Angle Measurement

[Fermi.y]

Hello, how could i calculate the angle in the picture attached ? 

[GerdW]

Hi Fermi,

how could i calculate the angle in the picture attached ? 

First use some image processing to find the red lines.

Then find their endpoints and the corner coordinates. Then calc the angle from the coordinates.

Please don't post such questions in the VersionConversion board.

Is the question related to LabVIEW at all?

[jwscs]

this https://en.wikipedia.org/wiki/Hough_transform comes to mind

[Fermi.y]

Hi, i want to measure the angle of contact of a drop of water with surface in real time, i did make a VI to obtain images like the attached one, then i wanna know how could i calculate the angle for different shapes of the drop.

[Fermi.y]

Sorry guys i just make a new thread.

https://forums.ni.com/t5/LabVIEW/Contact-Angle-Measurement/td-p/3771150

[pincpanter]

You have another thread already open for the same subject. Please stick with it.

[jwscs]

seems someone (i guess gerdw) moved your thread here to the correct board.

so you can stick with this one.

[jwscs]

so i asked myself, how can you define the angle of impact in general?

what is the significant feature, which lets you differentiate?

from your images i can not find a significant difference,

and i thought your image with the lines, might be your input, but i guess you drew the lines by hand?

[Fermi.y]

Thanks for your Help  jwscs

So, For how to define the angle of impact in general i hope this will explain more

https://en.wikipedia.org/wiki/Contact_angle

About the significant feature, the image Drop.jpg will help you understand the difference.

and yes the lines were drew by hand

[jwscs]

seems this is still an ongoing research topic

what i gather is, that you have to find the horizontal line of the "water" and the ellipse, from there you need some magic (aka gemoetric math) to get the tangent.

search with (at least) "ellipse" and "occlusion" for research papers.

i don't think that labview offers you a complete solution, though i don't know the vison-package.

also there might be significant image cleanup needed beforehand.

if you find something out, let us (me) know in the thread, seems interesting

good luck

EDIT: also you might find something via "computer vision contact angle"

e.g. http://www.shsu.edu/chm_dlw/Williams-Kuhn-et-al-2010-Galvanotechnik.pdf

it seems there is a free plugin for imageJ

but since you want to do it in labview, i think you have to implement it yourself, or find a way to use an external source (like imageJ) from labview

EDIT2: if you can throw money at the problem (or have access already) https://www.sciencedirect.com/science/article/pii/S0263224114001882