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


#include "l_bitmap.h"

L_LTDIS_API L_INT L_WindowLevelExt (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 L_RGBQUAD16 entry. 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 16-bit grayscale or 48-bit bitmap (depending on whether the LUT contains only grayscale entries or whether it has color entries as well).

L_UINT ulLUTLength

Value indicating the number of entries pointed to by pLUT. If pLUT is NULL, then set this to 0 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 the paint functions and does not alter the image data. To convert the image data to a window-leveled bitmap, use L_WindowLevelBitmapExt.

This function is similar to L_WindowLevel, except that it uses 16-bit per component LUT instead of 8-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.

LEADTOOLS supports two types of LUTs for 10-16-bit grayscale images (8-bit LUT and 16-bit LUT). Typical grayscale image display and processing is done using an 8-bit LUT. But, you can also use a 16-bit LUT, which offers more precision. Some special video cards and monitors also support display of grayscale images using a 16-bit LUT.

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 that are useful when window-leveling. For more information about these members, used when displaying images or performing image processing, refer to Lookup Table (LUT) in BITMAPHANDLE and its use for Displaying Images and Performing Image Processing. If necessary, you can refer to 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 WindowLevelExtExample(pBITMAPHANDLE pBitmap) 
   L_INT          nRet; 
   L_UINT32       x; 
   L_RGBQUAD16*   ptmp; 
   L_RGBQUAD16*   pLUT; 
   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 = (L_RGBQUAD16*)GlobalAllocPtr(GHND, nSize * sizeof(L_RGBQUAD16)); 
   ptmp = pLUT; 
   /* fill the first half of the LUT with RED */ 
   for (x = 0; x < nSize / 2; x++) 
      ptmp->rgbRed = 0xFFFF; 
      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_UINT16)((L_UINT32)(x - nLow) * 0xFFFF / (nHigh - nLow))); 
      ptmp->rgbGreen = ptmp->rgbRed; 
      ptmp->rgbBlue = ptmp->rgbGreen; 
      ptmp->rgbReserved = 0; 
   nRet = L_WindowLevelExt(pBitmap, nLowBit, nHighBit, 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.