def generate_footprint_wkt(ds, simplification_factor=2):
""" Generate a fooptrint from a raster, using black/no-data as exclusion
"""
# create an empty boolean array initialized as 'False' to store where
# values exist as a mask array.
nodata_map = np.zeros((ds.RasterYSize, ds.RasterXSize), dtype=np.bool)
for idx in range(1, ds.RasterCount + 1):
band = ds.GetRasterBand(idx)
raster_data = band.ReadAsArray()
nodata = band.GetNoDataValue()
if nodata is None:
nodata = 0
# apply the output to the map
nodata_map |= (raster_data != nodata)
# create a temporary in-memory dataset and write the nodata mask
# into its single band
with temporary_dataset(ds.RasterXSize + 2, ds.RasterYSize + 2, 1,
gdal.GDT_Byte) as tmp_ds:
copy_projection(ds, tmp_ds)
tmp_band = tmp_ds.GetRasterBand(1)
tmp_band.WriteArray(nodata_map.astype(np.uint8))
# create an OGR in memory layer to hold the created polygon
sr = osr.SpatialReference()
sr.ImportFromWkt(ds.GetProjectionRef())
ogr_ds = ogr.GetDriverByName('Memory').CreateDataSource('out')
layer = ogr_ds.CreateLayer('poly', sr.sr, ogr.wkbPolygon)
fd = ogr.FieldDefn('DN', ogr.OFTInteger)
layer.CreateField(fd)
# polygonize the mask band and store the result in the OGR layer
gdal.Polygonize(tmp_band, tmp_band, layer, 0)
if layer.GetFeatureCount() != 1:
# if there is more than one polygon, compute the minimum bounding polygon
geometry = ogr.Geometry(ogr.wkbPolygon)
while True:
feature = layer.GetNextFeature()
if not feature:
break
geometry = geometry.Union(feature.GetGeometryRef())
# TODO: improve this for a better minimum bounding polygon
geometry = geometry.ConvexHull()
else:
# obtain geometry from the first (and only) layer
feature = layer.GetNextFeature()
geometry = feature.GetGeometryRef()
if geometry.GetGeometryType() not in (ogr.wkbPolygon, ogr.wkbMultiPolygon):
raise RuntimeError("Error during poligonization. Wrong geometry "
"type.")
# check if reprojection to latlon is necessary
if not sr.IsGeographic():
dst_sr = osr.SpatialReference()
dst_sr.ImportFromEPSG(4326)
try:
geometry.TransformTo(dst_sr.sr)
except RuntimeError:
geometry.Transform(osr.CoordinateTransformation(sr.sr, dst_sr.sr))
gt = ds.GetGeoTransform()
resolution = min(abs(gt[1]), abs(gt[5]))
simplification_value = simplification_factor * resolution
# simplify the polygon. the tolerance value is *really* vague
try:
# SimplifyPreserveTopology() available since OGR 1.9.0
geometry = geometry.SimplifyPreserveTopology(simplification_value)
except AttributeError:
# use GeoDjango bindings if OGR is too old
geometry = ogr.CreateGeometryFromWkt(
GEOSGeometry(geometry.ExportToWkt()).simplify(
simplification_value, True).wkt)
return geometry.ExportToWkt()
def process(self,
input_filename,
output_filename,
geo_reference=None,
generate_metadata=True,
merge_with=None,
original_footprint=None):
# open the dataset and create an In-Memory Dataset as copy
# to perform optimizations
ds = create_mem_copy(gdal.Open(input_filename))
gt = ds.GetGeoTransform()
footprint_wkt = None
if not geo_reference:
if gt == (0.0, 1.0, 0.0, 0.0, 0.0, 1.0):
if ds.GetGCPCount() > 0:
geo_reference = InternalGCPs()
else:
raise ValueError("No geospatial reference for "
"unreferenced dataset given.")
if geo_reference:
logger.debug("Applying geo reference '%s'." %
type(geo_reference).__name__)
# footprint is always in EPSG:4326
ds, footprint_wkt = geo_reference.apply(ds)
# apply optimizations
for optimization in self.get_optimizations(ds):
logger.debug("Applying optimization '%s'." %
type(optimization).__name__)
try:
new_ds = optimization(ds)
if new_ds is not ds:
# cleanup afterwards
cleanup_temp(ds)
ds = new_ds
except:
cleanup_temp(ds)
raise
# generate the footprint from the dataset
if not footprint_wkt:
logger.debug("Generating footprint.")
