);	设置帧状态回调
CameraConfig	static CameraConfig* CreateCameraConfig()	创建camera配置信息实例
CameraAbility	std::list<Size> GetSupportedSizes(int format)	根据类型获取支持输出图像尺寸大小
CameraAbility	std::list<T> GetParameterRange(uint32_t key)	获取支持的参数范围
CameraDevice	CameraDeviceCallback()	camera设备回调类构造函数
CameraDevice	void OnCameraStatus(std::string cameraId, int32_t status)	camera设备状态变化时的回调
CameraStateCallback	CameraStateCallback()	camera状态回调类构造函数
CameraStateCallback	void OnConfigured(Camera& camera)	camera配置成功回调
CameraStateCallback	void OnConfigureFailed(Camera& camera,int32_t errorCode)	camera配置失败回调
CameraStateCallback	void OnCreated(Camera& camera)	camera创建成功回调
CameraStateCallback	void OnCreateFailed(std::string cameraId,int32_t errorCode)	camera创建失败回调
CameraStateCallback	void OnReleased(Camera& camera)	camera释放回调
FrameStateCallback	FrameStateCallback()	帧状态回调类构造函数
FrameStateCallback	void OnFrameFinished(Camera& camera, FrameConfig& frameConfig, FrameResult& frameResult)	拍照帧完成回调
FrameStateCallback	void OnFrameError(Camera& camera, FrameConfig& frameConfig, int32_t errorCode, FrameResult& frameResult)	拍照帧异常回调
FrameConfig	int32_t GetFrameConfigType()	获取帧配置类型
FrameConfig	std::list<OHOS::Surface> GetSurfaces()	获取帧配置的surface
FrameConfig	void AddSurface(OHOS::AGP::UISurface& surface);	添加surface
FrameConfig	void RemoveSurface(OHOS::AGP::UISurface& surface);	删除surface

约束与限制

无。

开发步骤

实现设备状态回调的派生类，用户在设备状态发生变更（如新插入相机设备/相机掉线）时，自定义操作。

class SampleCameraDeviceCallback : public CameraDeviceCallback {
    void OnCameraStatus(std::string cameraId, int32_t status) override
    {
        //do something when camera is available/unavailable
    }
};

实现帧事件回调的派生类，这里在拿到帧数据以后将其转存为文件。

static void SampleSaveCapture(const char *p, uint32_t size)
{
    cout << "Start saving picture" << endl;
    struct timeval tv;
    gettimeofday(&tv, NULL);
    struct tm *ltm = localtime(&tv.tv_sec);
    if (ltm != nullptr) {
        ostringstream ss("Capture_");
        ss << "Capture" << ltm->tm_hour << "-" << ltm->tm_min << "-" << ltm->tm_sec << ".jpg";

        ofstream pic("/sdcard/" + ss.str(), ofstream::out | ofstream::trunc);
        cout << "write " << size << " bytes" << endl;
        pic.write(p, size);
        cout << "Saving picture end" << endl;
    }
}

class TestFrameStateCallback : public FrameStateCallback {
    void OnFrameFinished(Camera &camera, FrameConfig &fc, FrameResult &result) override
    {
        cout << "Receive frame complete inform." << endl;
        if (fc.GetFrameConfigType() == FRAME_CONFIG_CAPTURE) {
            cout << "Capture frame received." << endl;
            list<Surface *> surfaceList = fc.GetSurfaces();
            for (Surface *surface : surfaceList) {
                SurfaceBuffer *buffer = surface->AcquireBuffer();
                if (buffer != nullptr) {
                    char *virtAddr = static_cast<char *>(buffer->GetVirAddr());
                    if (virtAddr != nullptr) {
                        SampleSaveCapture(virtAddr, buffer->GetSize());
                    }
                    surface->ReleaseBuffer(buffer);
                }
                delete surface;
            }
            delete &fc;
        }
    }
};

实现相机状态回调的派生类，自定义相机状态发生变化（配置成功/失败，创建成功/失败)时的操作。

class SampleCameraStateMng : public CameraStateCallback {
public:
    SampleCameraStateMng() = delete;
    SampleCameraStateMng(EventHandler &eventHdlr) : eventHdlr_(eventHdlr) {}
    ~SampleCameraStateMng()
    {
        if (recordFd_ != -1) {
            close(recordFd_);
        }
    }
    void OnCreated(Camera &c) override
    {
        cout << "Sample recv OnCreate camera." << endl;
        auto config = CameraConfig::CreateCameraConfig();
        config->SetFrameStateCallback(&fsCb_, &eventHdlr_);
        c.Configure(*config);
        cam_ = &c;
    }
    void OnCreateFailed(const std::string cameraId, int32_t errorCode) override {}
    void OnReleased(Camera &c) override {}
};

创建CameraKit，用于创建和获取camera信息。

CameraKit *camKit = CameraKit::GetInstance();
list<string> camList = camKit->GetCameraIds();
string camId;
for (auto &cam : camList) {
    cout << "camera name:" << cam << endl;
    const CameraAbility *ability = camKit->GetCameraAbility(cam);
    /* find camera which fits user's ability */
    list<CameraPicSize> sizeList = ability->GetSupportedSizes(0);
    if (find(sizeList.begin(), sizeList.end(), CAM_PIC_1080P) != sizeList.end()) {
        camId = cam;
        break;
    }
}

创建Camera实例。

EventHandler eventHdlr; // Create a thread to handle callback events
SampleCameraStateMng CamStateMng(eventHdlr);

camKit->CreateCamera(camId, CamStateMng, eventHdlr);

根据步骤1、步骤2、步骤3中的回调设计，同步等待 OnCreated 回调拿到 cam_ 之后，进行相关操作。

void OnCreated(Camera &c) override
{
    cout << "Sample recv OnCreate camera." << endl;
    auto config = CameraConfig::CreateCameraConfig();
    config->SetFrameStateCallback(&fsCb_, &eventHdlr_);
    c.Configure(*config);
    cam_ = &c;
}

void Capture()
{
    if (cam_ == nullptr) {
        cout << "Camera is not ready." << endl;
        return;
    }
    FrameConfig *fc = new FrameConfig(FRAME_CONFIG_CAPTURE);
    Surface *surface = Surface::CreateSurface();
    if (surface == nullptr) {
        delete fc;
        return;
    }
    surface->SetWidthAndHeight(1920, 1080); /* 1920:width,1080:height */
    fc->AddSurface(*surface);
    cam_->TriggerSingleCapture(*fc);
}