If you need direct access the bitmap data instead going through
drawing to it using wxMemoryDC you need to use the wxPixelData
class (either wxNativePixelData for RGB bitmaps or wxAlphaPixelData
- for bitmaps with an additionaly alpha channel).
+ for bitmaps with an additionally alpha channel).
Note that many wxBitmap functions take a @e type parameter, which is a
value of the ::wxBitmapType enumeration.