SetStretchBltMode

The SetStretchBltMode function sets the bitmap stretching mode in the specified device context.

int SetStretchBltMode(
  HDC hdc,           // handle to device context
  int iStretchMode   // bitmap stretching mode
);
 

Parameters

hdc
Handle to the device context.
iStretchMode
Specifies the stretching mode. It can be one 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 SetBrushOrgEx function to set the brush origin. If it fails to do so, brush misalignment occurs.
STRETCH_ANDSCANS Same as BLACKONWHITE.
STRETCH_DELETESCANS Same as COLORONCOLOR.
STRETCH_HALFTONE Same as HALFTONE.
STRETCH_ORSCANS 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 Values

If the function succeeds, the return value is the previous stretching mode.

If the function fails, the return value is zero.

Windows NT: To get extended error information, call GetLastError.

Remarks

The stretching mode defines how the system combines rows or columns of a bitmap with existing pixels on a display device when an application calls the StretchBlt 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.

QuickInfo

  Windows NT: Requires version 3.1 or later.
  Windows: Requires Windows 95 or later.
  Windows CE: Unsupported.
  Header: Declared in wingdi.h.
  Import Library: Use gdi32.lib.

See Also

Bitmaps Overview, Bitmap Functions, GetStretchBltMode, SetBrushOrgEx, StretchBlt