--- In [email protected], "mockey_a" <[EMAIL PROTECTED]> wrote:
> But I found the mistake. The mouse is exactly over 1 pixel. Now Sean 
> defines the region that's going to be enlarged:
> xmouse-nRect/nZoom,ymouse-nRect/nZoom,;;+
> nRect/nZoom*2,nRect/nZoom*2
> that's 10 pixel up and left and then 20 pixels down and right, which 
> gives you a 20x20 pixel section.

I don't quite understand it. Would it mean, then, 0 pixel up and 2*0
pixel down is 0 pixel? 1 pixel up and 2 pixel down is 2 pixel, not 3
pixel?

Anyway, adding 1 pixel really improves the behavior. So, possibly my
conception of pixel is wrong, I tend to think pixel as a mathematical
point which I always felt may not be quite correct.

> I think it might be better to define a pixel-radius and a zoom-
> factor for the script to avoid rounding mistakes, like a radius of 
> 10 and a zoom factor of 5, which would give you a section of 21x21 
> and an enlarged picture of 105x105.

There were two choices from the start:
1) based on the big rectangle: intuitive as this one is what we see
2) based on the small rectangle: precise as no division involved

I took the seemingly intuitive approach as this is simpler to imagine
and it's quite straightforward to convert this to the small-rect base.

OK, I'll upload a new one which is somewhat mixed approach: e.g.,

nZoom = 5
nRect = 100/2/nZoom

So, roughly specify the big rectangular dimension, which can be
smaller maximally by 2*nZoom - 1:
specify 100, will get 100
specify 109, will get 100
specify 110, will get 110

Sean






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