>I was expecting something like "0 0 0 1 1 1 1 2 2 2",
>and the result was "0 0 0 0 0 1 1 1 2 2" !
>
>The result is not symmetrical !
>
>Can You give me some explanation ?
This looks to me like a classic error of open/closed intervals:
Pictorially, you felt you started with:
+-----+-----+
| | |
| 0 | 2 |
| | |
+-----+-----+
That is, you thought of your images as two rectangles (each only one pixel
on a side), entirely covered with a single value (0 or 2).
Streching this, you expected:
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| | | | | | | | | | |
| 0 | 0 | 0 | 1 | 1 | 1 | 1 | 2 | 2 | 2 |
| | | | | | | | | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
However, I suspect that the code treated the source as:
+-----+-
| |
|0 |2
| |
+-----+-
That is, as values on a half open interval, where 0 was at the left edge,
and the right edge, just beyond the one pixel enclosed, was 2.
With this interpretation of the source, I would expect your code to expand
this to:
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-
| | | | | | | | | |
|0 |0 |0 |0 |0 |1 |1 |1 |1 |2
| | | | | | | | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-
[The right-most 0 could just as easily be a 1... in fact, one might very
well want it randomly picked, with the error propigated over the full
image...]
But, alas, you saw:
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-
| | | | | | | | | |
|0 |0 |0 |0 |0 |1 |1 |1 |2 |2
| | | | | | | | | |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-
My guess is that this result is a combination of both the 'edge',
half-open, style of interpretation, coupled with some slightly incorrect
edge condition code in Java2D. Looks like the filter code does pixels 0
through n - 2 via the filter, then copies pixel n - 1 to the edge. Then
this is either happening twice, or the edge conditions are being pushed
through the filter incorrectly. Either way, there is no way the resulting
values are correct.
- Mark
-------------------
Mark Lentczner
President
Glyphic Technology
444 Castro Street, Suite 811
Mtn. View, CA 94041
[EMAIL PROTECTED]
http://www.glyphic.com/
650/964-5311 voice
650/967-4379 fax
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