How to create a custom convolution filter

public static void CustomConvolutionFilter(IRaster raster)
{
    //The following code sample sets up a horizontal line detection filter and applies it to a raster
    //to create a convolution filter using a custom kernel.
    IRasterConvolutionFilter newFilter = new RasterConvolutionFilterClass();
    newFilter.SetSize(3, 3);
    double[] kernel = new double[9]
    {
         - 1,  - 1,  - 1, 2, 2, 2,  - 1,  - 1,  - 1
    };
    newFilter.PutCoefficients(ref kernel);

    //Apply the filter to the raster.
    IPixelOperation pixelOperation = (IPixelOperation)raster;
    pixelOperation.PixelFilter = (IPixelFilter)newFilter;

    //Save the result.
    ISaveAs saveas = (ISaveAs)raster;
    saveas.SaveAs(@"c:\temp\convolution_output.img", null, "IMAGINE Image");
}

Public Shared Sub CustomConvolutionFilter(ByVal raster As IRaster)
'The following code sample sets up a horizontal line detection filter and applies it to a raster
'to create a convolution filter using a custom kernel.

'Define the kernal
Dim NewFilter As IRasterConvolutionFilter = New RasterConvolutionFilterClass()
NewFilter.SetSize(3, 3);
Dim kernel() As Double = New Double(9) {-1, -1, -1, 2, 2, 2, -1, -1, -1}
NewFilter.PutCoefficients( kernel)

'Apply the filter to the raster.
Dim pixelOperation As IPixelOperation = CType(raster, IPixelOperation)
pixelOperation.PixelFilter = CType(NewFilter, IPixelFilter)

'Save the result.
Dim saveas As ISaveAs = CType(raster, ISaveAs)
saveas.SaveAs("c:\temp\convolution_output.img", Nothing, "IMAGINE Image")
End Sub