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LBitmap::CLAHE

Summary

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.

Syntax

#include "ltwrappr.h"

virtual L_INT LBitmap::CLAHE(Alpha, TileSize, nfclipLimit, nx, uFlags)

Parameters

L_FLOAT Alpha

Non-negative real scalar specifying a distribution parameter.

L_UINT TileSize

Positive integer specifying the size of tiles ranging from 1 to 60.

float nfclipLimit

Real scalar in the range [0, 1] that specifies a contrast enhancement limit. Higher numbers result in more contrast.

L_UINT nx

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.

L_UINT uFlags

Flags specifying the desired histogram shape for the image tiles. Possible values are:

CLAHE_RAYLIEH
CLAHE_EXPONENTIAL
CLAHE_NORMAL
CLAHE_SIGMOID
CLAHE_RETURN8BITIMAGE
CLAHE_RETURN16BITIMAGE

Returns

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

Comments

This function supports 8 and 16-bit grayscale images.

Required DLLs and Libraries

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

Platforms

Win32, x64.

Example

This example loads a bitmap and applies an CLAHE filter.

L_INT LBitmap__CLAHEBitmapExample(L_VOID) 
{ 
    L_INT nRet ; 
    LBitmap LeadBitmap ; 
 
    nRet = LeadBitmap.Load(MAKE_IMAGE_PATH(TEXT("IMAGE3.dcm")), 0,ORDER_BGR); 
    if(nRet != SUCCESS) 
        return nRet ; 
 
   /* Apply a CLAHE filter */ 
   nRet = LeadBitmap.CLAHE(0.5f, 9, 0.04f, 512, CLAHE_RAYLIEH); 
   if(nRet !=SUCCESS) 
      return nRet; 
 
   return SUCCESS; 
}