def tiles(self):
"""
Generator that yields an algebra-ready data dictionary for each tile in
the aggregator's tile range.
"""
# Check if any tiles have been matched
if not self.tilerange:
return
algebra_parser = RasterAlgebraParser()
for tilex in range(self.tilerange[0], self.tilerange[2] + 1):
for tiley in range(self.tilerange[1], self.tilerange[3] + 1):
# Prepare a data dictionary with named tiles for algebra evaluation
data = {}
for name, layerid in self.layer_dict.items():
tile = get_raster_tile(layerid, self.zoom, tilex, tiley)
if tile:
data[name] = tile
else:
break
# Ignore this tile if it is missing in any of the input layers
if len(data) < len(self.layer_dict):
continue
# Compute raster algebra
result = algebra_parser.evaluate_raster_algebra(
data, self.formula)
# Convert band data to masked array
result_data = numpy.ma.masked_values(
result.bands[0].data(),
result.bands[0].nodata_value,
)
# Apply rasterized geometry as mask if clip geometry was provided
if self.geom:
result_data = self.mask_by_geom(result, result_data)
yield result_data.compressed()
def tiles(self):
"""
Generator that yields an algebra-ready data dictionary for each tile in
the aggregator's tile range.
"""
# Check if any tiles have been matched
if not self.tilerange:
return
algebra_parser = RasterAlgebraParser()
for tilex in range(self.tilerange[0], self.tilerange[2] + 1):
for tiley in range(self.tilerange[1], self.tilerange[3] + 1):
# Prepare a data dictionary with named tiles for algebra evaluation
data = {}
for name, layerid in self.layer_dict.items():
tile = get_raster_tile(layerid, self.zoom, tilex, tiley)
if tile:
data[name] = tile
else:
break
# Ignore this tile if it is missing in any of the input layers
if len(data) < len(self.layer_dict):
continue
# Compute raster algebra
result = algebra_parser.evaluate_raster_algebra(data, self.formula)
# Convert band data to masked array
result_data = numpy.ma.masked_values(
result.bands[0].data(),
result.bands[0].nodata_value,
)
# Apply rasterized geometry as mask if clip geometry was provided
if self.geom:
result_data = self.mask_by_geom(result, result_data)
yield result_data.compressed()
def get_tile(self, layer_id, zlevel=None):
"""
Returns a tile for rendering. If the tile does not exists, higher
level tiles are searched and warped to lower level if found.
"""
if self.is_pixel_request:
tilez = self.max_zoom
# Derive the tile index from the input coordinates.
xcoord = float(self.kwargs.get('xcoord'))
ycoord = float(self.kwargs.get('ycoord'))
bbox = [xcoord, ycoord, xcoord, ycoord]
indexrange = tile_index_range(bbox, tilez)
tilex = indexrange[0]
tiley = indexrange[1]
else:
# Get tile indices from the request url parameters.
tilez = int(self.kwargs.get('z'))
tilex = int(self.kwargs.get('x'))
tiley = int(self.kwargs.get('y'))
return get_raster_tile(layer_id, tilez, tilex, tiley)
def get(self, request):
# Initiate algebra parser
parser = RasterAlgebraParser()
# Get formula from request
formula = request.GET.get('formula')
# Get id list from request
ids = self.get_ids()
# Compute tile index range
zoom, xmin, ymin, xmax, ymax = self.get_tile_range()
# Check maximum size of target raster in pixels
max_pixels = getattr(settings, 'RASTER_EXPORT_MAX_PIXELS', EXPORT_MAX_PIXELS)
if WEB_MERCATOR_TILESIZE * (xmax - xmin) * WEB_MERCATOR_TILESIZE * (ymax - ymin) > max_pixels:
raise RasterAlgebraException('Export raster too large.')
# Construct an empty raster with the output dimensions
result_raster = self.construct_raster(zoom, xmin, xmax, ymin, ymax)
target = result_raster.bands[0]
# Get raster data as 1D arrays and store in dict that can be used
# for formula evaluation.
for xindex, x in enumerate(range(xmin, xmax + 1)):
for yindex, y in enumerate(range(ymin, ymax + 1)):
data = {}
for name, layerid in ids.items():
tile = get_raster_tile(layerid, zoom, x, y)
if tile:
data[name] = tile
# Ignore this tile if data is not found for all layers
if len(data) != len(ids):
continue
# Evaluate raster algebra expression, return 400 if not successful
try:
# Evaluate raster algebra expression
tile_result = parser.evaluate_raster_algebra(data, formula)
except:
raise RasterAlgebraException('Failed to evaluate raster algebra.')
# Update nodata value on target
target.nodata_value = tile_result.bands[0].nodata_value
# Update results raster with algebra
target.data(
data=tile_result.bands[0].data(),
size=(WEB_MERCATOR_TILESIZE, WEB_MERCATOR_TILESIZE),
offset=(xindex * WEB_MERCATOR_TILESIZE, yindex * WEB_MERCATOR_TILESIZE),
)
# Create filename base with datetime stamp
filename_base = 'algebra_export'
# Add name slug to filename if provided
if request.GET.get('filename', ''):
# Sluggify name
slug = slugify(request.GET.get('filename'))
# Remove all unwanted characters
slug = "".join([c for c in slug if re.match(r'\w|\-', c)])
# Limit length of custom name slug
slug = slug[:MAX_EXPORT_NAME_LENGTH]
# Add name slug to filename base
filename_base += '_' + slug
filename_base += '_{0}'.format(datetime.now().strftime('%Y_%m_%d_%H_%M'))
# Compress resulting raster file into a zip archive
raster_workdir = getattr(settings, 'RASTER_WORKDIR', None)
dest = NamedTemporaryFile(dir=raster_workdir, suffix='.zip')
dest_zip = zipfile.ZipFile(dest.name, 'w', allowZip64=True)
dest_zip.write(
filename=self.exportfile.name,
arcname=filename_base + '.tif',
compress_type=zipfile.ZIP_DEFLATED,
)
# Write README.txt and COLORMAP.txt files to zip file
self.write_readme(dest_zip)
self.write_colormap(dest_zip)
# Close zip file before returning
dest_zip.close()
# Create file based response containing zip file and return for download
response = FileResponse(
open(dest.name, 'rb'),
content_type='application/zip'
)
response['Content-Disposition'] = 'attachment; filename="{0}"'.format(filename_base + '.zip')
return response
def get_raster_tile(self, layerid, zoom, tilex, tiley):
return get_raster_tile(layerid, zoom, tilex, tiley)
