#include "l_bitmap.h"

L_LTIMGCLR_API L_INT L_LocalHistoEqualizeBitmap(pBitmap, nWidth, nHeight, nxExt,nyExt, uType, uSmooth, uFlags)


pointer to the bitmap handle

L_INT nWidth;

width of the local histogram equalizer rectangle

L_INT nHeight;

height of the local histogram equalizer rectangle

L_INT nxExt;

width extention

L_INT nyExt;

height extention

L_UINT uType;

color space

L_UINT uSmooth;

smoothing size

L_UINT32 uFlags;


Linearizes the number of pixels locally in a bitmap, based on the specified color space. This can be used to bring out the detail in dark areas of an image, and smooth the edges between blocks.

This function does not support 32-bit grayscale images. It returns the error code ERROR_GRAY32_UNSUPPORTED if a 32-bit grayscale image is passed to this function.

Parameter Description
pBitmap Pointer to the bitmap handle referencing the bitmap to be changed.
nWidth The width of the local histogram equalizer rectangle in pixels. The width should be more than zero.
nHeight The height of the local histogram equalizer rectangle in pixels. The height should be more than zero.
nxExt The extension of the width of the local histogram equalizer rectangle, in pixels.
nyExt The extension of the height of the local histogram equalizer rectangle, in pixels.
uType Flag that indicates which color space to equalize. Possible values are:
  Value Meaning
  RGB_SPACE [0x0001] Linearizes the number of pixels across the RGB color space.(separated channels)
  YUV_SPACE [0x0002] Linearizes the number of pixels across the YUV color space.(Best results)
  GRAY_SPACE [0x0004] Linearizes the number of pixels per gray level in a gray level representation of the image.
uSmooth Size of the area to be used when smoothing the edges between localized blocks. Possible values range from 0 to 7, but if nHeight is less than or equal to 7 then the maximum value for this item is nHeight - 1. If uSmooth = 0 the function will operate without smoothing edges.
uFlags Reserved for future use. Must be 0.



The function was successful.

< 1

An error occurred. Refer to Return Codes.

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_ChangeBitmapIntensity, L_GammaCorrectBitmap, L_ChangeBitmapContrast, L_HistoContrastBitmap, L_StretchBitmapIntensity, L_RemapBitmapIntensity, L_InvertBitmap, L_ChangeBitmapHue, L_ChangeBitmapSaturation, L_FillBitmap, L_GetPixelColor, L_PutPixelColor, L_GetBitmapHistogram, L_WindowLevel, L_AutoColorLevelBitmap, L_ColorLevelBitmap, L_CorrelationBitmap, L_GrayScaleToDuotone, L_GrayScaleToMultitone, L_HolesRemovalBitmapRgn, L_SelectiveColorBitmap, L_SkeletonBitmap, L_DlgLocalHistoEqualize


Raster Image Functions: Modifying Intensity Values


Changing Brightness and Contrast


Raster Image Functions: Changing Brightness and Contrast


For complete sample code, refer to the CHILD.C module of the DEMO example. This example loads a bitmap and applies local histogram equalization.

L_INT LocalHistoEqualizeBitmapExample(L_VOID) 
   L_INT nRet; 
   /* Bitmap handle to hold the loaded image. */ 
   BITMAPHANDLE LeadBitmap; 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("IMAGE1.CMP")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if(nRet !=SUCCESS) 
      return nRet; 
   /* Local Histogram equalize the bitmap */ 
   nRet = L_LocalHistoEqualizeBitmap(&LeadBitmap, 15,15,100,100, YUV_SPACE,2 , 0); 
   if(nRet !=SUCCESS) 
      return nRet; 
   nRet = L_SaveBitmap(MAKE_IMAGE_PATH(TEXT("Result.BMP")), &LeadBitmap, FILE_BMP, 24, 0, NULL); 
   if(nRet !=SUCCESS) 
      return nRet; 
   //free bitmap  
   return SUCCESS; 

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