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Intersection of ROIs
| Intersection of ROIs [message #54515] |
Tue, 19 June 2007 01:14 |
Gaurav
Messages: 50
Registered: January 2007
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Member |
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Dear all,
In my previous post I simply presented my current problem about the
inability to convert from data coordinates to device coordinates while
working with Object Graphics. Here I'll outline why I need to do that.
Maybe that will elicit better responses.
What I have is a small ROI (say test_ROI) in data space (a region
defined by the lat/lon values of the polygon vertices). Also, I have a
set of other ROIs- many of which overlap the test_ROI. Now, I need to
know which ROIs have points common with my test_ROI (in other words
overlapping ROIs).
In the case of Direct graphics it was fairly easy. I found the pixels
that came in the test_ROI by using the POLYFILLV routine after I had
converted the vertices of the test_ROI into device space. Thereafter I
took each of these point, converted it from device to Data space and
tested for its presence within each of the multiple ROIs. It may be a
brute force approach but I could not think of any other way.
Can any one suggest me a better way of finding the intersecting
polygons or ROIs. It would be great if one could come up with UNION
and INTERSECTION like functions-especially while working with ROIs and
Shapefiles.
Help, please!
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