def clip_grid_by_polygons(A, geotransform, polygons):
"""Clip raster grid by polygon.
Args:
* A: MxN array of grid points
* geotransform: 6-tuple used to locate A geographically
(top left x, w-e pixel resolution, rotation,
top left y, rotation, n-s pixel resolution)
* polygons: list of polygon geometry objects or list of polygon arrays
Returns:
points_covered: List of (points, values) - one per input polygon.
Implementing algorithm suggested in
https://github.com/AIFDR/inasafe/issues/91#issuecomment-7025120
.. note:: Grid points are considered to be pixel-registered which means
that each point represents the center of its grid cell.
The required half cell shifts are taken care of by the
function :func:`geotransform_to_axes`.
If multiple polygons overlap, the one first encountered will be used.
"""
# Convert raster grid to Nx2 array of points and an N array of pixel values
ny, nx = A.shape
x, y = geotransform_to_axes(geotransform, nx, ny)
points, values = grid_to_points(A, x, y)
# Generate list of points and values that fall inside each polygon
points_covered = []
remaining_points = points
remaining_values = values
for polygon in polygons:
#print 'Remaining points', len(remaining_points)
if hasattr(polygon, 'outer_ring'):
outer_ring = polygon.outer_ring
inner_rings = polygon.inner_rings
else:
# Assume it is an array
outer_ring = polygon
inner_rings = None
inside, outside = in_and_outside_polygon(remaining_points,
outer_ring,
holes=inner_rings,
closed=True,
check_input=False)
# Add features inside this polygon
points_covered.append((remaining_points[inside],
remaining_values[inside]))
# Select remaining points to clip
remaining_points = remaining_points[outside]
remaining_values = remaining_values[outside]
return points_covered
def get_geometry(self):
"""Return longitudes and latitudes (the axes) for grid.
Note:
Return two vectors (longitudes and latitudes) corresponding to
grid. The values are offset by half a pixel size to correspond to
pixel registration.
I.e. If the grid origin (top left corner) is (105, 10) and the
resolution is 1 degrees in each direction, then the vectors will
take the form
longitudes = [100.5, 101.5, ..., 109.5]
latitudes = [0.5, 1.5, ..., 9.5]
"""
# Get parameters for axes
g = self.get_geotransform()
nx = self.columns
ny = self.rows
# Compute x and y axes
x, y = geotransform_to_axes(g, nx, ny)
# Return them
return x, y
def clip_grid_by_polygons(A, geotransform, polygons):
"""Clip raster grid by polygon.
Args:
* A: MxN array of grid points
* geotransform: 6-tuple used to locate A geographically
(top left x, w-e pixel resolution, rotation,
top left y, rotation, n-s pixel resolution)
* polygons: list of polygon geometry objects or list of polygon arrays
Returns:
points_covered: List of (points, values) - one per input polygon.
Implementing algorithm suggested in
https://github.com/AIFDR/inasafe/issues/91#issuecomment-7025120
.. note:: Grid points are considered to be pixel-registered which means
that each point represents the center of its grid cell.
The required half cell shifts are taken care of by the
function :func:`geotransform_to_axes`.
If multiple polygons overlap, the one first encountered will be used.
"""
# Convert raster grid to Nx2 array of points and an N array of pixel values
ny, nx = A.shape
x, y = geotransform_to_axes(geotransform, nx, ny)
points, values = grid_to_points(A, x, y)
# Generate list of points and values that fall inside each polygon
points_covered = []
remaining_points = points
remaining_values = values
for polygon in polygons:
#print 'Remaining points', len(remaining_points)
if hasattr(polygon, 'outer_ring'):
outer_ring = polygon.outer_ring
inner_rings = polygon.inner_rings
else:
# Assume it is an array
outer_ring = polygon
inner_rings = None
inside, outside = in_and_outside_polygon(remaining_points,
outer_ring,
holes=inner_rings,
closed=True,
check_input=False)
# Add features inside this polygon
points_covered.append(
(remaining_points[inside], remaining_values[inside]))
# Select remaining points to clip
remaining_points = remaining_points[outside]
remaining_values = remaining_values[outside]
return points_covered
def get_geometry(self):
"""Return longitudes and latitudes (the axes) for grid.
Note:
Return two vectors (longitudes and latitudes) corresponding to
grid. The values are offset by half a pixel size to correspond to
pixel registration.
I.e. If the grid origin (top left corner) is (105, 10) and the
resolution is 1 degrees in each direction, then the vectors will
take the form
longitudes = [100.5, 101.5, ..., 109.5]
latitudes = [0.5, 1.5, ..., 9.5]
"""
# Get parameters for axes
g = self.get_geotransform()
nx = self.columns
ny = self.rows
# Compute x and y axes
x, y = geotransform_to_axes(g, nx, ny)
# Return them
return x, y
