Add algorithm class ConvexHullIncremental

algorithm.py

@@ -191,3 +191,111 @@ class NearestNeighborsSweep(Algorithm):
                     self._result["points"][0], self._result["points"][1] \
                 ).draw(canvas, width, height, max_x, max_y, "#FF0000")
 
+class ConvexHull(Algorithm):
+
+    """This algorithm calculates the convex hull for a set of points"""
+
+    def __init__(self, point_set=None):
+        super().__init__()
+        if isinstance(point_set, list):
+            for pnt in point_set:
+                if not isinstance(pnt, point.Point):
+                    raise Exception(self, "Inputs have to be of type point.Point!")
+            self._input = copy.deepcopy(point_set)
+            self._ready = True
+        elif point_set is not None:
+            raise Exception(self, "Wrong input type for point_set")
+        self._sss = {}  # The sweep state structure
+        self._es = []   # The event queue
+        self._result = {"success": False, \
+                        "lt": [], \
+                        "lb": [], \
+                        "rt": [], \
+                        "rb": [], \
+                        "hull": []}
+    def start(self):
+        """Start the performing the algorithm. Return True if it was successful"""
+        if not super().start():
+            return False
+
+        self._result["success"] = False
+        self._sss = {"max": None, \
+                     "min": None}
+        # Populate event structure
+        self._es = copy.deepcopy(self._input)
+        # Sort the input elements
+        self._num_steps["sort"] = point.sort_set(self._es)
+        self._section = "sweep-left-to-right"
+        return True
+    def step(self):
+        """Perform a single step of the algorithm."""
+        if not self._running:
+            return
+
+        if self._section == "sweep-left-to-right":
+            event = self._es.pop(0)
+            if self._sss["min"] is None or self._sss["max"] is None:
+                self._sss["min"] = event
+                self._sss["max"] = event
+            elif event.get_y() < self._sss["min"].get_y():
+                self._result["rb"].append(linesegment.LineSegment(self._sss["min"], event))
+                self._sss["min"] = event
+            elif event.get_y() > self._sss["max"].get_y():
+                self._result["rt"].append(linesegment.LineSegment(self._sss["max"], event))
+                self._sss["max"] = event
+
+            super().step()
+            if len(self._es) == 0:
+                self._sss["min"] = None
+                self._sss["max"] = None
+                self._es = copy.deepcopy(self._input).reverse()
+                self._section = "sweep-right-to-left"
+
+        elif self._section == "sweep-right-to-left":
+            event = self._es.pop(0)
+            if self._sss["min"] is None or self._sss["max"] is None:
+                self._sss["min"] = event
+                self._sss["max"] = event
+            elif event.get_y() < self._sss["min"].get_y():
+                self._result["rb"].append(linesegment.LineSegment(self._sss["min"], event))
+                self._sss["min"] = event
+            elif event.get_y() > self._sss["max"].get_y():
+                self._result["rt"].append(linesegment.LineSegment(self._sss["max"], event))
+                self._sss["max"] = event
+
+            super().step()
+            if len(self._es) == 0:
+                self._section = "sweep-left-to-top"
+
+        elif self._section == "sweep-left-to-top":
+            event = self._es.pop(0)
+            if len(self._es) == 0:
+                self._section = "sweep-left-to-bottom"
+
+        elif self._section == "sweep-left-to-bottom":
+            event = self._es.pop(0)
+            if len(self._es) == 0:
+                self._section = "sweep-right-to-top"
+
+        elif self._section == "sweep-right-to-top":
+            event = self._es.pop(0)
+            if len(self._es) == 0:
+                self._section = "sweep-right-to-bottom"
+
+        elif self._section == "sweep-right-to-bottom":
+            event = self._es.pop(0)
+            if len(self._es) == 0:
+                self._section = "report-hull"
+        elif self._section == "report-hull":
+            for line in self._result["lb"]:
+                self._result["hull"].append(line)
+            for line in self._result["rb"].reverse():
+                self._result["hull"].append(line)
+            for line in self._result["rt"]:
+                self._result["hull"].append(line)
+            for line in self._result["lt"].reverse():
+                self._result["hull"].append(line)
+            self._result["success"] = True
+            self._running = False
+
+