#include "l_bitmap.h"

L_LTIMGEFX_API L_INT L_HighPassFilterBitmap(pBitmap, uRadius, uOpacity, uFlags)


pointer to the bitmap handle

L_UINT uRadius;

radius of the neighborhood

L_UINT uOpacity;


L_UINT32 uFlags;


Removes low frequency details in a bitmap, resulting in a sharpened image.




Pointer to the bitmap handle that references the bitmap to which to apply the filter.


Value greater than 0 that indicates the radius of the neighborhood on which the filter is applied, in pixels.


Value that represents the intensity of the effect. The valid range is from 0 to 100. At 100, only the object outlines remain.


Reserved for future use. Must be 0.



The function was successful.

< 1

An error occurred. Refer to Return Codes.


This filter removes low-frequency detail in the bitmap. The effect is opposite to that of the Gaussian Blur filter (L_GaussianFilterBitmap).

To increase the thickness of the edges, increase the value of uRadius. Usually a low value for uRadius is better.

Unlike the L_UnsharpMaskBitmap function, when using this function image noise is not increased.

For an example, click here

If the bitmap has a region, the effect will be applied on the region only.

This function supports 12- and 16-bit grayscale and 48- and 64-bit color images. Support for 12- and 16-bit grayscale and 48- and 64-bit color images is available in the Document and Medical Imaging toolkits.

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

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, Linux.

See Also


L_SharpenBitmap, L_PosterizeBitmap, L_MosaicBitmap, L_EmbossBitmap, L_MedianFilterBitmap, L_AddBitmapNoise, L_IntensityDetectBitmap, L_SpatialFilterBitmap, L_BinaryFilterBitmap, L_SolarizeBitmap, L_WindowLevel, L_UnsharpMaskBitmap, L_GaussianFilterBitmap


Raster Image Functions: Filtering Images


Removing Noise


Detecting and Enhancing Edges and Lines


Raster Image Functions: Detecting and Enhancing Edges and Lines


L_INT HighPassFilterBitmapExample(L_VOID) 
   L_INT nRet; 
   BITMAPHANDLE LeadBitmap;   /* Bitmap handle for the image */ 
   /* Load a bitmap at its own bits per pixel  */ 
   nRet = L_LoadBitmap (MAKE_IMAGE_PATH(TEXT("sample5.cmp")), &LeadBitmap, sizeof(BITMAPHANDLE), 0, ORDER_BGR, NULL, NULL); 
   if(nRet !=SUCCESS) 
      return nRet; 
   /*Sharpen image by applying the high pass filter*/ 
   nRet = L_HighPassFilterBitmap(&LeadBitmap, 10, 100, 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  
   return SUCCESS; 
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