L_ScrambleBitmap

#include "l_bitmap.h"

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

Scrambles all or a portion of a bitmap.

Parameters

pBITMAPHANDLE pBitmap

Pointer to a bitmap handle for the bitmap to be scrambled.

L_INT nColStart

Starting column in pixels (0-based).

L_INT nRowStart

Starting row in pixels (0-based).

L_INT nWidth

Width of area to scramble in pixels.

L_INT nHeight

Height of area to scramble in pixels.

L_UINT uKey

Key that determines the scramble. This is an unsigned integer with a minimum value of 0 and a maximum value of 4294967295 (0xffffffff).

L_UINT 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).
SB_INTERSECT Intersect the specified rectangle with the bitmaps rectangle.

Returns

Value Meaning
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:

No colors are introduced,

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

Platforms

Win32, x64, Linux.

See Also

Functions

Topics

Example

This example scrambles the upper left quadrant of a bitmap using the key 123

L_INT ScrambleBitmapExample(pBITMAPHANDLE pBitmap) 
{ 
   L_INT nRet; 
 
   if (!pBitmap) 
      return ERROR_NO_BITMAP; 
 
   nRet = L_ScrambleBitmap(pBitmap, 0, 0, BITMAPWIDTH(pBitmap)/2, BITMAPHEIGHT(pBitmap)/2, 123, SB_ENCRYPT); 
   if(nRet != SUCCESS) 
      return nRet; 
   return SUCCESS; 
} 

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