I am trying to segment a batch of images from optical microscope. Attached is one sample image. My goal is to separate four phases in the image and analyze the corresponding volume fraction. I used machine learning approaches implemented in trainable weka segmentation in ImageJ and ilastik, and can roughly segment phases 1, 2 and 3. However, the fourth phase pointed by black arrows, a thin white layer surrounding brown particles, cannot be properly separated from phase 2 or 3. Please let me know if you have any suggestions. Your help will be greatly appreciated.