In This Topic ▼

L_LocalHistoEqualizeBitmap

Summary

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.

Syntax

#include "l_bitmap.h"

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

Parameters

pBITMAPHANDLE pBitmap

Pointer to the bitmap handle referencing the bitmap to be changed.

L_INT nWidth

The width of the local histogram equalizer rectangle in pixels. The width should be more than zero.

L_INT nHeight

The height of the local histogram equalizer rectangle in pixels. The height should be more than zero.

L_INT nxExt

The extension of the width of the local histogram equalizer rectangle, in pixels.

L_INT nyExt

The extension of the height of the local histogram equalizer rectangle, in pixels.

L_UINT 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.

L_UINT 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.

L_UINT32 uFlags

Reserved for future use. Must be 0.

Returns

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

Local Equalize Function - Before

Local Equalize Function - After

View additional platform support for this Local Equalize function.

Required DLLs and Libraries

LTIMGCLR
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, Linux.

Example

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 
   if(LeadBitmap.Flags.Allocated) 
      L_FreeBitmap(&LeadBitmap); 
 
   return SUCCESS; 
}