Precisions on vector extractions and mask for further analysis

[O. Foussadier]

Hello ! First thank you for this nice tool !

I have several questions for which I did not find the information yet, or missed it.

- I have to export the velocity vectors to analyse and correlate them relatively to other quantities of my system but I am not sure about the meaning of the positions x and y. Are they corresponding to the "starting" point of the velocity vector , or the middle point of the velocity vector ?

- I would also like to work with the mask I applied for my next analysis but I don't understand what the mask matlab object I exported contains and if there is a not too complicated way to obtain the contour. Could you enlight me on this ?

-Finally, I noticed that the mask was applied on the GUI but when I export, on the divergence for exemple, it is not directly applied. Is it normal ? Or should/could I do something for that ?

Thanks a lot for your help,

Best regards,

Oriane

[William Thielicke (Shrediquette)]

Hi,

- in Matlab/PIVlab, the default is that the velocity  vectors start at the grid point. So x and y correspond to the starting point of the vector.

- If you save your masks from PIVlab, you can open the resulting mat file in Matlab and edit the coordinates if you like. e.g. like tis:

I = imread('baby.jpg');
figure; imshow(I); 

mask_coordinates=cell2mat(masks_in_frame{1,1}(1,2))

h = drawpolygon('Position',mask_coordinates);

- Your third question is discussed here: https://groups.google.com/g/pivlab/c/PNKN1GRDPzw/m/OnyPK1vPAAAJ

[O. Foussadier]

Perfect ! Thank you very much for these precisions, exactly what I needed !