Can I manually move the position of an automatically computed centroid?
Hi,
I am calculating area/radius/diameter measurements of larval fish otoliths which are basically spherical...so I am using the automatic polygon trace to get the outline and selected measurements. The centroid is obviously calculated automatically, but doesn't always match the otolith core exactly - is there any way to manually move this point to where I want it to be, then run the automatic calculations again? It really just affects the radius measurements.
Or is it better to just do manual line measurements?
Thanks!
Fiona
I am calculating area/radius/diameter measurements of larval fish otoliths which are basically spherical...so I am using the automatic polygon trace to get the outline and selected measurements. The centroid is obviously calculated automatically, but doesn't always match the otolith core exactly - is there any way to manually move this point to where I want it to be, then run the automatic calculations again? It really just affects the radius measurements.
Or is it better to just do manual line measurements?
Thanks!
Fiona
0
Best Answer
-
Fiona,
If you actually want to make Radius measurement to use different center, moving the object will not change anything, as radius is always measured from automatically calculated center.
There is another way of calculating Radius data using "Incremental distance" tool.
Use the following steps when you already have outlines of your main object:
1. Draw a small circle at the position of the center (where you need it), the circle can be as small as 1 pixel diameter.
2. Select fist the small circle and then using Ctrl-Click the main outline (the selection order is important!).
3. Click "Incremental Distance" button on the Measure tab.
The tool will generate radius measurements from the central circle to the outline points with given interval.
I've attached the example.
Best regards,
Yuri
0
Answers
If you are using Count operation to segment objects, then the object outlines by default are locked and cannot be moved. You can unlock them using the "Unlock objects" menu item in the Hide/Show button drop-down in Select ribbon bar of Count/Size tab. After unlocking you can move the whole object and correspondingly the centroid.
Is that what you want?
If you are doing Otolith analysis, then you may check our free App, which is specifically designed for that purpose. You can download it from here:
http://www.mediacy.com/index.aspx?page=ViewSolution&solid=1725
Regards,
Yuri
I'm dealing with single objects, so I don't need to segment anything. Here's an image (hope it's not too big!) of the radius measurements I'm collecting. You can see they all start in the core region - which is not always the calculated centroid. I was hoping to automate the procedure using the polygon tool rather than manually drawing lines for each image...as I also need area/diameter etc.
Regards
Fiona