Angle measurement from colour survey

vector-field
orientationj
Tags: #<Tag:0x00007fd542275230> #<Tag:0x00007fd5422750a0>

#1

Hi All,
I am new in the forum but I’ve been using imageJ for a while.
However, I’d like to do something and I am not sure how.

I created a vector field image like the one attached

I’d like to get angle measurement corresponding to these vector

Is it possible?
Or I have done a color survey like the one attached color surveys.
in which each color correspond to a specific angle. can I somehow output these numbers?
Can I actually output measurements for angles within the colour survey?
I know it’s possible for a region of interest but what if for each color in the image?

Hope it makes sense.
Thanks


#2

Good day Laura!

I created a vector field image like the one attached

If you’ve created the vector field you should already know the values – no?

Regards

Herbie


#3

Hi,
thanks for your reply.
I’ve created the vectors with orientation J plugin which does not give me the values - or if possible I don’t know how to do it. It outputs the vectors only - or the colour survey - without values.

Thanks


#4

@Laura.biology

The developer of that plugin, @daniel.sage, might be able to help you in this case… But have you looked at their OrientationJ plugin page? I have not used this tool myself - but for sure it seems there are ways to access the data you need (maybe the Distribution of Orientations tool…).

eta :slight_smile:


#5

Laura,

did you try “Show Table”?

Extracting local orientation from a vector field that results from local orientation analyses doesn’t make sense for me …

Regards

Herbie


#6

Thank you Eta,
I have actually looked at their website but I could not find anything that explain how to do this - unless I missed it. I suppose there is a way


#7

I tried already but all this numbers do not make any sense to me…
Thanks for suggestions


#8

@Laura.biology

Have you downloaded and tried the Orientation Distribution guy? I think from the histogram that is generated… you can access a ‘List’ of values. Try it out - play a bit - let us know how it goes … and let’s see if @daniel.sage is able to respond in the meantime.

eta :slight_smile:


#9

@etarena

Thank you. I’ll try :slight_smile: and see how it goes


#10

Laura,

use the dx and dy values to calculate the angle via the arcus tangens function.

HTH

Herbie


#11

@Herbie

thank you, that’s helpful.
I’ve got a question, apologies if it sounds silly.
How do I get the arcus tangens function? Never heard of it.

Laura


#12

Laura,

do you remember Pythagoras and his theorem for right-angled triangles?
https://en.wikipedia.org/wiki/Pythagorean_trigonometric_identity

There you find the relation between the angle and both of the short side lengths. Look for the section “Related identities”.

The arcus tangens is the inverse function of the tangens function and results in the angle, given the fraction of the short side lengths.

Regards

Herbie


#13

@Herbie

yeah, I remember now. I know it sounds an excuse but I never done this in English (I am Italian) and it did not come to my mind straight away.

Sorry, last thing, what are DX and DY? what do these numbers represent?

Thanks


#14

Laura,

the arcus tangens is the same in Italian!

What could dx and dy be in the relation between the short side lengths and the angle?
Of course, they are the short side lengths.

Regards

Herbie


#15

ok, thanks for help!
sorry for bothering, then!


#16

I used OrrientationJ to get the average angle of ridges in an image and got a good comparison with a manual angle measure.


#17

That’s helpful, thank you @rondespain


#18

Ron DeSpain,

as it is made clear in the original post, the local/regional orientations of an image are of interest and I’ve shown how this information can be gained from the table that is produced by “OrientationJ Vector Field”. If this doesn’t work for the original poster or if the task has changed, then this would be more than interesting to know.

Regards

Herbie


#19

Hi Herbie
what are the units of the orientation column from "OrientationJ Vector Field”?


#20

Good day Ron DeSpain,

the units don’t matter, because of

phi = arctan( dy / dx )

Regards

Herbie