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CImage::AlphaBlend 

Displays bitmaps that have transparent or semitransparent pixels.


BOOL AlphaBlend(
   HDC hDestDC,
   int xDest,
   int yDest,
   BYTE bSrcAlpha = 0xff,
   BYTE bBlendOp = AC_SRC_OVER 
) const throw( );
BOOL AlphaBlend(
   HDC hDestDC,
   const POINT& pointDest,
   BYTE bSrcAlpha = 0xff,
   BYTE bBlendOp = AC_SRC_OVER 
) const throw( );
BOOL AlphaBlend(
   HDC hDestDC,
   int xDest,
   int yDest,
   int nDestWidth,
   int nDestHeight,
   int xSrc,
   int ySrc,
   int nSrcWidth,
   int nSrcHeight,
   BYTE bSrcAlpha = 0xff,
   BYTE bBlendOp = AC_SRC_OVER 
);
BOOL AlphaBlend(
   HDC hDestDC,
   const RECT& rectDest,
   const RECT& rectSrc,
   BYTE bSrcAlpha = 0xff,
   BYTE bBlendOp = AC_SRC_OVER 
);

Parameters

hDestDC

Handle to the destination device context.

xDest

The x-coordinate, in logical units, of the upper left corner of the destination rectangle.

yDest

The y-coordinate, in logical units, of the upper left corner of the destination rectangle.

bSrcAlpha

An alpha transparency value to be used on the entire source bitmap. The default 0xff (255) assumes that your image is opaque, and that you want to use per-pixel alpha values only.

bBlendOp

The alpha-blending function for source and destination bitmaps, a global alpha value to be applied to the entire source bitmap, and format information for the source bitmap. The source and destination blend functions are currently limited to AC_SRC_OVER.

pointDest

A reference to a POINT structure that identifies the upper left corner of the destination rectangle, in logical units.

nDestWidth

The width, in logical units, of the destination rectangle.

nDestHeight

The height, in logical units, of the destination rectangle.

xSrc

The logical x-coordinate of the upper left corner of the source rectangle.

ySrc

The logical y-coordinate of the upper left corner of the source rectangle.

nSrcWidth

The width, in logical units, of the source rectangle.

nSrcHeight

The height, in logical units, of the source rectangle.

rectDest

A reference to a RECT structure, identifying the destination.

rectSrc

A reference to a RECT structure, identifying the source.

Nonzero if successful; otherwise 0.

Alpha-blend bitmaps support color blending on a per-pixel basis.

When bBlendOp is set to the default of AC_SRC_OVER, the source bitmap is placed over the destination bitmap based on the alpha values of the source pixels.

This method is applicable to Microsoft Windows 2000, Windows 98, and later systems. See AlphaBlend in the Platform SDK and CImage Limitations with Earlier Operating Systems for more detailed information.

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