Alpha-Trimmed Mean Filter

#include "BIFILTER.H"


HANDLE CALLBACK FilterAlphaTrimmedMean(               HDIB           hDIB,
int           N,
int           P,
int           iShowProgress,
HWND  hParent)


This function will filter the image by the nonlinear alpha-trimmed mean method. This function works for only monochrome, 8 bit per bixel and 24 bit per pixel images. The alpha-timmed mean filter is based on order statistics and varies between a median and a mean filter. It is used when an image contains both short and long tailed types of noise (e.g. both Gaussian and salt and pepper noise). To define the alpha-trimmed mean filter, all pixels surrounding the pixel at the coordinate (x,y) in the image A which are specified by an input N x N size square mask A(i) are ordered from minimum to maximum value. The alpha-trimmed mean filter is given as :


Description: Gauss                                   Description: alpha

The original 256 x 256 pixel image corrupted by additive Gauss noise and the alpha-trimmed mean filtered image using a 5 x 5 pixel square mask and P = 3.




Handle of the DIB to filter.



This parameter specifies the size of the square mask. N cannot be less than 1. See the description and examples above for further information and a possible value.



This parameter specifies the value P in the equation above. P cannot be greater than . See the description and examples above for further information and a possible value.



This parameter specifies the displaying of the progressbar and the preview dialog.

Available values:

DISPLAY_NONE (0)      -     The progressbar and the preview dialog will not display before filtering.

DISPLAY_PROGRESS (1) -The progressbar will display during filtering procedure.

DISPLAY_DIALOG (2) -     The preview dialog will display before filtering. This dialog shows the part of the image before and after filtering.

DISPLAY_BOTH (3)      -     The progressbar and the preview dialog will display.

IMPORTANT: The preview dialog will only display, if there is BiDlgs.dll installed.



Handler of the parent window.

Return values

The handle of the new filtered DIB or NULL if an error occurred.

Programming notes

The function will not free the input DIB.


Header :    Declared in BIFilter.h; include BIFilter.h.

Library :    Use BIFilter.lib.

DLLs :       BIFilter.dll , BIDlgs32.dl.