Bitmap class for direct screen access
This article shows a bitmap class that can be used to store images for quick rendering to the screen buffer when using direct screen access. This might be used, for example, in rendering sprites in a DSA enabled game
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Contents |
Remarks for the sample
- It assumes, that images are stored in an mbm file in the application's private directory
- It reserves space on the heap to store the image and converts the bitmap in a way it can be directly rendered in the screen buffer
- Remember to use /c24 switch when creating mbm file with mifconv tool to ensure right color depth
Links
Code
Header file (.h)
#define TPixel TUint32
class CMyBitmap : public CBase
{
...
TPixel* iData;
TSize iSize;
...
};
Source file (cpp)
...
_LIT( KMyBitmapFile,"MyGame.mbm" );
// CMyBitmap class represents a bitmap ready for rendering
// with direct screen access
// aIndex is the image's index in the mbm file
void CMyBitmap::ConstructL( TInt aIndex )
{
CFbsBitmap* image = new( ELeave ) CFbsBitmap;
CleanupStack::PushL( image );
// Finding out the location of the mbm file
TFileName path;
#ifdef __WINS__
path.Append( _L("z:\\resource\\apps\\") );
#else
path.Copy(CEikonEnv::Static()->EikAppUi()->Application()->AppFullName().Left(2));
TFileName relPath;
CEikonEnv::Static()->FsSession().PrivatePath( relPath );
path.Append( relPath);
#endif
path.Append( KMyBitmapFile );
// Load bitmap
User::LeaveIfError( image->Load( path, aIndex, EFalse ) );
// Creating space on heap
iSize = image->SizeInPixels();
// Remember to delete it in the destructor
iData = new ( ELeave ) TPixel[ iSize.iWidth * iSize.iHeight ];
// TBitmapUtil helps accessing pixels safely
TBitmapUtil sourceUtil( image );
for ( TInt y = 0; y < iSize.iHeight; y++ )
{
sourceUtil.Begin( TPoint( 0, y ) );
for ( TInt x = 0; x < iSize.iWidth; x++ )
{
*(iData + y * iSize.iWidth + x) = sourceUtil.GetPixel();
sourceUtil.IncXPos();
}
sourceUtil.End();
}
CleanupStack::PopAndDestroy();
}
...
18 Sep
2009
Game programming requires faster rendering to the screen help achieving this on can draw images directly to the screen. However, storing the most frequently used sprites in the memory and then drawing it from there can increase the speed even better. Well commented code snippet has been provided showing the usage of TBitmapUtil class to access image data of a bitmap - providing access to individual pixels.