#include "ltwrappr.h"

virtual L_INT LBitmap::FrqFilterMask(pFTArray, bOnOff, uFlags = 0)


pointer to structure

L_BOOL bOnOff;


L_UINT32 uFlags;


Creates a mask filter to remove specific frequency components from a bitmap.

Parameter Description
pFTArray Pointer to an FTARRAY structure. The acxData field is a two-dimensional array holding the frequency components.
bOnOff Value that indicates whether the frequency components are removed if the corresponding pixel value is zero. Possible values are:
  Value Meaning
  TRUE If the pixel value equals zero the frequency components in its location in acxData will be removed, otherwise no change. A component is "removed" when both members of the corresponding L_COMPLEX structure are set to 0.
  FALSE The frequency component in the pixel location in acxData will be multiplied by the value of the pixel divided by 255.
uFlags Reserved for future use. Must be 0.



The function was successful.

< 1

An error occurred. Refer to Return Codes.


This function is used only when you are dealing with Fourier Transform functions.

The Mask bitmap will be treated as grayscale bitmap. The (0,0) frequency located in mask bitmap center; positive X harmonics located in the right half of the mask bitmap and positive Y harmonics located in the lower half of the mask bitmap. Mask bitmaps dimensions must be equal to acxDatas dimensions.

To update a status bar or detect a user interrupt during execution of this function, refer to LBase::EnableStatusCallback.

This function does not support 12 and 16-bit grayscale and 48 and 64-bit color images. If the image is 12 and 16-bit grayscale and 48 and 64-bit color, the function will not return an error.

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.

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.

See Also


LBitmap::Fragment, LBitmap::HighPassFilter, LBitmap::UnsharpMask, LBitmap::AverageFilter, LBitmap::MedianFilter, LBitmap::AddNoise, LBitmap::IntensityDetect, LBitmap::SpatialFilter, LBitmap::BinaryFilter, LBitmap::MaxFilter, LBitmap::MinFilter, LBitmap::AddShadow, LBitmap::AllocFTArray, LBitmap::ChangeHueSatInt, LBitmap::ColorReplace, LBitmap::ColorThreshold, LBitmap::DFT, LBitmap::DirectionEdgeStatistical, LBitmap::FFT, LBitmap::FreeFTArray, LBitmap::FrqFilter, LBitmap::FTDisplay, LBitmap::GetStatisticsInfo, LBitmap::GetFeretsDiameter, LBitmap::GetObjectInfo, LBitmap::GetRgnContourPoints, LBitmap::GetRgnPerimeterLength, LBitmap::MathFunction, LBitmap::RevEffect, LBitmap::Segment, LBitmap::SubtractBackground, LBitmap::UserFilter, LBitmap::DirectionEdgeStatistical2


Raster Image Functions: Fourier Transform Functions


Removing Noise


Raster Image Functions: Removing Noise


L_INT LBitmap__FrqFilterMaskExample(LBitmap *pLeadBitmap, LBitmap *pMaskBitmap, pFTARRAY pFTArray)  
   L_INT nRet; 
   RECT rect; 
   /* Assume acxData field of pFTArray is the correct size*/ 
   /* apply DFT*/ 
   nRet =pLeadBitmap->DFT (pFTArray, &rect, DFT_DFT | DFT_GRAY|DFT_RANGE| DFT_INSIDE_X| DFT_OUTSIDE_Y); 
   if(nRet !=SUCCESS) 
      return nRet; 
   /* filter frequencies */ 
   nRet =pMaskBitmap->FrqFilterMask( pFTArray, TRUE); 
   if(nRet !=SUCCESS) 
      return nRet; 
   /* apply inverse DFT */ 
   /* After this call, the image should be clean */ 
   if(nRet !=SUCCESS) 
      return nRet; 
   return SUCCESS; 
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