StretchBlt
The StretchBlt
function copies a bitmap from a source rectangle into a destination rectangle,
stretching or compressing the bitmap to fit the dimensions of the destination
rectangle, if necessary. Windows stretches or compresses the bitmap according
to the stretching mode currently set in the destination device context.
BOOL StretchBlt(
|
HDC hdcDest, |
// handle of destination
device context |
|
int nXOriginDest, |
// x-coordinate of
upper-left corner of dest. rect. |
|
int nYOriginDest, |
// y-coordinate of
upper-left corner of dest. rect. |
|
int nWidthDest, |
// width of
destination rectangle |
|
int nHeightDest, |
// height of
destination rectangle |
|
HDC hdcSrc, |
// handle of source
device context |
|
int nXOriginSrc, |
// x-coordinate of
upper-left corner of source rectangle |
|
int nYOriginSrc, |
// y-coordinate of
upper-left corner of source rectangle |
|
int nWidthSrc, |
// width of source
rectangle |
|
int nHeightSrc, |
// height of source
rectangle |
|
DWORD dwRop |
// raster operation
code |
|
); |
|
Parameters
hdcDest
Identifies
the destination device context.
nXOriginDest
Specifies the
x-coordinate, in logical units, of the upper-left corner of the destination
rectangle.
nYOriginDest
Specifies the
y-coordinate, in logical units, of the upper-left corner of the destination
rectangle.
nWidthDest
Specifies the
width, in logical units, of the destination rectangle.
nHeightDest
Specifies the
height, in logical units, of the destination rectangle.
hdcSrc
Identifies
the source device context.
nXOriginSrc
Specifies the
x-coordinate, in logical units, of the upper-left corner of the source
rectangle.
nYOriginSrc
Specifies the
y-coordinate, in logical units, of the upper-left corner of the source
rectangle.
nWidthSrc
Specifies the
width, in logical units, of the source rectangle.
nHeightSrc
Specifies the
height, in logical units, of the source rectangle.
dwRop
Specifies the
raster operation to be performed. Raster operation codes define how Windows
combines colors in output operations that involve a brush, a source bitmap, and
a destination bitmap.
See the BitBlt
function for a list of common raster operation codes.
Return Values
If the
function succeeds, the return value is nonzero.
If the
function fails, the return value is zero. To get extended error information,
call GetLastError.
Remarks
StretchBlt stretches or compresses the source bitmap in memory
and then copies the result to the destination rectangle. The color data for
pattern or destination pixels is merged after the stretching or compression
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.
If the
specified raster operation requires a brush, Windows uses the brush currently
selected into the destination device context.
The
destination coordinates are transformed by using the transformation currently
specified for the destination device context; the source coordinates are
transformed by using the transformation currently specified for the source
device context.
If the source
transformation has a rotation or shear, an error occurs.
If
destination, source, and pattern bitmaps do not have the same color format, StretchBlt
converts the source and pattern bitmaps to match the destination bitmap.
If StretchBlt
must convert a monochrome bitmap to a color bitmap, it sets white bits (1) to
the background color and black bits (0) to the foreground color. To convert a
color bitmap to a monochrome bitmap, it sets pixels that match the background
color to white (1) and sets all other pixels to black (0). The foreground and
background colors of the device context with color are used.
StretchBlt creates a mirror image of a bitmap if the signs of
the nWidthSrc and nWidthDest parameters or of the nHeightSrc
and nHeightDest parameters differ. If nWidthSrc and nWidthDest
have different signs, the function creates a mirror image of the bitmap along
the x-axis. If nHeightSrc and nHeightDest have different signs,
the function creates a mirror image of the bitmap along the y-axis.
Not all
devices support the StretchBlt function. For more information, see the GetDeviceCaps
function.
See Also