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# Licensed under a 3-clause BSD style license - see LICENSE.rst
import abc
from collections import OrderedDict
import numpy as np
class Region(metaclass=abc.ABCMeta):
"""
Base class for regions.
Parameters
----------
rid : int or str
region ID
coordinate_frame : `~gwcs.coordinate_frames.CoordinateFrame`
Coordinate frame in which the region is defined.
"""
def __init__(self, rid, coordinate_frame):
self._coordinate_system = coordinate_frame
self._rid = rid
@abc.abstractmethod
def __contains__(self, x, y):
"""
Determines if a pixel is within a region.
Parameters
----------
x, y : float
x , y values of a pixel
Returns
-------
True or False
Subclasses must define this method.
"""
def scan(self, mask):
"""
Sets mask values to region id for all pixels within the region.
Subclasses must define this method.
Parameters
----------
mask : ndarray
An array with the shape of the mask to be uised in `~gwcs.selector.RegionsSelector`.
Returns
-------
mask : ndarray
An array where the value of the elements is the region ID.
Pixels which are not included in any region are marked with 0 or "".
"""
class Polygon(Region):
"""
Represents a 2D polygon region with multiple vertices.
Parameters
----------
rid : str
polygon id
vertices : list of (x,y) tuples or lists
The list is ordered in such a way that when traversed in a
counterclockwise direction, the enclosed area is the polygon.
The last vertex must coincide with the first vertex, minimum
4 vertices are needed to define a triangle
coord_frame : str or `~gwcs.coordinate_frames.CoordinateFrame`
Coordinate frame in which the polygon is defined.
"""
def __init__(self, rid, vertices, coord_frame="detector"):
assert len(vertices) >= 4, ("Expected vertices to be "
"a list of minimum 4 tuples (x,y)")
super(Polygon, self).__init__(rid, coord_frame)
self._vertices = np.asarray(vertices)
self._bbox = self._get_bounding_box()
self._scan_line_range = list(range(self._bbox[1], self._bbox[3] + self._bbox[1] + 1))
# constructs a Global Edge Table (GET) in bbox coordinates
self._GET = self._construct_ordered_GET()
def _get_bounding_box(self):
x = self._vertices[:, 0].min()
y = self._vertices[:, 1].min()
w = self._vertices[:, 0].max() - x
h = self._vertices[:, 1].max() - y
return (x, y, w, h)
def _construct_ordered_GET(self):
"""
Construct a Global Edge Table (GET)
The GET is an OrderedDict. Keys are scan line numbers,
ordered from bbox.ymin to bbox.ymax, where bbox is the
bounding box of the polygon.
Values are lists of edges for which edge.ymin==scan_line_number.
Returns
-------
GET: OrderedDict
{scan_line: [edge1, edge2]}
"""
# edges is a list of Edge objects which define a polygon
# with these vertices
edges = self.get_edges()
GET = OrderedDict.fromkeys(self._scan_line_range)
ymin = np.asarray([e._ymin for e in edges])
for i in self._scan_line_range:
ymin_ind = (ymin == i).nonzero()[0]
if ymin_ind.any():
GET[i] = [edges[ymin_ind[0]]]
for j in ymin_ind[1:]:
GET[i].append(edges[j])
return GET
def get_edges(self):
"""
Create a list of Edge objects from vertices
"""
return [Edge(name='E{}'.format(i - 1), start=self._vertices[i - 1], stop=self._vertices[i])
for i in range(1, len(self._vertices))
]
def scan(self, data):
"""
This is the main function which scans the polygon and creates the mask
Parameters
----------
data : array
the mask array
it has all zeros initially, elements within a region are set to
the region's ID
Algorithm:
- Set the Global Edge Table (GET)
- Set y to be the smallest y coordinate that has an entry in GET
- Initialize the Active Edge Table (AET) to be empty
- For each scan line:
1. Add edges from GET to AET for which ymin==y
2. Remove edges from AET fro which ymax==y
3. Compute the intersection of the current scan line with all edges in the AET
4. Sort on X of intersection point
5. Set elements between pairs of X in the AET to the Edge's ID
"""
