Question: Processing a picture from Rasperry Pi NoIR camera with blue filter and getting NDVI values.

Hi everyone, I would like to know how to get the NDVI image from a picture taken by the Rasperry Pi NoIR camera with a blue filter. I tried using Infragram.

I used a picture from the Rasperry Pi website.

The picture:

I uploaded it on Infragram, clicked on presets, NDVI for blue filters and then colorized. I left the default options that were: Grey, (R-B)/(R+B) and Default Colormap. This is the result:

Now, what is the scale of this image and how can I get it? Just so I explain myself, for scale I mean something such the one in this image (found on this website):

And also, is there a way to get the number of the NDVI value for each pixel of the picture?

Thanks in advance.