|
||
class TGopBitBltAlphaBitmap : public TGraphicsOperation;
An accelerated graphics operation that copies a rectangular region of one bitmap into another using alpha blending values provided in a third bitmap.
The way alpha blending works is as follows: if the alpha value is the maximum, the source pixel is opaque, in other words, the full colour of the pixel is written to the destination. If the alpha value is zero, the source pixel is fully transparent, and the destination is left unaltered. Values in-between cause blending with the following formula:
Destination = Source*Alpha/max_Alpha + Destination*(max_Alpha-Alpha)/max_Alpha
Colour alpha-bitmaps specify red, green and blue alpha values for each pixel, greyscale bitmaps specify a single alpha value for each pixel. The maximum alpha value depends on the bitmap's display mode. For example, 255 is the maximum for an EGray256 or EColor16M bitmap. The maximum is less for bitmaps which use fewer bits per colour component.
Supported bitmap formats than can be used as alpha bitmaps are given in TGraphicsAcceleratorCaps::iAlphaBitmap
.
Objects of this class can be passed to a graphics accelerator's Operation() function either individually, or in a buffer.
TGraphicsOperation
- Abstract base class for all graphics operations.
TGopBitBltAlphaBitmap
- An accelerated graphics operation that copies a rectangular region of one bitmap...
Defined in TGopBitBltAlphaBitmap
:
TGopBitBltAlphaBitmap(const TPoint &,TAcceleratedBitmapSpec,TRect &,TAcceleratedBitmapSpec)
Constructor with a position, two bitmap specs and a rectangle. iAlphaBitmap
A handle to the alpha bitmap, the bitmap that contains alpha blending values. iDestination
The destination for the top left hand corner of the portion of the source bitmap...iSourceBitmap
A handle to the source bitmap, and other information needed to access it. iSourceRect
A rectangle defining the part of the source bitmap to be copied. Inherited from TGraphicsOperation
:
Append(TInt,TAny *)
EAlphaBlendOneBitmap
EAlphaBlendTwoBitmaps
EBitBlt
EBitBltAlphaBitmap
EBitBltAlphaChannel
EBitBltMasked
EBitBltTransparent
EChunkTest
EFadeRect
EFilledPolygon
EFilledPolygonWithPattern
EFilledRect
EFilledRectUsingDrawMode
EFilledRectWithPattern
EInvertRect
EScaledBitBlt
EScaledBitBltAlphaBitmap
EScaledBitBltAlphaChannel
EScaledBitBltMasked
EScaledBitBltTransparent
EVirtualAddressTest
Function()const
Next()const
Size()const
TGopFunction
TGraphicsOperation(TGopFunction,TInt)
iFunction
iSize
TGraphicsAcceleratorCaps::iAlphaBitmap
Specifies the supported alpha bitmap types. Uses a bit flag for each TAlphaBitma...inline TGopBitBltAlphaBitmap(const TPoint &aDestination, TAcceleratedBitmapSpec aSourceBitmap, TRect &aSourceRect, TAcceleratedBitmapSpec
aAlphaBitmap);
Constructor with a position, two bitmap specs and a rectangle.
|
TPoint iDestination;
The destination for the top left hand corner of the portion of the source bitmap.
TAcceleratedBitmapSpec iSourceBitmap;
A handle to the source bitmap, and other information needed to access it.
TAcceleratedBitmapSpec iAlphaBitmap;
A handle to the alpha bitmap, the bitmap that contains alpha blending values.