SetStretchBltMode function

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

Syntax

int SetStretchBltMode(
  HDC hdc,
  int mode
);

Parameters

hdc

A handle to the device context.

mode

The stretching mode. This parameter can be one of the following values.

Value Meaning
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 Value

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

If the function fails, the return value is zero.

This function can return the following value.

Return code Description
ERROR_INVALID_PARAMETER
One or more of the input parameters is invalid.

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 is slower and requires more processing of the source image than the other three modes; 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

   
Windows version Windows 2000 Professional [desktop apps only] Windows 2000 Server [desktop apps only]
Target Platform Windows
Header wingdi.h (include Windows.h)
Library Gdi32.lib
DLL Gdi32.dll

See Also

Bitmap Functions

Bitmaps Overview

GetStretchBltMode

SetBrushOrgEx

StretchBlt