How to create a custom convolution filter

static void customConvolutionFilter(IRaster raster)throws Exception{
    //The following code sample sets up a horizontal line detection filter and apply it on a raster
    //create a convolution filter using a custom kernel
    IRasterConvolutionFilter newFilter = new RasterConvolutionFilter();
    double[][] kernel = new double[][]{
        {
             - 1,  - 1,  - 1, 2, 2, 2,  - 1,  - 1,  - 1
        }
    };
    newFilter.putCoefficients(kernel);
    newFilter.setSize(3, 3);

    //apply the filter to the raster
    IPixelOperation pixelOperation = (IPixelOperation)raster;
    pixelOperation.setPixelFilterByRef((IPixelFilter)newFilter);

    //save the result
    ISaveAs saveas = new ISaveAsProxy(raster);
    saveas.saveAs("c:\\temp\\convolution_output.img", null, "IMAGINE Image");
}