def dataset2outlinepolygon(dataset):
""" Return polygon formed by pixel edges. """
nx, ny = dataset.RasterXSize, dataset.RasterYSize
npoints = 2 * (nx + ny) + 1
array = np.empty((npoints, 2))
# Construct pixel indices arrays
px = np.empty(npoints, dtype=np.uint64)
py = np.empty(npoints, dtype=np.uint64)
# top
a, b = 0, nx
px[a:b] = np.arange(nx)
py[a:b] = 0
# right
a, b = nx, nx + ny
px[a:b] = nx
py[a:b] = np.arange(ny)
# bottom
a, b = nx + ny, 2 * nx + ny
px[a:b] = np.arange(nx, 0, -1)
py[a:b] = ny
# left
a, b = 2 * nx + ny, 2 * (nx + ny)
px[a:b] = 0
py[a:b] = np.arange(ny, 0, -1)
# repeat first
px[-1], py[-1] = 0, 0
# Use geotransform to convert the points to coordinates
xul, dxx, dxy, yul, dyx, dyy = dataset.GetGeoTransform()
array[:, 0] = xul + dxx * px + dxy * py
array[:, 1] = yul + dyx * px + dyy * py
return vectors.array2polygon(array)
def dataset2outline(dataset, projection=None):
"""
Return a polygon formed by dataset edges, wrapped in a Geometry.
TODO Make use of np.dot, ideal for geotransform stuff.
"""
nx, ny = dataset.RasterXSize, dataset.RasterYSize
if projection is None:
# will not be transformed, corners are enough
p, a, b, q, c, d = dataset.GetGeoTransform()
points = np.dot([[a, b], [c, d]], [[0, nx, nx, 0, 0],
[0, 0, ny, ny, 0]]) + [[p], [q]]
polygon = vectors.points2polygon(points.transpose())
else:
# take all pixelcrossings along the edge into account
npoints = 2 * (nx + ny) + 1
array = np.empty((npoints, 2))
# Construct pixel indices arrays
px = np.empty(npoints, dtype=np.uint64)
py = np.empty(npoints, dtype=np.uint64)
# top
a, b = 0, nx
px[a:b] = np.arange(nx)
py[a:b] = 0
# right
a, b = nx, nx + ny
px[a:b] = nx
py[a:b] = np.arange(ny)
# bottom
a, b = nx + ny, 2 * nx + ny
px[a:b] = np.arange(nx, 0, -1)
py[a:b] = ny
# left
a, b = 2 * nx + ny, 2 * (nx + ny)
px[a:b] = 0
py[a:b] = np.arange(ny, 0, -1)
# repeat first
px[-1], py[-1] = 0, 0
# Use geotransform to convert the points to coordinates
xul, dxx, dxy, yul, dyx, dyy = dataset.GetGeoTransform()
array[:, 0] = xul + dxx * px + dxy * py
array[:, 1] = yul + dyx * px + dyy * py
polygon = vectors.array2polygon(array)
geometry = vectors.Geometry(polygon)
if projection is None or projection == dataset.GetProjection():
return geometry
geometry.transform(source=dataset.GetProjection(), target=projection)
return geometry
