Creating and Enriching Graphical User Interfaces - Beginning Java 7 - page 681

The first filter() method call is passed an existing BufferedImage instance
named bi asitsfirstargument.Itssecondargumentis null ,whichtells filter() to
createanew BufferedImage instanceasthedestination.Youcannotpassthesame
BufferedImage instance as the second argument because ConvolveOp doesn't
support in-place filtering for buffered images.
The second filter() method call is passed the buffered image's raster (obtained
byinvoking BufferedImage 's WritableRaster getRaster() method)asits
first argument. It is also passed null as its second argument because ConvolveOp
doesn't support in-place filtering for rasters.
Note Forconvenience,Ifocusonbufferedimage-basedprocessing.Also,Idemon-
stratevariousfilters/imageoperatorsinthecontextofa BIP applicationthat'sincluded
with this topic's code.
You can create a blur kernel that blurs an image by combining equal amounts of
source and neighbor pixel component values. The resulting kernel appears here:
float ninth = 1.0f/9.0f;
float[] blurKernel =
{
ninth, ninth, ninth,
ninth, ninth, ninth,
ninth, ninth, ninth
};
Kernel kernel = new Kernel(3, 3, blurKernel);
Figure 7-29 shows the blur kernel's results—compare with Figure 7-10 .