MaskBlt function (wingdi.h)

Article
10/13/2021

The MaskBlt function combines the color data for the source and destination bitmaps using the specified mask and raster operation.

Syntax

BOOL MaskBlt(
  [in] HDC     hdcDest,
  [in] int     xDest,
  [in] int     yDest,
  [in] int     width,
  [in] int     height,
  [in] HDC     hdcSrc,
  [in] int     xSrc,
  [in] int     ySrc,
  [in] HBITMAP hbmMask,
  [in] int     xMask,
  [in] int     yMask,
  [in] DWORD   rop
);

Parameters

[in] hdcDest

A handle to the destination device context.

[in] xDest

The x-coordinate, in logical units, of the upper-left corner of the destination rectangle.

[in] yDest

The y-coordinate, in logical units, of the upper-left corner of the destination rectangle.

[in] width

The width, in logical units, of the destination rectangle and source bitmap.

[in] height

The height, in logical units, of the destination rectangle and source bitmap.

[in] hdcSrc

A handle to 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.

[in] xSrc

The x-coordinate, in logical units, of the upper-left corner of the source bitmap.

[in] ySrc

The y-coordinate, in logical units, of the upper-left corner of the source bitmap.

[in] hbmMask

A handle to the monochrome mask bitmap combined with the color bitmap in the source device context.

[in] xMask

The horizontal pixel offset for the mask bitmap specified by the hbmMask parameter.

[in] yMask

The vertical pixel offset for the mask bitmap specified by the hbmMask parameter.

[in] rop

The foreground and background ternary raster operation codes (ROPs) that the function uses to control the combination of source and destination data. The background raster operation code is stored in the high-order byte of the high-order word of this value; the foreground raster operation code is stored in the low-order byte of the high-order word of this value; the low-order word of this value is ignored, and should be zero. The macro MAKEROP4 creates such combinations of foreground and background raster operation codes.

For a discussion of foreground and background in the context of this function, see the following Remarks section.

For a list of common raster operation codes (ROPs), see the BitBlt function. Note that the CAPTUREBLT ROP generally cannot be used for printing device contexts.

Return value

If the function succeeds, the return value is nonzero.

If the function fails, the return value is zero.

Remarks

The MaskBlt function uses device-dependent bitmaps.

A value of 1 in the mask specified by hbmMask 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 transformation 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 FALSE) if the source device context identifies an enhanced-metafile device context.

Not all devices support the MaskBlt function. An application should call the GetDeviceCaps function with the nIndex parameter as RC_BITBLT 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.

ICM: No color management is performed when blits occur.

When used in a multiple monitor system, both hdcSrc and hdcDest must refer to the same device or the function will fail. To transfer data between DCs for different devices, convert the memory bitmap (compatible bitmap, or DDB) to a DIB by calling GetDIBits. To display the DIB to the second device, call SetDIBits or StretchDIBits.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wingdi.h (include Windows.h)
Library	Gdi32.lib
DLL	Gdi32.dll