GridFilter2

The GridFilter2 method applies a filter to an existing grid.

The process applies methods of digital image analysis to grids. This includes a broad suite of smoothing (low-pass) filters, as well as contrast enhancement filters, edge enhancement filters, edge detection filters, general high-pass filters, etc. Surfer also includes the capability for user-defined, general linear filters.

Returns a Boolean value. The value is 'True', if the filtering process is successful, otherwise it is 'False'.

Syntax

object.GridFilter2( InGrid, Filter, EdgeOp, BlankOp, NumPasses, EdgeFill, BlankFill, NumRow, NumCol, Param1, Param2, UserFilter, OutGrid, OutFmt, OutGridOptions)

Parameter	Type	Required/ Optional	Default	Description
InGrid	String	Required		This provides the path and file name of the input grid file.
Filter	SrfFilter	Required		This specifies the filter type.
EdgeOp	SrfFilterEdge	Optional		This specifies the edge of grid method.
BlankOp	SrfFilterBlank	Optional		This specifies the NoData nodes method.
NumPasses	Integer	Optional		This specifies the number of passes, i.e., number of times the filter is applied.
EdgeFill	Double	Optional		This specifies the fill value when SrfFilterEdge=srfFltEdgeFill.
BlankFill	Double	Optional		This specifies the fill value when SrfFilterBlank=srfFltBlankFill.
NumRow	Integer	Optional		This is used when filter size can be changed, number of rows, must be odd.
NumCol	Integer	Optional		This is used when filter size can be changed, number of columns, must be odd
Param1	Variant	Optional		See Remarks section.
Param2	Variant	Optional		See Remarks section.
UserFilter	Variant	Optional		This specifies the two dimensional array of doubles, dimensioned to NumRows and NumCol, element 1,1 is the lower left corner, used when SrfFilter=srfFilterUserSpecified.
OutGrid	String	Optional	""	This provides the path and file name of the output grid file.
OutFmt	SrfGridFormat	Optional	srfGridFmtS7	This provides the output grid format.
OutGridOptions	String	Optional	""	This provides the output option string for the grid format.

Remarks

Param1 and Param2 depend upon the SrfFilter setting as follows:

Filter	Param1	Param2
srfFilterDist	Power
srfFilterInvDist	Power	Central Weight
srfFilterGaussianLP	Alpha
srfFilterThresholdAve	Threshold

Example 1

This is an example for how to use GridFilter2.

Dim Filter(1 To 7,1 To 7) As Double

For i=1 To 7

For j=1 To 7

Filter(i,j) = (i-1)*7 + j-1

Next

Next

status = SurferApp.GridFilter2(SurferApp.Path+"\Samples\demogrid.grd", _

SrfFilterUserSpecified,srfFltEdgeBlank,

UserFilter:=Filter)

Example 2

This example demonstrates how to apply a filter to diablo.grd, save the file as Filter.grd and save the spatial references as an Esri AUX.XML file.

Surfer.GridFilter2(InGrid:=InGridPath+"diablo.grd", Filter:=srfFilterAvg, OutGrid:=OutGridPath + "Filter.grd", OutGridOptions:= "UseDefaults=1, ForgetOptions=1, SaveRefInfoAsAUXXML=1")

Example 3

This script displays all the methods in the Application object.

Used by: Application object