**Description** This function will find edges on the input image by the Marr-Hildreth edge detection method. This function works for 8 and 24 bit per pixel images. Marr-Hildreth edge-detection first filters the image with the Laplacian of the Gaussian filter matrix, wich is computed by the standard deviation value input. The value of standard deviation determines the width of the filter matrix, and controls the amount of smoothing produced by the Gaussian component. The Laplacian of the Gaussian filtering will smooth the image and enhance the edges. After filtering edge localization is processed by finding zero crossings at each pixel for all directions.

**Examples**

** **

The original 500 x 400 pixel image and the Marr-Hildreth edge detected image with fSTDV = 2.0, bStirctEdge = TRUE and bMeanGauss = FALSE parameter values.

**Syntax** RetVal = [*BiFilter.*]**FilterEdgeMH** hDib fSTDV bStrictEdge bMeanGauss bShowDialog

**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.

** fSTDV ** double Standard deviation value. The value of standard deviation determines the width of the filter matrix, and controls the amount of smoothing produced by the Gaussian component. STDV cannot be less than 0. See the description and examples above for further information and a possible value.

** bStrictEdge ** BOOL** ** This parameter specifies the strictness of edge detection. If it’s **TRUE**, less but stronger edges will be found. It’s important that in case of strict edges, it can be possible that no edges will be appeared. If does, choose a larger STDV value.

** bMeanGauss ** BOOL If this parameter is turned on, a smoothed Gaussian kernel will be used during the convolution, and less edges will be found, but a cleaner image will be produced.

** bShowDialog ** BOOL This parameter specifies the displaying of the preview dialog. IMPORTANT: The preview dialog will only display, if there is BiDlgs.dll installed

**See Also**