Smooths the bumps and fills in the nicks of a 1-bit black and white image.


#include "l_bitmap.h"

L_LTIMGCOR_API L_INT L_SmoothBitmap(pBitmap, pSmooth, pfnCallback, pUserData, uFlags)



Pointer to the bitmap handle referencing the bitmap to smooth.

pSMOOTH pSmooth

Pointer to the SMOOTH structure that LEADTOOLS uses to perform the smoothing operation


Optional callback function for additional processing.

If you do not provide a callback function, use NULL as the value of this parameter. If you do provide a callback function, use the function pointer as the value of this parameter.

The callback function must adhere to the function prototype described in SMOOTHCALLBACK Function.

L_VOID *pUserData

Void pointer that you can use to pass one or more additional parameters that the callback function needs.

To use this feature, assign a value to a variable or create a structure that contains as many fields as you need. Then, in this parameter, pass the address of the variable or structure, casting it to L_VOID *. The callback function, which receives the address in its own pUserData parameter, can cast it to a pointer of the appropriate data type to access your variable or structure.

If the additional parameters are not needed, you can pass NULL in this parameter.

L_UINT32 uFlags

Reserved for future use. Must be 0.


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


This function does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this function.

(Document) This function smooths the text in scanned text documents. The behavior of this function can be modified by using its callback.

This function works only on 1-bit black and white images.

If a region is selected, only the selected region will be changed by this function. If no region is selected, the whole image will be processed.

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.

Smooth Function - Before

Smooth Function - Before

Smooth Function - After

Smooth Function - After

View additional platform support for this Smooth function.

Required DLLs and Libraries


Win32, x64, Linux.

See Also




This example smooths all nicks and bumps up to 2 pixels in length
Long bumps/nicks are treated before short bumps/nicks
A LEAD region is returned showing all the changes
A callback is used to display information about bump or nick
The callback does NOT return a region

L_INT  EXT_CALLBACK SmoothCB(L_UINT32  uBumpOrNick, L_INT32   iStartRow, L_INT32   iStartCol, L_INT32   iLength, L_UINT32  uHorV, L_VOID* pUserData) 
   L_TCHAR  szMsg[200]; 
   L_TCHAR* pszBumpOrNick = NULL, * pszHorV = NULL; 
   switch (uBumpOrNick) 
   case SMOOTH_BUMP: 
      pszBumpOrNick = TEXT("Bump"); 
   case SMOOTH_NICK: 
      pszBumpOrNick = TEXT("Nick"); 
      pszHorV = TEXT("Horizontal"); 
      pszHorV = TEXT("Vertical"); 
   //Note: no hRgn to delete because it was not requested 
   wsprintf(szMsg, TEXT("Type[%s]\tRow Col[%d, %d]\tLength[%d]\t[%s]\n"), pszBumpOrNick, iStartRow, iStartCol, iLength, pszHorV); 
   return SUCCESS_REMOVE; 
extern "C" L_INT SmoothBitmapExample(L_VOID) 
   L_INT32        nRet; 
   BITMAPHANDLE   LeadBitmap; 
   BITMAPHANDLE   BitmapRegion; 
   SMOOTH         sm; 
   /* Load the bitmap, keeping the bits per pixel of the file */ 
   nRet = L_LoadBitmap(MAKE_IMAGE_PATH(TEXT("Clean.tif")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if (nRet != SUCCESS) 
      return nRet; 
   memset(&BitmapRegion, 0, sizeof(BITMAPHANDLE)); 
   sm.uStructSize = sizeof(SMOOTH); 
   sm.iLength = 2; 
   sm.pBitmapRegion = &BitmapRegion; 
   sm.uBitmapStructSize = sizeof(BITMAPHANDLE); 
   nRet = L_SmoothBitmap(&LeadBitmap, &sm, SmoothCB, NULL, 0); 
   if (nRet != SUCCESS) 
      return nRet; 
   RECT rectRgn; 
   //Delete the existing region 
   nRet = L_FreeBitmapRgn(&LeadBitmap); 
   if (nRet != SUCCESS) 
      return nRet; 
   nRet = L_GetBitmapRgnBounds(sm.pBitmapRegion, NULL, &rectRgn); 
   if (nRet != SUCCESS) 
      return nRet; 
   if (!IsRectEmpty(&rectRgn)) 
      nRet = L_CopyBitmapHandle(&LeadBitmap, sm.pBitmapRegion, sizeof(BITMAPHANDLE)); 
      if (nRet != SUCCESS) 
         return nRet; 
   return SUCCESS; 

Help Version 22.0.2023.7.11
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LEADTOOLS Raster Imaging C API Help

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© 1991-2023 LEAD Technologies, Inc. All Rights Reserved.