DrvStretchBlt

BOOL DrvStretchBlt(

IN SURFOBJ *psoDest,
IN SURFOBJ *psoSrc,
IN SURFOBJ *psoMask,
IN CLIPOBJ *pco,
IN XLATEOBJ *pxlo,
IN COLORADJUSTMENT *pca,
IN POINTL *pptlHTOrg,
IN RECTL *prclDest,
IN RECTL *prclSrc,
IN POINTL *pptlMask,
IN ULONG iMode
);

DrvStretchBlt provides stretching bit-block transfer capabilities between any combination of device-managed and GDI-managed surfaces. This function enables the device driver to write to GDI bitmaps, especially when the driver can do halftoning. This function allows the same halftoning algorithm to be applied to GDI bitmaps and device surfaces.

Parameters

psoDest

Points to a SURFOBJ that identifies the surface on which to draw.

psoSrc

Points to a SURFOBJ that defines the source for the bit-block transfer operation.

psoMask

This optional parameter points to a surface that provides a mask for the source. The mask is defined by a logic map, which is a bitmap with 1 bit per pixel.

The mask limits the area of the source that is copied. If this parameter is specified, it has an implicit rop4 of 0xCCAA, meaning the source should be copied wherever the mask is one, but the destination should be left alone wherever the mask is zero.

When this parameter is null there is an implicit rop4 of 0xCCCC, which means that the source should be copied everywhere in the source rectangle.

The mask will always be large enough to contain the relevant source; tiling is unnecessary.

pco

Points to a CLIPOBJ that limits the area to be modified in the destination. GDI services are provided to enumerate the clip region as a set of rectangles.

Whenever possible, GDI simplifies the clipping involved. However, unlike DrvBitBlt, DrvStretchBlt can be called with a single clipping rectangle. This prevents rounding errors in clipping the output.

pxlo

Points to a XLATEOBJ that specifies how color indices are to be translated between the source and target surfaces.

The XLATEOBJ can also be queried to find the RGB color for any source index. A high quality stretching bit-block transfer will need to interpolate colors in some cases.

pca

Points to a COLORADJUSTMENT structure that defines the color adjustment values to be applied to the source bitmap before stretching the bits. (See the Win32 SDK.)

pptlHTOrg

Specifies the origin of the halftone brush. Device drivers that use halftone brushes should align the upper left pixel of the brush’s pattern with this point on the device surface.

prclDest

Points to a RECTL structure that defines the area to be modified in the coordinate system of the destination surface. This rectangle is defined by two points that are not necessarily well ordered, meaning the coordinates of the second point are not necessarily larger than those of the first point. The rectangle they describe does not include the lower and right edges. This function is never called with an empty destination rectangle.

DrvStretchBlt can do inversions of x and y when the destination rectangle is not well ordered.

prclSrc

Points to a RECTL that defines the area that will be copied in the coordinate system of the source surface. The rectangle is defined by two points, and will map onto the rectangle defined by prclDest. The points of the source rectangle are well ordered. This function is never given an empty source rectangle.

The mapping is defined by prclSrc and prclDest. The points specified in prclDest and prclSrc lie on integer coordinates, which correspond to pixel centers. A rectangle defined by two such points is considered to be a geometric rectangle with two vertices whose coordinates are the given points, but with 0.5 subtracted from each coordinate. (POINTL structures should be considered a shorthand notation for specifying these fractional coordinate vertices.)

The edges of any rectangle never intersect a pixel, but go around a set of pixels. The pixels inside the rectangle are those expected for a “bottom-right exclusive” rectangle. DrvStretchBlt will map the geometric source rectangle exactly onto the geometric destination rectangle.

pptlMask

Points to a POINTL structure that specifies which pixel in the given mask corresponds to the upper left pixel in the source rectangle. Ignore this parameter if no mask is specified.

iMode

Specifies how source pixels are combined to get output pixels. The HALFTONE mode is slower than the other modes, but produces higher quality images.

Value	Meaning
WHITEONBLACK	On a shrinking bit-block transfer, pixels should be combined with a Boolean OR operation. On a stretching bit-block transfer, pixels should be replicated.
BLACKONWHITE	On a shrinking bit-block transfer, pixels should be combined with a Boolean AND operation. On a stretching bit-block transfer, pixels should be replicated.
COLORONCOLOR	On a shrinking bit-block transfer, enough pixels should be ignored so that pixels don’t need to be combined. On a stretching bit-block transfer, pixels should be replicated.
HALFTONE	The driver can use groups of pixels in the output surface to best approximate the color or gray level of the input.

Return Value

The return value is TRUE if the function is successful. Otherwise, it is FALSE, and an error code is logged.

Comments

This function can be provided to handle only certain forms of stretching, such as by integer multiples. If the driver has hooked the call and is asked to perform an operation it does not support, the driver should forward the data to EngStretchBlt for GDI to handle.

If the driver wants GDI to handle halftoning, and wants to ensure the proper iMode value, the driver can hook DrvStretchBlt, set iMode to HALFTONE, and call back to GDI with EngStretchBlt with the set iMode value.

DrvStretchBlt is optional for display drivers.

See Also

CLIPOBJ, DrvBitBlt, EngStretchBlt, SURFOBJ, XLATEOBJ