L_ScrambleBitmap

#include "l_bitmap.h"

L_INT EXT_FUNCTION L_ScrambleBitmap(pBitmap, nColStart, nRowStart nWidth, nHeight, uKey, uFlags)

pBITMAPHANDLE pBitmap;	/* pointer to a bitmap handle for the bitmap to be scrambled */ .
L_INT32 nColStart;	/* starting column in pixels (0-based) */
L_INT32 nRowStart;	/* starting row in pixels (0-based) */
L_INT32 nWidth;	/* width of area to scramble in pixels */
L_INT32 nHeight;	/* height of area to scramble in pixels */
L_INT32 uKey;	/* key that determines the scramble */
L_UINT uFlags;	/* flag that determines whether to encrypt or decrypt the area. */

Scrambles all or a portion of a bitmap. This function is available in the Document/Medical Toolkits.

Parameter	Description
pBitmap	Pointer to a bitmap handle for the bitmap to be scrambled.
nColStart	Starting column in pixels (0-based).
nRowStart	Starting row in pixels (0-based).
nWidth	Width of area to scramble in pixels.
nHeight	Height of area to scramble in pixels.
uKey	Key that determines the scramble. This is an unsigned integer with a minimum value of 0 and a maximum value of 4294967295 (0xffffffff).
uFlags	Flag that determines whether to encrypt or decrypt the area. Possible values are:
	Value	Meaning
	SB_ENCRYPT	Encrypts the area (the reverse of a decrypt).
	SB_DECRYPT	Decrypts the area (the reverse of an encrypt).

Returns

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

Comments

Scrambling a rectangular area means that the pixels in that area are shuffled around into a pseudo-random location within the area.

Some properties of shuffling:

$image\sqrblit.gif$ No colors are introduced,

$image\sqrblit.gif$ Color counts remain unchanged

Given the same encrypt area (defined by nColStart, nRowStart, nWidth, nHeight) and the same key, setting (uFlags = SB_ENCRYPT) is the inverse of (uFlags = SB_DECRYPT)

Required DLLs and Libraries

LTANN

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, Windows CE.

See Also

Functions:	L_AnnGetMetafile, L_AnnSetMetafile, L_AnnGetPredefinedMetafile, L_AnnSetPredefinedMetafile, L_AnnEncryptApply, L_AnnSetEncryptOptions, L_AnnGetEncryptOptions
Topics:	Annotation Functions: Object Properties
	Annotation Objects - Default Values
	Annotation Objects - Automated Features
	Implementing an Automated Annotation Program
	Implementing a Non-automated Annotation Program

Example

// This example scrambles the upper left quadrant of a bitmap
// using the key 123
L_VOID ExampleScrambleBitmap(pBITMAPHANDLE pBitmap)
{
   if (!pBitmap)
      return;

   L_ScrambleBitmap(pBitmap, 0, 0, BITMAPWIDTH(pBitmap)/2, BITMAPHEIGHT(pBitmap)/2, 123, SB_ENCRYPT);
}