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views.py
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views.py
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from __future__ import unicode_literals
import json
import re
import zipfile
from datetime import datetime
from tempfile import NamedTemporaryFile
import numpy
from PIL import Image
from django.conf import settings
from django.contrib.gis.gdal import GDALRaster
from django.contrib.gis.geos import Polygon
from django.db.models import Q
from django.http import FileResponse, Http404, HttpResponse
from django.shortcuts import get_object_or_404
from django.template.defaultfilters import slugify
from django.utils import six
from django.views.generic import View
from raster.algebra.const import ALGEBRA_PIXEL_TYPE_GDAL
from raster.algebra.parser import RasterAlgebraParser
from raster.const import DEFAULT_LEGEND_BREAKS, EXPORT_MAX_PIXELS, IMG_FORMATS, MAX_EXPORT_NAME_LENGTH, README_TEMPLATE
from raster.exceptions import RasterAlgebraException
from raster.models import Legend, RasterLayer
from raster.tiles.const import WEB_MERCATOR_SRID, WEB_MERCATOR_TILESIZE
from raster.tiles.utils import get_raster_tile, tile_bounds, tile_index_range, tile_scale
from raster.utils import band_data_to_image, hex_to_rgba
class RasterView(View):
def get_colormap(self, layer=None):
"""
Returns colormap from request and layer, looking for a colormap in
the request, a custom legend name to construct the legend or the
default colormap from the layer legend.
"""
if 'colormap' in self.request.GET:
colormap = self.request.GET['colormap']
colormap = json.loads(colormap)
colormap = {k: hex_to_rgba(v) if isinstance(v, (six.string_types, int)) else v for k, v in colormap.items()}
elif 'legend' in self.request.GET:
legend_input = self.request.GET['legend']
try:
legend_input = int(legend_input)
except ValueError:
pass
# Try to get legend by id, name or from input layer
if isinstance(legend_input, int):
legend = get_object_or_404(Legend, id=legend_input)
else:
legend = Legend.objects.filter(title__iexact=legend_input).first()
colormap = legend.colormap
elif layer and hasattr(layer.legend, 'colormap'):
colormap = layer.legend.colormap
elif layer:
# Construct a grayscale colormap from layer metadata
meta = layer.rasterlayerbandmetadata_set.first()
# Return if no metadata can be found to construct the colormap
if meta is None:
return
# Compute bin width for a linear scaling
diff = (meta.max - meta.min) / DEFAULT_LEGEND_BREAKS
# Create colormap with seven breaks
colormap = {}
for i in range(DEFAULT_LEGEND_BREAKS):
if i == 0:
expression = '({0} <= x) & (x <= {1})'
else:
expression = '({0} < x) & (x <= {1})'
expression = expression.format(meta.min + diff * i, meta.min + diff * (i + 1))
colormap[expression] = [(255 / (DEFAULT_LEGEND_BREAKS - 1)) * i] * 3 + [255, ]
else:
return
# Filter by custom entries if requested
if 'entries' in self.request.GET:
entries = self.request.GET['entries'].split(',')
colormap = {k: v for (k, v) in colormap.items() if str(k) in entries}
return colormap
def get_format(self):
"""
Returns image format requested.
"""
return IMG_FORMATS[self.kwargs.get('format')]
def write_img_to_response(self, img, stats):
"""
Writes rgba numpy array to http response.
"""
# Create response, and add image
response = HttpResponse()
frmt = self.get_format()
response['Content-Type'] = frmt
response['aggregation'] = json.dumps(stats)
img.save(response, frmt)
return response
def get_tile(self, layer_id):
"""
Returns a tile for rendering. If the tile does not exists, higher
level tiles are searched and warped to lower level if found.
"""
# Get tile indices from request
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_layer(self):
"""
Gets layer from request data trying both name and id.
"""
# Get layer query data from input
if 'layer' in self.kwargs:
data = self.kwargs.get('layer')
elif 'layer' in self.request.GET:
data = self.request.GET.get('layer')
else:
raise Http404
# Determine query paremeter type
try:
data = int(data)
query = Q(id=data)
except ValueError:
query = Q(rasterfile__contains='rasters/' + data)
return get_object_or_404(RasterLayer, query)
class AlgebraView(RasterView):
"""
A view to calculate map algebra on raster layers.
"""
def get_ids(self):
# Get layer ids
ids = self.request.GET.get('layers', '').split(',')
# Check if layer parameter is valid
if not len(ids) or not all('=' in idx for idx in ids):
raise RasterAlgebraException('Layer parameter is not valid.')
