The TransparentBlt function performs a bit-block transfer of the color data corresponding to a rectangle of pixels from the specified source device context into a destination device context.

BOOL TransparentBlt(
  HDC hdcDest,        // handle to destination DC
  int nXOriginDest,   // x-coord of destination upper-left corner
  int nYOriginDest,   // y-coord of destination upper-left corner
  int nWidthDest,     // width of destination rectangle
  int hHeightDest,    // height of destination rectangle
  HDC hdcSrc,         // handle to source DC
  int nXOriginSrc,    // x-coord of source upper-left corner
  int nYOriginSrc,    // y-coord of source upper-left corner
  int nWidthSrc,      // width of source rectangle
  int nHeightSrc,     // height of source rectangle
  UINT crTransparent  // color to make transparent
);

Parameters

hdcDest

[in] Handle to the destination device context.

nXOriginDest

[in] Specifies the x-coordinate, in logical units, of the upper-left corner of the destination rectangle.

nYOriginDest

[in] Specifies the y-coordinate, in logical units, of the upper-left corner of the destination rectangle.

nWidthDest

[in] Specifies the width, in logical units, of the destination rectangle.

hHeightDest

[in] Handle to the height, in logical units, of the destination rectangle.

hdcSrc

[in] Handle to the source device context.

nXOriginSrc

[in] Specifies the x-coordinate, in logical units, of the source rectangle.

nYOriginSrc

[in] Specifies the y-coordinate, in logical units, of the source rectangle.

nWidthSrc

[in] Specifies the width, in logical units, of the source rectangle.

nHeightSrc

[in] Specifies the height, in logical units, of the source rectangle.

crTransparent

[in] The RGB color in the source bitmap to treat as transparent.

Return Values

If the function succeeds, the return value is TRUE.

If the function fails, the return value is FALSE.

Windows NT/2000/XP: To get extended error information, call GetLastError.

Remarks

The TransparentBlt function works with compatible bitmaps (DDBs).

The TransparentBlt function supports all formats of source bitmaps. However, for 32 bpp bitmaps, it just copies the alpha value over. Use AlphaBlend to specify 32 bits-per-pixel bitmaps with transparency.

If the source and destination rectangles are not the same size, the source bitmap is stretched to match the destination rectangle. When the SetStretchBltMode function is used, the iStretchMode modes of BLACKONWHITE and WHITEONBLACK are converted to COLORONCOLOR for the TransparentBlt function.

The destination device context specifies the transformation type for the destination coordinates. The source device context specifies the transformation type for the source coordinates.

TransparentBlt does not mirror a bitmap if either the width or height, of either the source or destination, is negative.

Windows 95/98: TransparentBlt contains a memory leak that can exhaust system resources. To draw a transparent bitmap using BitBlt, see Knowledge Base article 79212.

Windows 98/Me, Windows 2000/XP: When used in a multiple monitor system, both hdcSrc and hdcDest must refer to the same device or the function will fail. To transfer data between DCs for different devices, convert the memory bitmap to a DIB by calling GetDIBits. To display the DIB to the second device, call SetDIBits or StretchDIBits.

Requirements

  Windows NT/2000/XP/Vista: Included in Windows 2000 and later.
  Windows 95/98/Me: Included in Windows 98 and later.
  Header: Declared in Wingdi.h; include Windows.h.
  Library: Use Msimg32.lib.

See Also

Bitmaps Overview, Bitmap Functions, AlphaBlend, GetDIBits, SetDIBits, SetStretchBltMode, StretchDIBits