How can I measure the temperature of each pixel?

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Mokhtar 2019-3-14

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评论： Mokhtar 2019-3-20

How can I measure the temperature for each pixel from a thermography image. I'm attaching an example of one of the images I took.

Can anyone help me?

Thanks.

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Mokhtar 2019-3-14

编辑：Mokhtar 2019-3-14

I didn't quite understand your point but here is an example of an original picture taken using FLIR thermography camera.

Please let me know if you need more info and thank you so much for the prompt response.

Rik 2019-3-14

Look at the extention of that file: fcf is not a normal image file. The temperature scale you can see in the program is probably encoded in that file. You can attach it as a file (you might need to zip it first).

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Image Analyst 2019-3-18

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Of course it's better to use the actual image if you have one that has actual temperature data in it. But if you don't, like you have the cheapest FLIR one phone camera, then you can extract out the colorbar and use it to convert to temperature. See attached demo.

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Image Analyst 2019-3-19

在 MATLAB Online 中打开

The camera or software you're using will most likely put the color bar in the same location regardless what is happening in your scene. Therefore you can determine the location with any program (or imtool in MATLAB) and use those coordinates to crop out the colorbar.

Then everything to the left of the colorbar will be your image so crop it out

rgbImage = rgbImage(:, 1:leftColumnOfColorBar-1, :);

Mokhtar 2019-3-20

Thank you so much Image Analyst, I managed to crop the image but I think the code couldn't read the colors of the area of interest. As you can see in the original image, there is a contrast between the cloro of the blade and the two areas of interest (kind of brighter). However, the code recognises everything as the same grey degree. This is what I got:

Any idea what is the reason behind this? and is there a way to fix it?

Thanks again.

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Guillaume 2019-3-14

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编辑：Guillaume 2019-3-14

You can't. Your thermography image is not the raw image from the sensor. It's a processed image that associate false colour to the raw signal.

Your software can convert the raw signal into temperature because:

It knows the characteristics of the lens (in particular its absorption)
It knows the exposure of your image
It knows the response of the sensor vs wavelength
probably some more dependencies that I've forgotten

Even if you had the raw image from the sensor, unless you know all of the above, you won't be able to convert to temperature. To get true temperature you also need to know the emissivity of the object you're imaging.

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Mokhtar 2019-3-18

Hi,

I copied the code and changed the intensity values according to the image I am trying to test. I then ran the code but I couldn't find any outcome. It just keep typing the name of the image (test)> I am sorry again for my lack of knowledge in Matlab but can you tell me where can I locate the outcome(The number of pixels that have a specific range of temperature)?

Thanks.

Guillaume 2019-3-18

temperature is the array (the same size as the image) that contains the temperature of each pixel. temperature(1, 1) is the temperature of the upper-left pixel. temperature(end, end) is the temperature of the bottom-right pixel.

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