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Blitting Basics

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Two methods are available for copying images to a DirectDraw surface: IDirectDrawSurface5::Blt and IDirectDrawSurface5::BltFast. (A third method, IDirectDrawSurface5::BltBatch, is not implemented in this version of DirectX.) These methods are called on the destination surface and receive the source surface as a parameter. The destination and source surfaces can be one and the same, and you do not have to worry about overlap — DirectDraw takes care to preserve all source pixels before overwriting them.

Of the two implemented methods, Blt is the more flexible and BltFast is the faster — but only if there is no hardware blitter. You can determine the blitting capabilities of the hardware from the DDCAPS structure obtained in the lpDDDriverCaps parameter of the IDirectDraw4::GetCaps method. If the dwCaps member contains DDCAPS_BLT, the hardware has at least minimal blitting capabilities.

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