L_GetBitmapAlpha

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_GetBitmapAlpha(pBitmap, pAlpha, uStructSize)

pBITMAPHANDLE pBitmap;	/* points to the source bitmap handle */
pBITMAPHANDLE pAlpha;	/* points to the destination bitmap handle */
L_UINT uStructSize;	/* size in bytes, of the structure pointed to by pAlpha */

Creates a grayscale bitmap from the source bitmap's alpha channel data.

Parameter	Description
pBitmap	Points to the source bitmap handle.
pAlpha	Points to the destination bitmap handle to hold the alpha channel data.
uStructSize	Size in bytes, of the structure pointed to by pAlpha, for versioning. Use sizeof(BITMAPHANDLE).

Returns

SUCCESS	The function was successful.
< 1	An error occurred. Refer to Return Codes.

Comments

Only 16-, 32-, and 64-bit images can have an alpha channel. If the source bitmap has another color resolution, the result is an image filled with zeros.

Typically, the alpha channel contains a mask that is used for transparency, as shown in the example for L_SetBitmapAlpha.

This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

Required DLLs and Libraries

LTKRN

For a listing of the exact DLLs and Libraries needed, based on the toolkit version, refer to Files To Be Included With Your Application.

Platforms

Windows 95 / 98 / Me, Windows 2000 / XP.

Functions:	L_SetBitmapAlpha, L_CreateMaskFromBitmapRgn, L_SetBitmapRgnFromMask
Topics:	Defining and Using a Bitmap Region
	Color Halftone and Halftone Images
	Saving a Region