Filters the bitmap based on a user-defined filter / mask. This function is similar to the spatial and binary filter functions.


#include "ltwrappr.h"

virtual L_INT LBitmap::UserFilter(pFilter, uFlags = 0)


pUSERFLT pFilter

Pointer to an LPUSERFLT structure that contains information about the mask to be applied.

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.


With this function you can create a user-defined filter and apply it to the image. The selected filter is passed as a parameter to this function. The filter has a rectangular form (matrix) where the values are user-defined. It allows the creation of simple customized filters, where each value found in matrix is multiplied by the corresponding pixel, and then the specified operation is performed on the results.

Support for 12 and 16-bit grayscale and 48 and 64-bit color images is available only in the Document/Medical toolkits.

When the filter is applied to pixels from the edge and you choose the sum operation, the edge rows and columns are duplicated. For example, if the pixel (-1, 5) is needed, the pixel (0, 5) is used instead.

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.

User Filter Function - Before

User Filter Function - Before

User Filter Function - After

User Filter Function - After

View additional platform support for this User Filter function.

Required DLLs and Libraries


Win32, x64.

See Also




L_INT LBitmap__UserFilterExample(LBitmap *pLeadBitmap)  
   L_INT nRet; 
   /*In this example the high pass filter will be applied using user defined matrix*/ 
   pUSERFLT  pFilter;  
   L_INT  i, j;  
   /* Allocate the user filter structure. And also we need a (3x3) matrix with 9 elements. */ 
   pFilter = (pUSERFLT)malloc(sizeof(USERFLT) + 9 * sizeof(L_INT));  
   /* Initialize the array with factor used to apply the high pass filter */ 
   for(i = 0; i < 3; i++) 
      for(j = 0; j < 3; j++) 
         if(j == 1 || i == 1)  
            if(j == 1 && i == 1)  
               pFilter->ufltMatrix[i * 3 + j] = 5;  
               pFilter->ufltMatrix[i * 3 + j] = -1;  
         else  pFilter->ufltMatrix[i * 3 + j] = 0;  
   pFilter->uStructSize  = sizeof(USERFLT);  
   pFilter->ufltWidth  = 3;  
   pFilter->ufltHeight = 3;  
   pFilter->ufltCenter.x = 1;  
   pFilter->ufltCenter.y = 1;  
   pFilter->ufltDivisor  = 1;  
   pFilter->nfltOffset  = 0;  
   pFilter->ufltFlag  = UD_SUM;  
   /* Apply the high pass custom filter */ 
   nRet =pLeadBitmap->UserFilter (pFilter); 
   if(nRet !=SUCCESS) 
      return nRet; 
   /* Free the filter */ 
   return SUCCESS; 
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