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如何捕捉图片

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Article Metadata

测试基于
设备:: Nokia N95 8GB

兼容于
平台: S60 3rd Edition, MR

平台安全性
能力: UserEnvironment

文章
关键词: CCamera, CCameraController
翻译:
hoolee
最后由 hamishwillee 在 06 Mar 2012 编辑
  • 详细描述

下列代码演示了如何使用Camera API(ecam.lib)捕捉一张图片。一般来说,操作流程如下:

  1. 生成一个camera controller作为UI和camera引擎的接口(这里放在CAppUi中)
  2. 调用CCameraController::InitializeCameraL(),它将会初始化相机引擎,并暂时掌控相机以便下面的操作。
  3. 掌控相机是一个异步的操作,完成后将会调用MCameraObserver::ReserveComplete()方法(或者就是CCameraEngine::ReserveComplete()方法的调用,因此CCameraEngine完成了MCameraObserver接口)
  4. 相机开始启动(CCamera::PowerOn()),同样这也是异步的操作,最终它将调用MCameraObserver::PowerOnComplete()方法。
  5. PowerOnComplete()方法准备开始捕捉,并设置引擎为空闲状态
  6. 当需要图片时,我们调用CCameraController::SnapL(),它将执行引擎的CCameraEngine::SnapL()命令,这才依次执行到实际的相机操作(CCamera::CaptureImage()方法)
  7. 捕捉图片也是一个异步的过程,完成后将调用MCameraObserver::ImageReady()

Contents

MMP文件

需要下列链接库和能力

CAPABILITY  UserEnvironment
LIBRARY ecam.lib

头文件: Camera.hrh

#ifndef __CAMERA_HRH_
#define __CAMERA_HRH_
 
enum TEngineState
{
EEngineNotReady,
ECameraReserved,
EEngineIdle,
ESnappingPicture
};
 
#endif /*__CAMERA_HRH_*/


头文件: CCameraController.h

#ifndef __CCAMERACONTROLLER_H_
#define __CCAMERACONTROLLER_H_
 
#include <e32base.h> // CBase
 
#include "Camera.hrh"
 
// Forward declarations
class CCameraEngine;
 
/**
* Interface between the UI and the camera engine.
*/

class CCameraController : public CBase
{
public: // Constructors and destructor
/**
* Two-phased constructor.
*/

static CCameraController* NewL();
 
/**
* Destructor.
*/

virtual ~CCameraController();
 
private: // Constructors and destructor
/**
* Symbian OS default constructor.
*/

CCameraController();
 
/**
* Symbian OS constructor.
*/

void ConstructL();
 
public: // New functions
/**
* Initializes the camera.
*/

void InitializeCameraL();
 
/**
* Snaps an image through the Camera API
*/

void SnapL();
 
private: // Data
CCameraEngine* iCameraEngine;
};
 
#endif /*__CCAMERACONTROLLER_H_*/


源文件 CCameraController.cpp

#include "Camera.hrh"
#include "CCameraController.h"
#include "CCameraEngine.h"
 
/*
-------------------------------------------------------------------------------
Two-phased constructor
-------------------------------------------------------------------------------
*/

CCameraController* CCameraController::NewL()
{
CCameraController* self = new (ELeave) CCameraController();
CleanupStack::PushL(self);
self->ConstructL();
CleanupStack::Pop(self);
return self;
}
 
/*
-------------------------------------------------------------------------------
Destructor. Frees allocated resources.
-------------------------------------------------------------------------------
*/

CCameraController::~CCameraController()
{
delete iCameraEngine;
}
 
/*
-------------------------------------------------------------------------------
C++ default constructor
-------------------------------------------------------------------------------
*/

CCameraController::CCameraController()
{
}
 
/*
-------------------------------------------------------------------------------
Symbian OS 2nd phase constructor
-------------------------------------------------------------------------------
*/

void CCameraController::ConstructL()
{
}
 
/*
-------------------------------------------------------------------------------
Initializes the still image capture engine
-------------------------------------------------------------------------------
*/

void CCameraController::InitializeCameraL()
{
if (!iCameraEngine)
{
iCameraEngine = CCameraEngine::NewL();
 
iCameraEngine->ReserveCameraL();
}
}
 
/*
-------------------------------------------------------------------------------
Takes an image
-------------------------------------------------------------------------------
*/

void CCameraController::SnapL()
{
iCameraEngine->SnapL();
}


头文件:CCameraEngine.h

#ifndef __CCAMERAENGINE_H_
#define __CCAMERAENGINE_H_
 
#include <ECam.h> // CCamera, MCameraObserver
 
#include "Camera.hrh"
 
class CCameraEngine : public MCameraObserver
{
public: // Constructors and destructor
/**
* Two-phased constructor.
*/

static CCameraEngine* NewL();
 
/**
* Destructor.
*/

virtual ~CCameraEngine();
 
private: // Constructors and destructor
/**
* Symbian OS default constructor.
*/

CCameraEngine();
 
/**
* Symbian OS constructor.
*/

void ConstructL();
 
private: // Methods from base classes
/**
* From MCameraObserver.
* Gets called when CCamera::Reserve() is completed.
*/

virtual void ReserveComplete(TInt aError);
 
/**
* From MCameraObserver.
* Gets called when CCamera::PowerOn() is completed.
*/

virtual void PowerOnComplete(TInt aError);
 
