bitblt

BitBlt, short for bit-block transfer, is a function in the Windows Graphics Device Interface (GDI) used to copy a rectangular block of pixels from a source device context (DC) to a destination DC. The operation can copy pixels directly or combine them with the destination using a raster-operation code (ROP). BitBlt is a fundamental Blitting primitive in Win32 programming and is commonly used for tasks such as image rendering, scrolling, double buffering, and basic image compositing.

Prototype and behavior: BOOL BitBlt(HDC hdcDest, int nXDest, int nYDest, int nWidth, int nHeight, HDC hdcSrc, int nXSrc, int nYSrc, DWORD dwRop); The function returns a nonzero value on success and zero on failure (use GetLastError for details). hdcDest is the destination DC; nXDest/nYDest specify the upper-left corner in the destination; nWidth/nHeight define the size of the rectangle to transfer. hdcSrc is the source DC; nXSrc/nYSrc specify the upper-left corner in the source. dwRop selects how the source and destination pixels are combined during the transfer.

Rasters and codes: The dwRop parameter encodes the raster operation to apply. Common examples include SRCCOPY (copy source to destination), SRCINVERT, SRCAND, SRCPAINT, and DSTINVERT. There are numerous other codes, enabling various ways to blend or mask pixels.

Notes: BitBlt supports both monochrome and color bitmaps and can handle overlapping source and destination if drawn within the same DC. For scaling, stretching, or more complex masking, other functions such as StretchBlt, MaskBlt, and TransparentBlt are available.