Function GraBitBlt() Foundation
Copies section of a raster image into a presentation space (bit-blitting).
GraBitBlt( [<oTargetPS>], ; [<oSourcePS>], ; <aTargetRect>, ; <aSourceRect>, ; [<nRasterOP>], ; [<nCompress>] ) --> lSuccess
The return value of GraBitBlt() is .T. (true) if the raster image was copied from the specified area in <oSourcePS> to <oTargetPS>, otherwise it is .F. (false). If the return value is equal to .F., the cause of the error can be determined using GraError().
The function GraBitBlt() is an efficient function for copying raster images (bitmaps). Unlike a vector image which consists of vector-based shapes, a raster image contains all the pixels that make up the image.
GraBitBlt() operations are very fast. Using GraBitBlt(), sections of raster images (bitmaps) are copied, enlargements and reductions are produced and multiple copies of a raster image are displayed very quickly. For example, a window background might be filled with a fill pattern defined in a bitmap file and copied repeatedly to fill the window.
Raster images cannot be scaled without loss of information. Enlarging a bitmap causes individual pixels to be expanded, which introduces jagged edges that become more pronounced with increasing scale factors. Similarly, reducing an image in size causes pixels to be eliminated and hence color information to be lost. GraBitBlt() supports several modes which affect the way eliminated pixels are treated during image reduction. The desired compression mode is selected using the <nCompress> parameter.
The function GraBitBlt() can copy a raster image within a single presentation space or from one presentation space into another. If, for example, the second presentation space <oTarget> is associated with a printer, raster images are printed using GraBitBlt(). More information on the display and output of raster images is found with the class XbpBitmap().
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