How can I detect temperature from facial thermal camera

Hi, I am working on a project with facial thermal camera. I need to detect 5 regions of interest in the face: the left and right supraorbital, the left and right periorbital and the nose. I have to track this 5 regions on interest during video record and then extract temperature from this ROIs. I have no skills in Image processing. Does anyone can help me?

Thanks a lot.

Answer 1

[Image Analyst]

You need to have something that identifies the regions, like a binary image or some coordinates. Then you can just do

meanTemperature = mean(thermalImage(binaryImage));

Attached demo may help.

[Mélodie]

Thank you very much for your answer!

I don't really understand why the mean of thermalImage(binaryImage) will give me the temperature (and in what units?) Sorry for my question, I have really no skills in image processing.

[Joseph Cheng]

the units depends on the dynamic range of your data and what the camera is if the data directly in counts, or is the data already in degrees C/F/K already?

What IA described would get you the average (counts or temp) of the masked facial region(s) but you'll have to convert the number if it isn't already in degrees C/F/K. The conversion can be found if using calibrated sources or probably in the camera's spec.

[Image Analyst]

binaryImage is an image the same size as your thermal image. It's true or false at each pixel and says whether to use that pixel or not. When you do thermalImage(binaryImage), it strings together all the pixels values where binaryImage is true - in other words, it gets all the values of the pixels that you told it to. This is a 1D vector. Then mean() simply gets the mean value of all those pixel values. You can get binaryImage either by thresholding, like if you want to find all temperatures above 500 degrees C or something, or you can get it by tracing a region with imfreehand(), or via other ways. In what way do you want to specify your "foreground" pixels?

[Mélodie]

Thank you very much for both of your answer. I think I better understand now. I have to check in the camera's specifications about the data and temperature units. So for the 5 ROIs (as you can see enclosed), I want to do a hand selection by tracing a rectangle using ginput. And after I would like to do a tracking using a cross-search algorithm. I have one code already done but it's for file .txt and I use file .seq so for the moment I didn't succeed to do that.

[Image Analyst]

Check out imrect() or rbbox() for drawing boxes. But if the face is moving around, then you can't have fixed coordinates.

[Mélodie]

Ok thank you but it is not possible to get the temperature from each frame?

[Image Analyst]

Why not? Why can't you?

[Mélodie]

Okay thank you so much for your answers, it helps me a lot.