Tutorial example: 2-D array pixel position

In the tutorial "3.1 Handling a 2-D array of data: using an 
Integer2DSet", why are the colored squres (pixels) in the 2D
plot in tutorial.s3.P3_01 not alined with the grid? I mean,
for example the box whose index is (row=2, col=3) neither
have its center nor have its corner at coordinate point (2,3).
I see that if using Continuous 2-D domain values the boxes
are alined as I expected, but why not integer2Dset ?

by the way, I am using Java SDK1.3.1 on Windows2000 and when I
press on the middle mouse button on the plot, the cross and
coordinate numbers show but they never change no matter where
I drag the mouse or click the middle buton.
Any idea as how I get this problem fixed?

Maohai Huang

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