CDC::MaskBlt

BOOL MaskBlt( int x, int y, int nWidth, int nHeight, CDC* pSrcDC, int xSrc, int ySrc, CBitmap& maskBitmap, int xMask, int yMask, DWORD dwRop );

Return Value

Nonzero if the function is successful; otherwise 0.

Parameters

Specifies the logical x-coordinate of the upper-left corner of the destination rectangle.

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

Identifies the device context from which the bitmap is to be copied. It must be zero if the dwRop parameter 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.

maskBitmap

Identifies the monochrome mask bitmap combined with the color bitmap in the source device context.

xMask

Specifies the horizontal pixel offset for the mask bitmap specified by the maskBitmap parameter.

yMask

Specifies the vertical pixel offset for the mask bitmap specified by the maskBitmap parameter.

dwRop

Specifies both foreground and background ternary raster operation codes, which the function uses to control the combination of source and destination data. The background raster operation code is stored in the high byte of the high word of this value; the foreground raster operation code is stored in the low byte of the high word of this value; the low word of this value is ignored, and should be zero. The macro MAKEROP4 creates such combinations of foreground and background raster operation codes. See the Remarks section for a discussion of foreground and background in the context of this function. See the BitBlt member function for a list of common raster operation codes.

Remarks

Combines the color data for the source and destination bitmaps using the given mask and raster operation. A value of 1 in the mask specified by maskBitmap indicates that the foreground raster operation code specified by dwRop should be applied at that location. A value of 0 in the mask indicates that the background raster operation code specified by dwRop should be applied at that location. If the raster operations require a source, the mask rectangle must cover the source rectangle. If it does not, the function will fail. If the raster operations do not require a source, the mask rectangle must cover the destination rectangle. If it does not, the function will fail.

If a rotation or shear transformation is in effect for the source device context when this function is called, an error occurs. However, other types of transformations are allowed.

If the color formats of the source, pattern, and destination bitmaps differ, this function converts the pattern or source format, or both, to match the destination format. If the mask bitmap is not a monochrome bitmap, an error occurs. When an enhanced metafile is being recorded, an error occurs (and the function returns 0) if the source device context identifies an enhanced-metafile device context. Not all devices support MaskBlt. An application should call GetDeviceCaps to determine whether a device supports this function. If no mask bitmap is supplied, this function behaves exactly like BitBlt, using the foreground raster operation code. The pixel offsets in the mask bitmap map to the point (0,0) in the source device context’s bitmap. This is useful for cases in which a mask bitmap contains a set of masks; an application can easily apply any one of them to a mask-blitting task by adjusting the pixel offsets and rectangle sizes sent to MaskBlt.

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