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CDC::SetStretchBltMode

Sets the bitmap-stretching mode for the StretchBlt member function.

int SetStretchBltMode(
   int nStretchMode 
);

Parameters

  • nStretchMode
    Specifies the stretching mode. It can be any of the following values:

    Value

    Description

    BLACKONWHITE

    Performs a Boolean AND operation using the color values for the eliminated and existing pixels. If the bitmap is a monochrome bitmap, this mode preserves black pixels at the expense of white pixels.

    COLORONCOLOR

    Deletes the pixels. This mode deletes all eliminated lines of pixels without trying to preserve their information.

    HALFTONE

    Maps pixels from the source rectangle into blocks of pixels in the destination rectangle. The average color over the destination block of pixels approximates the color of the source pixels.

     

    After setting the HALFTONE stretching mode, an application must call the Win32 function SetBrushOrgEx to set the brush origin. If it fails to do so, brush misalignment occurs.

    STRETCH_ANDSCANS

    Windows 95/98: Same as BLACKONWHITE

    STRETCH_DELETESCANS

    Windows 95/98: Same as COLORONCOLOR

    STRETCH_HALFTONE

    Windows 95/98: Same as HALFTONE.

    STRETCH_ORSCANS

    Windows 95/98: Same as WHITEONBLACK

    WHITEONBLACK

    Performs a Boolean OR operation using the color values for the eliminated and existing pixels. If the bitmap is a monochrome bitmap, this mode preserves white pixels at the expense of black pixels.

Return Value

The previous stretching mode. It can be STRETCH_ANDSCANS, STRETCH_DELETESCANS, or STRETCH_ORSCANS.

Remarks

The bitmap-stretching mode defines how information is removed from bitmaps that are compressed by using the function.

The BLACKONWHITE (STRETCH_ANDSCANS) and WHITEONBLACK (STRETCH_ORSCANS) modes are typically used to preserve foreground pixels in monochrome bitmaps. The COLORONCOLOR (STRETCH_DELETESCANS) mode is typically used to preserve color in color bitmaps.

The HALFTONE mode requires more processing of the source image than the other three modes; it is slower than the others, but produces higher quality images. Also note that SetBrushOrgEx must be called after setting the HALFTONE mode to avoid brush misalignment.

Additional stretching modes might also be available depending on the capabilities of the device driver.

Requirements

Header: afxwin.h

See Also

Concepts

CDC Class

CDC Members

Hierarchy Chart

CDC::GetStretchBltMode

CDC::StretchBlt

SetStretchBltMode