Sets up the window-leveling options of a paint or paint and image processing function for a specific bitmap.


#include "l_bitmap.h"

L_LTDIS_API L_INT L_WindowLevel(pBitmap, nLowBit, nHighBit, pLUT, ulLUTLength, uFlags)



Pointer to the bitmap handle referencing the bitmap to be leveled.

L_INT nLowBit

Value indicating the low bit used for leveling. 0 <= nLowBit <= nHighBit <= (11 for 12-bit grayscale or 15 for 16-bit grayscale).

L_INT nHighBit

Value indicating the high bit used for leveling. 0 <= nLowBit <= nHighBit <= (11 for 12-bit grayscale or 15 for 16-bit grayscale).


Optional lookup table that can be used to implement a user defined conversion. For every intensity value between 0 and 2 raised to the power of (nHighBit - nLowBit + 1)-1 there should be a corresponding entry in the lookup table that contains an RGB quad. If pLUT is NULL, the conversion is a normal shift (right or left) and the painted bitmap is 8-bit grayscale. If pLUT is not NULL, the painted bitmap is a 24-bit bitmap.

L_UINT ulLUTLength

Value indicating the number of entries pointed to by pLUT. If pLUT is NULL, then set this to NULL too.

L_UINT uFlags

Value indicating whether pLUT is used by the paint and image processing functions or only by the paint functions. Possible values are:

Value Meaning
WINDOWLEVEL_PAINT [0x00] pLUT is used only by the paint functions.
WINDOWLEVEL_PAINT_AND_PROCESSING [0x01] pLUT is used for both paint and image processing routines.


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


Provides "on demand" window-leveling for a paint functions and does not alter the image data. To convert the image data to a window-leveled bitmap, use L_WindowLevelBitmap.

This function is similar to L_WindowLevelExt, except that it uses an 8-bit per component LUT instead of a 16-bit per component LUT. The 16-bit LUT offers more precision than the 8-bit LUT, so it is better to use L_WindowLevelExt instead of L_WindowLevel.

The 16-bit and 8-bit LUTs are synchronized, which means the LUT applied by L_WindowLevelExt will change the LUT applied with L_WindowLevel and vice versa.

If WINDOW_LEVEL_PAINT_PROCESSING is specified, then all image processing functions will take the pLUT into account.

The BITMAPHANDLE has some members in its structure that are intended for internal use, including pLUT, PaintHighBit and PaintLowBit. These members are useful when window-leveling. For more information about these members, refer to Lookup Table (LUT) in BITMAPHANDLE and its use for Displaying Images and Performing Image Processing topic. More information about the BITMAPHANDLE structure can be found in the LTKRN.H header file, which describes the entire structure.

For information on saving bitmaps that have been window-leveled, refer to Saving Window-Leveled Bitmaps.

Required DLLs and Libraries


Win32, x64, Linux.

See Also




This example sets the window level values for painting and processing the bitmap with a custom palette.

L_INT WindowLevelExample(pBITMAPHANDLE pBitmap) 
   L_INT    nRet; 
   L_UINT32 x; 
   RGBQUAD* ptmp; 
   L_INT    nLowBit; 
   L_INT    nHighBit; 
   L_INT    nLow; 
   L_INT    nHigh; 
   L_UINT32 nSize; 
   /* Change the bitmap to 16-bit grayscale */ 
   nRet = L_GrayScaleBitmap(pBitmap, 16); 
   if (nRet != SUCCESS) 
      return nRet; 
   nRet = L_GetMinMaxBits(pBitmap, &nLowBit, &nHighBit, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
   nRet = L_GetMinMaxVal(pBitmap, &nLow, &nHigh, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
   nSize = (L_UINT32)(1L << (pBitmap->HighBit - pBitmap->LowBit + 1)); 
   pLUT = (RGBQUAD*)GlobalAllocPtr(GHND, nSize * sizeof(RGBQUAD)); 
   ptmp = pLUT; 
   /* fill the first half of the LUT with RED */ 
   for (x = 0; x < nSize / 2; x++) 
      ptmp->rgbRed = 255; 
      ptmp->rgbGreen = 0; 
      ptmp->rgbBlue = 0; 
      ptmp->rgbReserved = 0; 
   /* fill the rest with gray values */ 
   for (x = nSize / 2; x < nSize; x++) 
      ptmp->rgbRed = ((L_UCHAR)((L_UINT32)(x - nLow) * 255 / (nHigh - nLow))); 
      ptmp->rgbGreen = ptmp->rgbRed; 
      ptmp->rgbBlue = ptmp->rgbGreen; 
      ptmp->rgbReserved = 0; 
   nRet = L_WindowLevel(pBitmap, nLowBit, nHighBit, (RGBQUAD*)pLUT, nSize, WINDOWLEVEL_PAINT_AND_PROCESSING); 
   if (nRet != SUCCESS) 
      return nRet; 
   return SUCCESS; 



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LEADTOOLS Raster Imaging C API Help

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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.