/**
* From MCameraObserver.
* Gets called when CCamera::StartViewFinderBitmapsL() is completed.
*/

virtual void ViewFinderFrameReady(CFbsBitmap& aFrame);
 
/**
* From MCameraObserver.
* Gets called when CCamera::CaptureImage() is completed.
*/

virtual void ImageReady(CFbsBitmap* aBitmap,
HBufC8* aData, TInt aError);
 
/**
* From MCameraObserver.
* Gets called when CCamera::StartVideoCapture() is completed.
*/

virtual void FrameBufferReady(MFrameBuffer* aFrameBuffer,
TInt aError);
 
public: // New Functions
/**
* Takes a picture.
*/

void SnapL();
 
/**
* Reserves the camera.
*/

void ReserveCameraL();
 
private: // Data
CCamera* iCamera;
TEngineState iState;
};
 
#endif /*__CCAMERAENGINE_H_*/


源文件 CCameraEngine.cpp

#include "Camera.hrh"
#include "CCameraEngine.h"
 
/*
-------------------------------------------------------------------------------
Two-phased constructor
-------------------------------------------------------------------------------
*/

CCameraEngine* CCameraEngine::NewL()
{
CCameraEngine* self = new (ELeave) CCameraEngine();
CleanupStack::PushL(self);
self->ConstructL();
CleanupStack::Pop(self);
return self;
}
 
/*
-------------------------------------------------------------------------------
Destructor. Frees allocated resources.
-------------------------------------------------------------------------------
*/

CCameraEngine::~CCameraEngine()
{
delete iCamera;
}
 
/*
-------------------------------------------------------------------------------
C++ default constructor
-------------------------------------------------------------------------------
*/

CCameraEngine::CCameraEngine()
{
iState = EEngineNotReady;
}
 
/*
-------------------------------------------------------------------------------
Symbian OS 2nd phase constructor
-------------------------------------------------------------------------------
*/

void CCameraEngine::ConstructL()
{
// TODO: It is assumed here that the device has a camera.
// Add error handling, if this may not be the case.
 
// Camera index 0 is the main camera
iCamera = CCamera::NewL(*this, 0);
}
 
/*
-------------------------------------------------------------------------------
Reserves the camera.
-------------------------------------------------------------------------------
*/

void CCameraEngine::ReserveCameraL()
{
iCamera->Reserve();
 
// On completion, MCameraObserver::ReserveComplete() will be called
}
 
/*
-------------------------------------------------------------------------------
Symbian Onboard Camera API observer. Gets called after CCamera::Reserve() is
called.
-------------------------------------------------------------------------------
*/

void CCameraEngine::ReserveComplete(TInt aError)
{
// TODO: Error handling
 
iState = ECameraReserved;
iCamera->PowerOn();
}
 
/*
-------------------------------------------------------------------------------
Symbian Onboard Camera API observer. Gets called after CCamera::PowerOn() is
called.
-------------------------------------------------------------------------------
*/

void CCameraEngine::PowerOnComplete(TInt aError)
{
// TODO: Error handling
 
// Prepare the capture. It is assumed here that the device supports
// capturing in EXIF JPEG format.
CCamera::TFormat format = CCamera::EFormatExif;
const TInt KImageSizeIndex = 1; // 2nd largest image size
iCamera->PrepareImageCaptureL(format, KImageSizeIndex);
 
// Everything is ready. Set the engine to idle state.
iState = EEngineIdle;
}
 
/*
-------------------------------------------------------------------------------
Symbian Onboard Camera API observer. Gets called after
CCamera::StartViewFinderBitmapsL() is called.
-------------------------------------------------------------------------------
*/

void CCameraEngine::ViewFinderFrameReady(CFbsBitmap& aFrame)
{
// Not important in this snippet
}
 
/*
-------------------------------------------------------------------------------
Symbian Onboard Camera API observer. Gets called after CCamera::CaptureImage()
is called.
-------------------------------------------------------------------------------
*/

void CCameraEngine::ImageReady(CFbsBitmap* aBitmap, HBufC8* aData, TInt aError)
{
// TODO: Error handling
 
// Image saving is not demonstrated in this snippet
// ...
 
// The engine is ready for another go
iState = EEngineIdle;
}
 
/*
-------------------------------------------------------------------------------
Symbian Onboard Camera API observer. Gets called once
CCamera::StartVideoCapture() is called.
-------------------------------------------------------------------------------
*/

void CCameraEngine::FrameBufferReady(MFrameBuffer* aFrameBuffer, TInt aError)
{
// TODO: Error handling
 
// Capturing video is not demonstrated in this snippet
}
 
/*
-------------------------------------------------------------------------------
Takes a picture
-------------------------------------------------------------------------------
*/

void CCameraEngine::SnapL()
{
// Snapping a picture is only possible if the engine is in idle state
if (iState == EEngineIdle)
{
iState = ESnappingPicture;
iCamera->CaptureImage();
 
// On completion, MCameraObserver::ImageReady() will be called
}
else
{
User::Leave(KErrNotReady);
}
}


源文件:CAppUi.cpp

#include "CCameraController.h"
 
iCameraController = CCameraController::NewL();
iCameraController->InitializeCameraL();
This page was last modified on 6 March 2012, at 03:48.
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