def apply_polygons()

in fvcore/transforms/transform.py [0:0]

• 21 lines of code
• 10 McCabe index (conditional complexity)

    def apply_polygons(self, polygons: list) -> list:
        """
        Apply crop transform on a list of polygons, each represented by a Nx2 array.
        It will crop the polygon with the box, therefore the number of points in the
        polygon might change.

        Args:
            polygon (list[ndarray]): each is a Nx2 floating point array of
                (x, y) format in absolute coordinates.
        Returns:
            ndarray: cropped polygons.
        """
        import shapely.geometry as geometry

        # Create a window that will be used to crop
        crop_box = geometry.box(
            self.x0, self.y0, self.x0 + self.w, self.y0 + self.h
        ).buffer(0.0)

        cropped_polygons = []

        for polygon in polygons:
            polygon = geometry.Polygon(polygon).buffer(0.0)
            # polygon must be valid to perform intersection.
            if not polygon.is_valid:
                continue
            cropped = polygon.intersection(crop_box)
            if cropped.is_empty:
                continue
            if not isinstance(cropped, geometry.collection.BaseMultipartGeometry):
                cropped = [cropped]
            # one polygon may be cropped to multiple ones
            for poly in cropped:
                # It could produce lower dimensional objects like lines or
                # points, which we want to ignore
                if not isinstance(poly, geometry.Polygon) or not poly.is_valid:
                    continue
                coords = np.asarray(poly.exterior.coords)
                # NOTE This process will produce an extra identical vertex at
                # the end. So we remove it. This is tested by
                # `tests/test_data_transform.py`
                cropped_polygons.append(coords[:-1])
        return [self.apply_coords(p) for p in cropped_polygons]