From Forum Nokia Wiki

The CImage_Reader implementation illustrates how to use CImageDecoder to open and read different types of images and how to convert them to the Symbian bitmap format, which then can be used to draw the image to the screen.

The GetFileType function is used to determine the type of the image file, and if the image type is not recognized by the system it will be indicated by the iError variable. The MImageReadyCallBack callback interface is used to notify of the completion of the image loading.

Image_Reader.cpp

#include <cntfield.h>
#include <cntdef.h> 
#include <cntitem.h>
#include <cntfldst.h>
#include <cntdb.h>
#include <COEMAIN.H>
#include <APMREC.H>
#include <APGCLI.H>
 
 
CImage_Reader::CImage_Reader(MImageReadyCallBack& aNotify)
:CActive(0),iNotify(aNotify)
    {
    }
 
CImage_Reader::~CImage_Reader()
{
	Cancel();
	delete iFrame;
        delete iImageDecoder;
}
 
 
void CImage_Reader::ConstructL(const TDesC& aFileName)
{
	CActiveScheduler::Add(this);
 
	iImageName.Copy(aFileName);
 
	TBuf8<255> ImageType;
	GetFileType(aFileName, ImageType);
 
	if(ImageType.Length() && iImageName.Length())
	{		
		iImageDecoder = CImageDecoder::FileNewL(CCoeEnv::Static()->FsSession(),aFileName,ImageType);
 
		delete iFrame;
		iFrame = NULL;
		iFrame = new(ELeave)CFbsBitmap();
		iFrame->Create(iImageDecoder->FrameInfo(0).iOverallSizeInPixels,iImageDecoder->FrameInfo(0).iFrameDisplayMode);
 
		iImageDecoder->Convert(&iStatus,*iFrame,0);
		SetActive();
	}
	else
	{
		TRequestStatus* status=&iStatus;
		User::RequestComplete(status, KErrNotSupported);
		SetActive();
	}
}
 
void CImage_Reader::GetFileType(const TDesC& aFileName, TDes8& aFileType)
{
	TEntry FileEntry;
 
	if(CCoeEnv::Static()->FsSession().Entry(aFileName,FileEntry) == KErrNone)
	{
		TBuf8<255> FileBuffer;
 
		if(!FileEntry.IsDir())
		{
			TInt FileSize = FileEntry.iSize;
 
			if(FileSize > 255)
			{
				FileSize = 255;
			}
 
			if(CCoeEnv::Static()->FsSession().ReadFileSection(aFileName,0,FileBuffer,FileSize) == KErrNone)
			{
				RApaLsSession RSession;
				if(RSession.Connect() == KErrNone)
				{	
					TDataRecognitionResult FileDataType;
 
					RSession.RecognizeData(aFileName,FileBuffer,*&FileDataType);
 
					if(FileDataType.iConfidence > aResult.iConfidence)
					{
						aFileType.Copy(FileDataType.iDataType.Des8());
					}
 
					RSession.Close();
				}
			}
		}
	}
}
 
void CImage_Reader::DoCancel()
{
	iImageDecoder->Cancel();
}
 
CFbsBitmap* CImage_Reader::Bitmap()
{
	return iFrame;
}
 
 
void CImage_Reader::RunL()
{
	iNotify.ImageReadyL(iStatus.Int());
}

Image_Reader.h

#include <e32base.h>
#include <coecntrl.h>
#include <w32std.h>
#include <e32std.h>
#include <cntdef.h>
#include <cntdb.h> 
#include <ImageConversion.h>
 
class CFbsBitmap;
 
	class MImageReadyCallBack
	{
	public:
		virtual void ImageReadyL(const TInt& aError) = 0;
		};
 
	class CImage_Reader : public CActive
	{
	public:
	    CImage_Reader(MImageReadyCallBack& aNotify);
	    void ConstructL(const TDesC& aFileName);
	    ~CImage_Reader();
	public:
	    CFbsBitmap* Bitmap();
	protected:
		void DoCancel();
		void RunL();
	private:
		void GetFileType(const TDesC& aFileName, TDes8& aFileType);
	private:
		MImageReadyCallBack&	iNotify;
		CImageDecoder*			iImageDecoder;
		CFbsBitmap*				iFrame;
		TFileName				iImageName;
	};

Related links:

• Resize png/jpg image in Symbian