An improved adaptive Chord-to-Point distance accumulation algorithm (ACPDA) is proposed which can handle adjacent corners

obtuse corners

and round corners. The main advantages of our implementation include: 1) the neighborhood of the candidate corners is re-detected for avoiding loss of the adjacent corners

which making the localization of corners more precise; 2) an adaptive threshold for each curve is set for removing the false corners

avoiding loss of the obtuse corner; 3) a local adaptive threshold is constructed to remove the round corners effectively. The experimental results have evaluated the performance of the ACPDA.