Image segmentation Task: Coloring back label issue

I have this issue (described here: https://stackoverflow.com/questions/52037008/loading-wrong-segmentation-ground-truth-when-training-with-custom-dataset-deephttps://stackoverflow.com/questions/52037008/loading-wrong-segmentation-ground-truth-when-training-with-custom-dataset-deep ) I can’t find out why got bolded black corners. I tried to change the position of the void label, If anyone could give me a tip it would be great.