Hi folks,
I'm trying to find the centroid of a circular object, but I sometimes get negative (!) values for X or Y. I outline it with the polygon tool, under "set measurements" I chose area, centroid, and feret's diameter, and then I select "analyze, measure." Most of the time this works fine. However, if I encompass too large an area, I get negative values for either X or Y of the centroid. My image is a 41 M tiff, 2552 pixels wide by 4200 pixels high. My latest results from "measure" were: area: 1210035 X: 1357.474 Y: -1649.551 diam: 1343.317 Whereas the actual values should be about: X: 1344 Y: 1944 diam: 1308 In this case, maybe the Y value is the only incorrect one, but since there's no way the answer could be negative, it makes me distrust all the values. Is anyone else familiar with this problem, and does anyone have suggestions for getting the right answer? Thanks. -Gwen -- 01000111011101110110010101101110 010000100110000101110010011011100110010101110011 |
Search the release notes for "centroid" and you will find this:
v1.37g, 15 May 2006 Fixed a bug that could cause calculated centroid coordinates to be incorrect with large images. -wayne On Jul 19, 2006, at 3:02 PM, Gwen Barnes wrote: > Hi folks, > > I'm trying to find the centroid of a circular object, but I sometimes > get > negative (!) values for X or Y. > > I outline it with the polygon tool, under "set measurements" I chose > area, > centroid, and feret's diameter, and then I select "analyze, measure." > Most > of the time this works fine. However, if I encompass too large an > area, I > get negative values for either X or Y of the centroid. My image is a > 41 M > tiff, 2552 pixels wide by 4200 pixels high. My latest results from > "measure" were: > > area: 1210035 > X: 1357.474 > Y: -1649.551 > diam: 1343.317 > > Whereas the actual values should be about: > > X: 1344 > Y: 1944 > diam: 1308 > > In this case, maybe the Y value is the only incorrect one, but since > there's > no way the answer could be negative, it makes me distrust all the > values. > > Is anyone else familiar with this problem, and does anyone have > suggestions > for getting the right answer? Thanks. > > -Gwen > > -- > 01000111011101110110010101101110 > 010000100110000101110010011011100110010101110011 > |
Great, thanks!
-Gwen On 7/19/06, Wayne Rasband <[hidden email]> wrote: > > Search the release notes for "centroid" and you will find this: > > v1.37g, 15 May 2006 > Fixed a bug that could cause calculated centroid > coordinates to be incorrect with large images. > > -wayne > > On Jul 19, 2006, at 3:02 PM, Gwen Barnes wrote: > > > Hi folks, > > > > I'm trying to find the centroid of a circular object, but I sometimes > > get > > negative (!) values for X or Y. > > > > I outline it with the polygon tool, under "set measurements" I chose > > area, > > centroid, and feret's diameter, and then I select "analyze, measure." > > Most > > of the time this works fine. However, if I encompass too large an > > area, I > > get negative values for either X or Y of the centroid. My image is a > > 41 M > > tiff, 2552 pixels wide by 4200 pixels high. My latest results from > > "measure" were: > > > > area: 1210035 > > X: 1357.474 > > Y: -1649.551 > > diam: 1343.317 > > > > Whereas the actual values should be about: > > > > X: 1344 > > Y: 1944 > > diam: 1308 > > > > In this case, maybe the Y value is the only incorrect one, but since > > there's > > no way the answer could be negative, it makes me distrust all the > > values. > > > > Is anyone else familiar with this problem, and does anyone have > > suggestions > > for getting the right answer? Thanks. > > > > -Gwen > > > > -- > > 01000111011101110110010101101110 > > 010000100110000101110010011011100110010101110011 > > > |
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