**Description** This function will filter the image by the nonlinear geometric mean method. This function works for only monochrome, 8 bit per pixel and 24 bit per pixel images. The geometric mean filter is member of a set of nonlinear mean filters, which are better at removing Gaussian type noise and preserving edge features than the arithmetic mean filter. The geometric mean filter is very susceptible to negative outliers. The definition of geometric mean filter is:

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where the coordinate (x+i, y+j ) is defined over the image A and the coordinate (i j) is defined over the N x N size square mask.

**Examples**

**Syntax** RetVal = [*BiFilter.*]**FilterGeometricMean** hDib N iShowProgress hWnd

**Returns RetVal ** LONGLONG The handle of new filtered DIB, 0 if an error occurred, or -1 if the BIFilter.dll does not installed.

**Remarks hDib ** LONGLONG Handle of the image to filter.

** N ** short 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.

** iShowProgress ** short 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 BIDlgs32.dll installed.

** hWnd ** LONGLONG Handler of the parent window.

**See Also**