MATLAB: Threshold value question using otsu method

Question

I am doing Plant leaf disease detection & classification project. In that i am using otsu method to calculate threshold value for all leaves. But thershold value for some type of leaves could not detect the diseased part correctly..so i am using some constant threshold value(0.17,0.6). Can anyone please give some other method to find threshold value other than otsu method that is suitable for all type of leaves..

Answer 1

See my attached code. I use an image with black background and even black spots inside it. I correctly identify the diseased areas and give the area fraction of them relative to the entire leaf area (diseased + healthy areas).

If this solves your question, please mark as Accepted.