A hybrid active contour model based on pre-fitting energy and adaptive functions for fast image segmentation

•An adaptive edge indicator function is proposed to make evolution process more stable and robust to initial contours.•An adaptive sign function is proposed to enable the evolution curve to adjust evolution direction and speed.•New pre-fitting functions are computed before the iteration without online update to reduce computation cost.•A single-well potential function is provided to prevent segmentation failure and increase segmentation speed.