Is the ground truth mask a binary mask (only 0 or 1)?

[hdjsjyl]

Hi Author,
Thanks for your excellent work. I would like to ask whether the ground truth and prediction are binary masks (only includes 0 or 1)?
If the prediction and ground truth are not 0s or 1s, should we use a threshold value to make it to be a binary mask? If yes, how do we choose the threshold value, is it 128 or 0.5? If yes, why did we choose them as the threshold values? Thank you!