#include "l_bitmap.h"

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


pointer to the bitmap handle

L_INT nLowBit;

low bit to use

L_INT nHighBit;

high bit to use


lookup table

L_UINT ulLUTLength;

number of entries

L_UINT uFlags;


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

Parameter Description
pBitmap Pointer to the bitmap handle referencing the bitmap to be leveled.
nLowBit Value indicating the low bit used for leveling. 0 <= nLowBit <= nHighBit <= (11 for 12-bit grayscale or 15 for 16-bit grayscale).
nHighBit Value indicating the high bit used for leveling. 0 <= nLowBit <= nHighBit <= (11 for 12-bit grayscale or 15 for 16-bit grayscale).
pLUT 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.
ulLUTLength Value indicating the number of entries pointed to by pLUT. If pLUT is NULL, then set this to NULL too.
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.



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


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


Win32, x64, Linux.

See Also


L_WindowLevelExt, L_WindowLevelBitmap, L_WindowLevelBitmapExt, L_PaintDC, L_PaintDCBuffer, L_PaintDCEffect, L_PaintRgnDC, L_WindowLevelFillLUT, L_SelectBitmapData, L_ShiftBitmapData, L_AutoZoneBitmap


Raster Image Functions: Palettes


Raster Image Functions: Displaying and Printing


Color Halftone and Halftone Images


Grayscale Images


Saving Window-Leveled Bitmaps


Raster Image Functions: Processing an Image



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 */ 
      ptmp->rgbRed       = 255; 
      ptmp->rgbGreen     = 0; 
      ptmp->rgbBlue      = 0; 
      ptmp->rgbReserved  = 0; 
   /* fill the rest with gray values */ 
      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, 
   if(nRet != SUCCESS) 
      return nRet; 
   return SUCCESS; 



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