L_CLAHE - Raster Imaging C API Help


#include "l_bitmap.h"

L_LTIMGCOR_API L_INT L_CLAHE(pBitmap0, Alpha, TileSize, nfclipLimit, nBinNumbe, uFlags)


pointer to the bitmap handle

L_FLOAT Alpha;

distribution parameter value

L_UINT TileSize;

Size of tiles

L_FLOAT nfclipLimit;

contrast enhancement limit

L_UINT nBinNumbe;

Number of bins for the histogram

L_UINT uFlags;


Adjusts the image contrast using the Contrast Limited Adaptive Histogram Equalizer (CLAHE) method, Which uses several histograms each corresponding to a distinct section in the image while limiting the amplification of the noise in the image.

Parameter Description
pBitmap0 Pointer to the bitmap handle that references the bitmap to be affected.
Alpha Non-negative real scalar specifying a distribution parameter.
TileSize Positive integer specifying the size of tiles ranging from 1 to 60.
nfclipLimit Real scalar in the range [0, 1] that specifies a contrast enhancement limit. Higher numbers result in more contrast.
nBinNumbe Multiple of 2 integer in the range [2, 1024] that specifies the number of bins for the histogram used in building a contrast enhancing transformation.
uFlags Flags specifying the desired histogram shape for the image tiles. Possible values are:


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


This function supports 8 and 16-bit grayscale images.

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

Topics: Raster Image Functions: Filtering Images


This example loads a bitmap and applies an CLAHE filter.

L_INT CLAHEBitmapExample(L_VOID) 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle to hold the loaded image. */ 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("IMAGE3.dcm")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if(nRet !=SUCCESS) 
      return nRet ; 
   /* Apply a CLAHE filter */ 
   nRet = L_CLAHE(&LeadBitmap, 0.5f, 9, 0.04f, 512, CLAHE_RAYLIEH); 
   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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