# Split id/name input pairs
ids = [idx.split('=') for idx in ids]
# Convert ids to integer
try:
ids = {idx[0]: int(idx[1]) for idx in ids}
except ValueError:
raise RasterAlgebraException('Layer parameter is not valid.')
return ids
def get(self, request, *args, **kwargs):
# Get layer ids
ids = self.get_ids()
# Get raster data as 1D arrays and store in dict that can be used
# for formula evaluation.
data = {}
for name, layerid in ids.items():
tile = self.get_tile(layerid)
if tile:
data[name] = tile
else:
# Create empty image if any layer misses the required tile
img = Image.new("RGBA", (WEB_MERCATOR_TILESIZE, WEB_MERCATOR_TILESIZE), (0, 0, 0, 0))
return self.write_img_to_response(img, {})
# Get formula from request
formula = request.GET.get('formula', None)
# Dispatch by request type. If a formula was provided, use raster
# algebra otherwise look for rgb request.
if formula:
return self.get_algebra(data, formula)
elif 'r' in data and 'g' in data and 'b' in data:
return self.get_rgb(data)
else:
raise RasterAlgebraException(
'Specify raster algebra formula or provide rgb layer keys.'
)
def get_algebra(self, data, formula):
parser = RasterAlgebraParser()
# Evaluate raster algebra expression, return 400 if not successful
try:
# Evaluate raster algebra expression
result = parser.evaluate_raster_algebra(data, formula)
except:
raise RasterAlgebraException('Failed to evaluate raster algebra.')
# Get array from algebra result
result = numpy.ma.masked_values(
result.bands[0].data(),
result.bands[0].nodata_value,
)
# Render tile
colormap = self.get_colormap()
if colormap:
# Render tile using the legend data
img, stats = band_data_to_image(result, colormap)
else:
# Scale to grayscale rgb (can be colorscheme later on)
result = result.astype('float').ravel()
result = 255 * (result - numpy.min(result)) / (numpy.max(result) - numpy.min(result))
# Create rgba matrix from grayscale array
result = numpy.array((result, result, result, numpy.repeat(255, len(result)))).T
rgba = result.reshape(WEB_MERCATOR_TILESIZE, WEB_MERCATOR_TILESIZE, 4).astype('uint8')
# Create image from array
img = Image.fromarray(rgba)
stats = {}
# Return rendered image
return self.write_img_to_response(img, stats)
def get_rgb(self, data):
red = data['r']
green = data['g']
blue = data['b']
red = red.bands[0].data()
green = green.bands[0].data()
blue = blue.bands[0].data()
scale = float(self.request.GET.get('scale', 255))
red[red > scale] = scale
green[green > scale] = scale
blue[blue > scale] = scale
red = red * 255.0 / scale
green = green * 255.0 / scale
blue = blue * 255.0 / scale
# Create zeros array.
alpha = 255 * (red > 0) * (blue > 0) * (green > 0)
rgba = numpy.array((red.ravel(), green.ravel(), blue.ravel(), alpha.ravel())).T
rgba = rgba.reshape(WEB_MERCATOR_TILESIZE, WEB_MERCATOR_TILESIZE, 4).astype('uint8')
# Create image from array
img = Image.fromarray(rgba)
stats = {}
# Return rendered image
return self.write_img_to_response(img, stats)
class TmsView(RasterView):
def get(self, *args, **kwargs):
"""
Returns an image rendered from a raster tile.
"""
# Get layer
layer = self.get_layer()
# Override color map if arg provided
colormap = self.get_colormap(layer)
# Get tile
tile = self.get_tile(layer.id)
# Render tile
if tile and colormap:
data = numpy.ma.masked_values(
tile.bands[0].data(),
tile.bands[0].nodata_value,
)
# Render tile using the legend data
img, stats = band_data_to_image(data, colormap)
else:
# Create empty image if tile cant be found
img = Image.new("RGBA", (WEB_MERCATOR_TILESIZE, WEB_MERCATOR_TILESIZE), (0, 0, 0, 0))
stats = {}
return self.write_img_to_response(img, stats)
class LegendView(RasterView):
def get(self, request, legend_id):
"""
Returns the legend for this layer as a json string. The legend is a list of
legend entries with the attributes "name", "expression" and "color".
