Archived:Scaling bitmaps using Symbian C++

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Article Metadata

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Tested with

Devices(s): Nokia N95

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Compatibility

Platform(s): S60 3rd Edition, MR

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Article

Keywords: CBitmapScaler

Created: tepaa (22 May 2008)

Last edited: lpvalente (03 Sep 2012)

Overview

This code snippet shows how to scale a bitmap using CBitmapScaler.

CBitmapScaler is the public API that clients can call for BitmapTransforms Library bitmap scaling.

Before scaling the bitmap you must decode CFbsBitmap from an image. Bitmaps are decoded using CImageDecoder.

MMP file

The following capabilities and libraries are required:

CAPABILITY None
LIBRARY bitmaptransforms.lib
LIBRARY fbscli.lib

Header

#include <bitmaptransforms.h>
#include <e32base.h>
#include <fbs.h>
 
class MBitmapScalerObserver
    {
    public:
        virtual void Completed(TInt aErr) = 0;
    };
 
class CMyBitmapScaler : public CActive
    {
    public:
        static CMyBitmapScaler* NewL(MBitmapScalerObserver* aObserver);
        virtual ~CMyBitmapScaler();
 
    public:
        void Scale( TInt aPercent );
        CFbsBitmap* GetBitmap();
 
    protected: // From CActive
        void DoCancel();
        void RunL();
        TInt RunError(TInt aError);
 
    private:
        CMyBitmapScaler(MBitmapScalerObserver* aObserver); 
        void ConstructL();          
 
    private:
        CFbsBitmap*             iBitmap;
        CBitmapScaler*          iScaler;
        MBitmapScalerObserver*   iObserver;
    };

Source

CMyBitmapScaler* CMyBitmapScaler::NewL( 
    MBitmapScalerObserver* aObserver )
    {
    CMyBitmapScaler* self = 
        new(ELeave) CMyBitmapScaler( aObserver );
    CleanupStack::PushL( self );
    self->ConstructL();
    CleanupStack::Pop(self);
    return self; 
    }
 
CMyBitmapScaler::CMyBitmapScaler( 
    MBitmapScalerObserver* aObserver ) : 
    CActive( EPriorityStandard ), iObserver( aObserver )
    {
    }
 
void CMyBitmapScaler::ConstructL()
    {
    iScaler = CBitmapScaler::NewL();
    CActiveScheduler::Add(this);
    }
 
CMyBitmapScaler::~CMyBitmapScaler()
    {
    Cancel();
    delete iBitmap;
    delete iScaler;
    }
 
void CMyBitmapScaler::DoCancel()
    {
    iScaler->Cancel();
    }
 
void CMyBitmapScaler::RunL()
    {
    iObserver->Completed(iStatus.Int());
    }
 
TInt CMyBitmapScaler::RunError(TInt aError)   
    {
    iObserver->Completed(aError);
    return KErrNone;
    }
 
void CMyBitmapScaler::Scale(TInt aPercent)
    {
    if (IsActive())
        {
        return;
        }
 
    TReal32 multiplier; 
    multiplier = aPercent/(TReal32)100.0;
 
    TInt newWidth = (TInt)(iBitmap->SizeInPixels().iWidth * multiplier);
    TInt newHeight = (TInt)(iBitmap->SizeInPixels().iHeight * multiplier);
 
    // The maintain aspect ratio is by default set to true
    iScaler->Scale( &iStatus, *iBitmap, TSize(newWidth,newHeight) );
 
    SetActive();
    }
 
CFbsBitmap* CMyBitmapScaler::GetBitmap()
    {
    return iBitmap;
    }

Using

TInt KScaleUpFactor = 150;    // Scale up by 50%
TInt KScaleDownFactor = 50;   // Scale down by 50%
 
iScaler = CMyBitmapScaler::NewL(this);
iScalser->Scale(KScaleUpFactor);

Postconditions

The bitmap is scaled.

See also

Archived:Displaying image information using Symbian C++