通过CImageDecoder解码显示GIF动画

CGif_Reader是一个简单的GIF动画解析类，可以用来显示一个GIF动画在CCoeControl上。要构造CGif_Reader的话，需要增加下列代码在您container的ConstructL()函数中。

iGif_Reader = new(ELeave)CGif_Reader(*this);

iGif_Reader->ConstructL(KTxtFileName);

KTxtFileName是一个GIF文件名称（有完整的路径包括盘符，路径，扩展名）。要绘制GIF动画你需要在container的Draw()中完成如下代码

void CMycontainer::Draw(const TRect& aRect) const

{

    CWindowGc& gc = SystemGc();       

    if(iGifReader)
 {
  if(iGifReader->Bitmap())
  {
   if(iGifReader->Bitmap()->Handle())
   {
   gc.DrawBitmap(aRect, iGifReader->Bitmap());                
   }
  }       
 }

}

 

Gif_Reader.cpp

#include "Gif_Reader.h"

 

#include <cntfield.h>

#include <cntdef.h>

#include <cntitem.h>

#include <cntfldst.h>

#include <cntdb.h>

#include <COEMAIN.H>

#include <akniconutils.h>

 

_LIT8(KtxTypeImageGif_8                     ,"image/gif");

 

const TInt KFrameTimeOut = 200000;// 0.2 sec frame timeout

 

 

CGif_Reader::CGif_Reader(CCoeControl& aParent)

:

CActive(0), iParent(aParent), iCurrImg(-1)

    {

    }

 

CGif_Reader::~CGif_Reader()

{

         Cancel();

         delete iExampleTimer;

         delete iImageDecoder;

         delete iFrame;

         delete iFrameImg;

         delete iFrameMsk;

 

         delete iBitmapDevice;

         delete iGraphicsContext;

}

 

 

void CGif_Reader::ConstructL(const TDesC& aFileName)

{

         CActiveScheduler::Add(this);

         iImageDecoder = CImageDecoder::FileNewL(CCoeEnv::Static()->FsSession(),

aFileName, KtxTypeImageGif_8);

         iCurrCount = iImageDecoder->FrameCount();

 

         if(iCurrCount > 0)

         {

                 iFrame = new(ELeave)CFbsBitmap();

                 iFrame->Create(iImageDecoder->FrameInfo(0).iOverallSizeInPixels,

iImageDecoder->FrameInfo(0).iFrameDisplayMode);

 

                 iBitmapDevice = CFbsBitmapDevice::NewL(iFrame);

                 User::LeaveIfError(iBitmapDevice->CreateContext(iGraphicsContext));

         }

}

 

void CGif_Reader::TimerExpired(TAny* /*aTimer*/, TInt /*aError*/)

{

         Cancel();

         NextImageL();

}

 

 

void CGif_Reader::NextImageL(void)

{

         iCurrImg++;

         if(iCurrImg >= iCurrCount || iCurrImg < 0)

         {

                 iCurrImg = 0;

         }

 

         delete iFrameImg;

         iFrameImg = NULL;

         iFrameImg = new(ELeave)CFbsBitmap();

         iFrameImg->Create(iImageDecoder->FrameInfo(iCurrImg).iOverallSizeInPixels,

iImageDecoder->FrameInfo(iCurrImg).iFrameDisplayMode);

 

         delete iFrameMsk;

         iFrameMsk = NULL;

         iFrameMsk = new(ELeave)CFbsBitmap();

         iFrameMsk->Create(iImageDecoder->FrameInfo(iCurrImg).iOverallSizeInPixels,

EGray2);

 

         iImageDecoder->Convert(&iStatus, *iFrameImg, *iFrameMsk, iCurrImg);

         SetActive();    

}

 

 

void CGif_Reader::DoCancel()

{

         iImageDecoder->Cancel();

}

 

CFbsBitmap* CGif_Reader::Bitmap()

{

         return iFrame;

}

 

 

void CGif_Reader::RunL()

{

         if(iFrameMsk && iFrameImg && iFrame && iGraphicsContext)

         {

                 if(iFrameMsk->Handle() && iFrameImg->Handle() && iFrame->Handle())

                 {

                          if(TFrameInfo::ERestoreToBackground & iImageDecoder->FrameInfo(iCurrImg).iFlags)

                          {

                                   iGraphicsContext->DrawBitmap(

TRect(0, 0, iFrame->SizeInPixels().iWidth, iFrame->SizeInPixels().iHeight),

iFrameImg);

                          }

                          else

                          {

                                   iGraphicsContext->DrawBitmapMasked(iImageDecoder->FrameInfo

 

(iCurrImg).iFrameCoordsInPixels,

iFrameImg, TRect(0, 0, iFrameImg->SizeInPixels().iWidth, iFrameImg->SizeInPixels().iHeight),

iFrameMsk, EFalse);

                          }

                 }

         }

 

         iParent.DrawNow();       

 

         if(iStatus.Int() != KErrCancel)

         {

                 if(!iExampleTimer)

                 {

                          iExampleTimer = CExampleTimer::NewL(CActive::EPriorityStandard, *this);

                 }       

 

                 iExampleTimer->After(KFrameTimeOut);

         }

}

 

Gif_Reader.h

#include <e32base.h>

#include <coecntrl.h>

#include <w32std.h>

#include <e32std.h>

#include <cntdef.h>

#include <cntdb.h>

#include <ImageConversion.h>

 

#include "CExampleTimer.h"

 

 

 

         class CGif_Reader : public CActive,MExampleTimerNotify

         {

         public:

             CGif_Reader(CCoeControl& aParent);

             void ConstructL(const TDesC& aFileName);

             ~CGif_Reader();

             CFbsBitmap* Bitmap();

         protected:

                 void TimerExpired(TAny* aTimer,TInt aError);

                 void DoCancel();

                 void RunL();

         private:

                 void NextImageL(void);

                 void FinnishReadL(void);

         private:

                 CCoeControl&              iParent;

                 TInt                               iCurrImg,iCurrCount;

                 CImageDecoder*            iImageDecoder;

                 CFbsBitmap*                        iFrame;

                 CFbsBitmap*                        iFrameMsk;

                 CFbsBitmap*                        iFrameImg;

                 CExampleTimer*            iExampleTimer;

                 CFbsBitGc*                         iGraphicsContext;

                 CFbsBitmapDevice*         iBitmapDevice;

         };