"""
if(legend_id):
# Get legend from id
legend = get_object_or_404(Legend, id=legend_id)
else:
# Try to get legend from layer
lyr = self.get_layer()
if not lyr.legend:
raise Http404
legend = lyr.legend
return HttpResponse(legend.json, content_type='application/json')
class ExportView(AlgebraView):
def construct_raster(self, z, xmin, xmax, ymin, ymax):
"""
Create an empty tif raster file on disk using the input tile range. The
new raster aligns with the xyz tile scheme and can be filled
sequentially with raster algebra results.
"""
# Compute bounds and scale to construct raster.
bounds = []
for x in range(xmin, xmax + 1):
for y in range(ymin, ymax + 1):
bounds.append(tile_bounds(x, y, z))
bounds = [
min([bnd[0] for bnd in bounds]),
min([bnd[1] for bnd in bounds]),
max([bnd[2] for bnd in bounds]),
max([bnd[3] for bnd in bounds]),
]
scale = tile_scale(z)
# Create tempfile.
raster_workdir = getattr(settings, 'RASTER_WORKDIR', None)
self.exportfile = NamedTemporaryFile(dir=raster_workdir, suffix='.tif')
# Instantiate raster using the tempfile path.
return GDALRaster({
'srid': WEB_MERCATOR_SRID,
'width': (xmax - xmin + 1) * WEB_MERCATOR_TILESIZE,
'height': (ymax - ymin + 1) * WEB_MERCATOR_TILESIZE,
'scale': (scale, -scale),
'origin': (bounds[0], bounds[3]),
'driver': 'tif',
'bands': [{'data': [0], 'nodata_value': 0}],
'name': self.exportfile.name,
'datatype': ALGEBRA_PIXEL_TYPE_GDAL,
})
def get_tile_range(self):
"""
Compute a xyz tile range from the query parameters. If no bbox
parameter is found, the range defaults to the maximum extent of
all input raster layers.
"""
# Get raster layers
layers = RasterLayer.objects.filter(id__in=self.get_ids().values())
# Establish zoom level
if self.request.GET.get('zoom', None):
zlevel = int(self.request.GET.get('zoom'))
else:
# Get highest zoom level of all input layers
zlevel = max([layer.metadata.max_zoom for layer in layers])
# Use bounding box to compute tile range
if self.request.GET.get('bbox', None):
bbox = Polygon.from_bbox(self.request.GET.get('bbox').split(','))
bbox.srid = 4326
bbox.transform(WEB_MERCATOR_SRID)
tile_range = tile_index_range(bbox.extent, zlevel)
else:
# Get list of tile ranges
layer_ranges = []
for layer in layers:
layer_ranges.append(tile_index_range(layer.extent(), zlevel))
# Estabish overlap of tile index ranges
tile_range = [
min([rng[0] for rng in layer_ranges]),
min([rng[1] for rng in layer_ranges]),
max([rng[2] for rng in layer_ranges]),
max([rng[3] for rng in layer_ranges]),
]
return [zlevel, ] + tile_range
def write_colormap(self, zfile):
# Try to get colormap
colormap = self.get_colormap()
# Return early if colormap was not specified
if not colormap:
return
# Set a simple header for this colormap
colorstr = '# Raster Algebra Colormap\nINTERPOLATION:DISCRETE\n'
# Add expressions and colors of the colormap
for key, val in colormap.items():
colorstr += str(key) + ',' + ','.join((str(x) for x in val)) + ',' + str(key) + '\n'
# Write colormap file
zfile.writestr('COLORMAP.txt', colorstr)
def write_readme(self, zfile):
# Get tile index range
zoom, xmin, ymin, xmax, ymax = self.get_tile_range()
# Construct layer names string
layerstr = ''
for name, layerid in self.get_ids().items():
layer = RasterLayer.objects.get(id=layerid)
layerstr += '{layerid} "{name}" (Formula label: {label})\n'.format(
name=layer.name,
label=name,
layerid=layerid
)
# Get description, append newline if provided
description = self.request.GET.get('description', '')
if description:
description += '\n'
# Initiate metadata object
readmedata = {
'datetime': datetime.now().strftime('%Y-%m-%d at %H:%M'),
'url': self.request.build_absolute_uri(),
'bbox': self.request.GET.get('bbox', 'Minimum bounding-box covering all layers.'),
'formula': self.request.GET.get('formula'),
'zoom': str(zoom),
'xindexrange': '{} - {}'.format(xmin, xmax),
'yindexrange': '{} - {}'.format(ymin, ymax),
'layers': layerstr,
'description': description,
}
# Write readme file
readme = README_TEMPLATE.format(**readmedata)
zfile.writestr('README.txt', readme)
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