Hello Komang,
I understand you want to find the spark plasma area, but the plasma area is brighter which is causing issues in analysing the image. You want to distinct between plasma pixels with high intensity and the background with low intensity values.
Thresholding is useful in this case because it can separate the brighter spark plasma area from the darker surrounding area. By setting a threshold value, all pixels with intensities above the threshold are set to white, while all pixels with intensities below the threshold are set to black. This creates a binary image where the spark plasma area is white and the surrounding area is black, making it easier to calculate the area of the spark plasma.
To know about thresholding algorithms in MATLAB, you can refer to this page: https://in.mathworks.com/discovery/image-thresholding.html
I hope this helps!
