CDC::BitBlt

Статья
10/16/2008

Copies a bitmap from the source device context to this current device context.

BOOL BitBlt(
   int x,
   int y,
   int nWidth,
   int nHeight,
   CDC* pSrcDC,
   int xSrc,
   int ySrc,
   DWORD dwRop 
);

Параметры

x
Specifies the logical x-coordinate of the upper-left corner of the destination rectangle.
y
Specifies the logical y-coordinate of the upper-left corner of the destination rectangle.
nWidth
Specifies the width (in logical units) of the destination rectangle and source bitmap.
nHeight
Specifies the height (in logical units) of the destination rectangle and source bitmap.
pSrcDC
Pointer to a CDC object that identifies the device context from which the bitmap will be copied. It must be NULL if dwRop specifies a raster operation that does not include a source.
xSrc
Specifies the logical x-coordinate of the upper-left corner of the source bitmap.
ySrc
Specifies the logical y-coordinate of the upper-left corner of the source bitmap.
dwRop
Specifies the raster operation to be performed. Raster-operation codes define how the GDI combines colors in output operations that involve a current brush, a possible source bitmap, and a destination bitmap. See BitBlt in the Windows SDK for a list of the raster-operation codes for dwRop and their descriptions

For a complete list of raster-operation codes, see About Raster Operation Codes in the Windows SDK.

Возвращаемое значение

Nonzero if the function is successful; otherwise 0.

Заметки

The application can align the windows or client areas on byte boundaries to ensure that the BitBlt operations occur on byte-aligned rectangles. (Set the CS_BYTEALIGNWINDOW or CS_BYTEALIGNCLIENT flags when you register the window classes.)

BitBlt operations on byte-aligned rectangles are considerably faster than BitBlt operations on rectangles that are not byte aligned. If you want to specify class styles such as byte-alignment for your own device context, you will have to register a window class rather than relying on the Microsoft Foundation classes to do it for you. Use the global function AfxRegisterWndClass.

GDI transforms nWidth and nHeight, once by using the destination device context, and once by using the source device context. If the resulting extents do not match, GDI uses the Windows StretchBlt function to compress or stretch the source bitmap as necessary.

If destination, source, and pattern bitmaps do not have the same color format, the BitBlt function converts the source and pattern bitmaps to match the destination. The foreground and background colors of the destination bitmap are used in the conversion.

When the BitBlt function converts a monochrome bitmap to color, it sets white bits (1) to the background color and black bits (0) to the foreground color. The foreground and background colors of the destination device context are used. To convert color to monochrome, BitBlt sets pixels that match the background color to white and sets all other pixels to black. BitBlt uses the foreground and background colors of the color device context to convert from color to monochrome.

Note that not all device contexts support BitBlt. To check whether a given device context does support BitBlt, use the GetDeviceCaps member function and specify the RASTERCAPS index.