I need to detect temperature from thermal image without converting it into gray scale

I have code which convert a thermal image into gray scale image and then the temperature can be detected ...but I am looking for a code that can directly detect temperature from thermal image without it to Gray scale image

Answer 1

[Walter Roberson]

This has been discussed a few times in the past.

The most difficult part of this is in converting the color into a temperature. Thermal images that are in color are always "false color", and most of the time, there is no linear component -- for example converting to L*ab and examining the Chroma turns out to not be linear, and converting to HSV and examining the Hue turns out to not be linear, and so on.

A lot of the time, companies do not publish the key or the color table. One of the major thermal imaging manufacturers historically did not even put a colorbar on the images.

So... you have to go through a calibration phase to figure out what temperature shows up as what color. Unless, that is, there is a color bar, in which case you have to spend time doing image analysis of the color bar in order to build a look-up table relating color and temperature.

There are some manufacturers that are very conscientious about using colors that can be analyzed and converted directly to temperature. Some manufacturers of thermal imaging products produce both a pseudo-color image and a floating point array, stored in the same TIFF file, so that the color data can be read out directly.

But there are a lot of other manufacturers that care more about mass sales to consumers who do not need to do scientific processing of the resulting images.

[Richa Parihar]

Thank you sir for your information and quick repy but the thermal image that I have is having color bar of temperature so now could you suggest me some codes related method.

[Walter Roberson]

Is the colorbar consistent from image to image? Some manufacturers automatically scale for relative temperatures. Or have pre-set ranges, consistent if you are using the same pre-set but different for other pre-sets.

If the colorbar is consistent from image to image, the easiest approach is often to display a sample image in MATLAB, and use datatips to move over the colorbar and read out RGB components and look at the tick labels to see what the related temperature is. You would build the table once, and afterwards your analysis programs could use look-ups to figure out what the temperatures were.

If the colorbar is not consistent range from image to image, then you need to build logic that figures out where the colorbar is on the image and pull out the color scale, and use OCR techniques on the colorbar labels, to build up the map for that particular image.

[Walter Roberson]

That person posted their code, so it is not clear what more you need to proceed ?

[Walter Roberson]

They did post; https://gumroad.com/l/JRVPk . The price they ask looks quite reasonable to me for 200 kilobytes of code. It would cost me at least that much worth of ice-cream or chocolate to write code myself.

... You would have used their code if it had been free, which tells us that you are not primarily concerned about commercial licensing or academic integrity.

[Richa Parihar]

Thank you sir for your reply ...but actually i want to write code by my own with some external help as MATLAB is quite new field to me , and do not know much of GUI and handles and sir I am very much concern about commercial licensing or academic integrity.

[Walter Roberson]

See https://www.mathworks.com/products/matlab/app-designer.html for a tool to help design GUI.

After that what you need to read about is ginput().

Or set up a ButtonDownFcn callback https://www.mathworks.com/help/matlab/ref/matlab.ui.figureappd-properties.html#bu4i700-1-ButtonDownFcn https://www.mathworks.com/help/matlab/ref/matlab.ui.figureappd-properties.html#bu4i700-1-CurrentPoint uifigure() CurrentPoint property

Or see https://www.mathworks.com/matlabcentral/answers/406342-app-designer-how-to-get-mouse-position-when-i-click-on-figure#answer_407550

[Richa Parihar]

Thank you sir