# TODO: 1.This algorithm does not mark pixels in the top row and left most column.
# Pad the initial pixel description on top and left with 1 px to prevent this.
# 2. Currently it uses intersection of the scan line with edges. If this is
# too slow it should use the 1/m increment (replace 3 above) (or the increment
# should be removed from the GET entry).
y = np.min(list(self._GET.keys()))
AET = []
scline = self._scan_line_range[-1]
while y <= scline:
AET = self.update_AET(y, AET)
scan_line = Edge('scan_line', start=[self._bbox[0], y],
stop=[self._bbox[0] + self._bbox[2], y])
x = [np.ceil(e.compute_AET_entry(scan_line)[1]) for e in AET if e is not None]
xnew = np.asarray(np.sort(x), dtype=np.int)
for i, j in zip(xnew[::2], xnew[1::2]):
data[y][i:j + 1] = self._rid
y = y + 1
return data
def update_AET(self, y, AET):
"""
Update the Active Edge Table (AET)
Add edges from GET to AET for which ymin of the edge is
equal to the y of the scan line.
Remove edges from AET for which ymax of the edge is
equal to y of the scan line.
"""
edge_cont = self._GET[y]
if edge_cont is not None:
for edge in edge_cont:
if edge._start[1] != edge._stop[1] and edge._ymin == y:
AET.append(edge)
for edge in AET[::-1]:
if edge is not None:
if edge._ymax == y:
AET.remove(edge)
return AET
def __contains__(self, px):
"""even-odd algorithm or smth else better sould be used"""
return px[0] >= self._bbox[0] and px[0] <= self._bbox[0] + self._bbox[2] and \
px[1] >= self._bbox[1] and px[1] <= self._bbox[1] + self._bbox[3]
class Edge:
"""
Edge representation.
An edge has a "start" and "stop" (x,y) vertices and an entry in the
GET table of a polygon. The GET entry is a list of these values:
[ymax, x_at_ymin, delta_x/delta_y]
"""
def __init__(self, name=None, start=None, stop=None, next=None):
self._start = None
if start is not None:
self._start = np.asarray(start)
self._name = name
self._stop = stop
if stop is not None:
self._stop = np.asarray(stop)
self._next = next
if self._stop is not None and self._start is not None:
if self._start[1] < self._stop[1]:
self._ymin = self._start[1]
self._yminx = self._start[0]
else:
self._ymin = self._stop[1]
self._yminx = self._stop[0]
self._ymax = max(self._start[1], self._stop[1])
self._xmin = min(self._start[0], self._stop[0])
self._xmax = max(self._start[0], self._stop[1])
else:
self._ymin = None
self._yminx = None
self._ymax = None
self._xmin = None
self._xmax = None
self.GET_entry = self.compute_GET_entry()
@property
def ymin(self):
return self._ymin
@property
def start(self):
return self._start
@property
def stop(self):
return self._stop
@property
def ymax(self):
return self._ymax
def compute_GET_entry(self):
"""
Compute the entry in the Global Edge Table
[ymax, x@ymin, 1/m]
"""
if self._start is None:
entry = None
else:
earr = np.asarray([self._start, self._stop])
if np.diff(earr[:, 1]).item() == 0:
return None
else:
entry = [self._ymax, self._yminx,
(np.diff(earr[:, 0]) / np.diff(earr[:, 1])).item(), None]
return entry
def compute_AET_entry(self, edge):
"""
Compute the entry for an edge in the current Active Edge Table
[ymax, x_intersect, 1/m]
note: currently 1/m is not used
"""
x = self.intersection(edge)[0]
return [self._ymax, x, self.GET_entry[2]]
def __repr__(self):
fmt = ""
if self._name is not None:
fmt += self._name
next = self.next
while next is not None:
fmt += "-->"
fmt += next._name
next = next.next
return fmt
@property
def next(self):
return self._next
@next.setter
def next(self, edge):
if self._name is None:
self._name = edge._name
self._stop = edge._stop
self._start = edge._start
self._next = edge.next
else:
self._next = edge
def intersection(self, edge):
u = self._stop - self._start
v = edge._stop - edge._start
w = self._start - edge._start
D = np.cross(u, v)
return np.cross(v, w) / D * u + self._start
def is_parallel(self, edge):
u = self._stop - self._start
v = edge._stop - edge._start
if np.cross(u, v):
return False
else:
return True
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