Mavic Pro Dual thermal images: thermal information from grayscale palette

[sebastianbarria]

Hi everyone.
I'm working with the mavic 2 dual enterprise and it shows the temperature in the screen, but when it stores a thermal image, it doesn´t record the thermal information.
We asked to the DJI support and they answered this:

With regards to your concern about the Mavic 2 Enterprise Dual thermal camera, as of now the M2ED cannot save any RAW/TIFF format photos. So it cannot record the thermal data in the photos. But we have forwarded this information to our R&D department. If there's any updates, possible that it will be added in the future firmware updates.

So, we tried this:
We set up the camera to use a temperature range of -10ºC and 140ºC and we use the grayscale palette. That wat, we're assuming that the -10ºC should be black (0,0,0) in the image and the 140ºC should be white (255,255,255) in the image.

Then, we read the image, pixel by pixel, and we convert the RBG value to the equivalent temperature (in the -10 and 140 degrees range).

But it seems not to work as accurately as it should.
Have anyone tried this before?... should it be possible (logical) to get the temperature information from a b/w image?