FSHARP -- Sharpening Filter (up to 33x33)

Performs an edge sharpening filter on image data. This filter improves the detail and contrast within an image.

See Also: FAV, FED, FME, FGA, FMO, FPR, FLE, FSOBEL, FPRE

INPUT PORT(S)

Input

Type:	Raster
Connection:	Mandatory
Minimum Layers:	1
Maximum Layers:	1

Contains the input raster layer to be filtered.

Mask

Type:	Bitmap
Connection:	Optional
Minimum Layers:	0
Maximum Layers:	1

Contains the input area mask layer, consisting of a bitmap that indicates which area in the input raster should be processed. If no bitmap is provided, then the entire layer is filtered.

OUTPUT PORT(S)

Output

Type:	Raster
Connection:	Optional
Minimum Layers:	0
Maximum Layers:	1

Contains the output layer, which receives the filtered raster data.

"Output" can be the same as "Input".
Only the area under Mask is written to "Output".

INPUT PARAMETER(S)

FSHARP is controlled by the following parameters:

Filter X Size (Pixels)

Name:	FilterXSize
Type:	Integer
Valid Values:	1 <= x <= 33
Default:	3
Requirement:	Mandatory

Specifies the filter's X size in units of pixels.

Notes:

The size entered must be an odd integer between 1 and 33, inclusive.
It must not exceed the database size.
The X size can be different from the Y size (i.e., the filter does not have to be square).

Filter Y Size (Lines)

Name:	FilterYSize
Type:	Integer
Valid Values:	3 <= x <= 33
Default:	3
Requirement:	Mandatory

Specifies the filter's Y size in units of lines.

Notes:

The size entered must be an odd integer between 3 and 33, inclusive.
It must not exceed the database size.
The Y size can be different from the X size (i.e., the filter does not have to be square).
If FilterYSize is not specified, the value for FilterXSize will be used.

DETAILS

FSHARP uses a subtractive smoothing method to sharpen an image. First, an average filter is applied to the image. The averaged image retains all low spatial frequency information but has its high frequency features, such as edges and lines, attenuated. Consequently, the averaged image is subtracted from its original and the resultant difference image will have only the edges and lines substantially remaining. After the edges are determined in this manner, the difference image is added back to the original to give an edge enhanced image. The resultant image will have clearer high frequency detail; however there is a tendency for noise to be enhanced, as might be expected.

The dimensions of the filter window must be odd. The minimum filter size is 1 by 3 (or 3 by 1), and the maximum filter size allowed is 33 by 33. The filter window does not need to be square. For 8-bit layers, if the result is less than 0, it will be truncated to 0; if the result is more than 255, it will be truncated to 255.

A bitmap specifies the area within the input layer which will be processed. Only this area will be filtered and the rest of the image will be unchanged. If no bitmap is connected, the entire database is processed.

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