MATLAB - Calculate distance/perimeter of an object in 2D image

[Ping Ong]

Hi, I want to find out how thick/big/fat is the object in the image.

For example, there is a tree in the image(photograph), I want to use MATLAB to calculate how big the tree trunk is.
Problem: Find out the perimeter of trunk as shown in the first picture (named "perimeter.PNG". attached here.

1) Can I use 3D calculation with front view and side view images only(Only use 1 camera)?
2) Or find out the length of trunk from front view ( second image, named "length.PNG") and combine with other algorithm?
3) If the methods I suggested above are not possible, any possible solutions?

p/s: will use matlab, if MATLAB can't do these,any suggestion on software?

Will very appreciate on your suggestions.
Thanks in advance!

 

[SteamKing]

Without some known reference length, I don't see how this can be done. You might as well ask MATLAB to guess your height and weight.

 

[Ping Ong]

Without some known reference length, I don't see how this can be done. You might as well ask MATLAB to guess your height and weight.

How if height is given or another object in the image with known size?? Any solution? Thanks