footprint_wkt = self._generate_footprint_wkt(ds)
# check that footprint is inside of extent of generated image
# regenerate otherwise
else:
tmp_extent = getExtentFromRectifiedDS(ds)
tmp_bbox = Polygon.from_bbox(
(tmp_extent[0], tmp_extent[1], tmp_extent[2], tmp_extent[3]))
# transform image bbox to EPSG:4326 if necessary
proj = ds.GetProjection()
srs = osr.SpatialReference()
try:
srs.ImportFromWkt(proj)
srs.AutoIdentifyEPSG()
ptype = "PROJCS" if srs.IsProjected() else "GEOGCS"
srid = int(srs.GetAuthorityCode(ptype))
if srid != '4326':
out_srs = osr.SpatialReference()
out_srs.ImportFromEPSG(4326)
transform = osr.CoordinateTransformation(srs, out_srs)
tmp_bbox2 = ogr.CreateGeometryFromWkt(tmp_bbox.wkt)
tmp_bbox2.Transform(transform)
tmp_bbox = GEOSGeometry(tmp_bbox2.ExportToWkt())
except (RuntimeError, TypeError), e:
logger.warn("Projection: %s" % proj)
logger.warn("Failed to identify projection's EPSG code."
"%s: %s" % (type(e).__name__, str(e)))
tmp_footprint = GEOSGeometry(footprint_wkt)
if not tmp_bbox.contains(tmp_footprint):
logger.debug("Re-generating footprint because not inside of "
"generated image.")
footprint_wkt = tmp_footprint.intersection(tmp_bbox).wkt
def _generate_footprint_wkt(self, ds):
""" Generate a footprint from a raster, using black/no-data as
exclusion
"""
# create an empty boolean array initialized as 'False' to store where
# values exist as a mask array.
nodata_map = numpy.zeros((ds.RasterYSize, ds.RasterXSize),
dtype=numpy.bool)
for idx in range(1, ds.RasterCount + 1):
band = ds.GetRasterBand(idx)
raster_data = band.ReadAsArray()
nodata = band.GetNoDataValue()
if nodata is None:
nodata = 0
# apply the output to the map
nodata_map |= (raster_data != nodata)
# create a temporary in-memory dataset and write the nodata mask
# into its single band
tmp_ds = create_mem(ds.RasterXSize + 2, ds.RasterYSize + 2, 1,
gdal.GDT_Byte)
copy_projection(ds, tmp_ds)
tmp_band = tmp_ds.GetRasterBand(1)
tmp_band.WriteArray(nodata_map.astype(numpy.uint8))
# Remove unwanted small areas of nodata
# www.gdal.org/gdal__alg_8h.html#a33309c0a316b223bd33ae5753cc7f616
no_pixels = tmp_ds.RasterXSize * tmp_ds.RasterYSize
threshold = 4
max_threshold = (no_pixels / 16)
if self.sieve_max_threshold > 0:
max_threshold = self.sieve_max_threshold
while threshold <= max_threshold and threshold < 2147483647:
gdal.SieveFilter(tmp_band, None, tmp_band, threshold, 4)
threshold *= 4
#for debugging:
#gdal.GetDriverByName('GTiff').CreateCopy('/tmp/test.tif', tmp_ds)
# create an OGR in memory layer to hold the created polygon
sr = osr.SpatialReference()
sr.ImportFromWkt(ds.GetProjectionRef())
ogr_ds = ogr.GetDriverByName('Memory').CreateDataSource('out')
layer = ogr_ds.CreateLayer('poly', sr, ogr.wkbPolygon)
fd = ogr.FieldDefn('DN', ogr.OFTInteger)
layer.CreateField(fd)
# polygonize the mask band and store the result in the OGR layer
gdal.Polygonize(tmp_band, tmp_band, layer, 0)
tmp_ds = None
if layer.GetFeatureCount() > 1:
# if there is more than one polygon, compute the minimum
# bounding polygon
logger.debug("Merging %s features in footprint." %
layer.GetFeatureCount())
# union all features in one multi-polygon
geometry = ogr.Geometry(ogr.wkbMultiPolygon)
while True:
feature = layer.GetNextFeature()
if not feature:
break
geometry.AddGeometry(feature.GetGeometryRef())
geometry = geometry.UnionCascaded()
# TODO: improve this for a better minimum bounding polygon
geometry = geometry.ConvexHull()
elif layer.GetFeatureCount() < 1:
# there was an error during polygonization
raise RuntimeError("Error during polygonization. No feature "
"obtained.")
else:
# obtain geometry from the first (and only) layer
feature = layer.GetNextFeature()
geometry = feature.GetGeometryRef()
if geometry.GetGeometryType() != ogr.wkbPolygon:
raise RuntimeError(
"Error during polygonization. Wrong geometry "
"type: %s" %
ogr.GeometryTypeToName(geometry.GetGeometryType()))
# check if reprojection to latlon is necessary
if not sr.IsGeographic():
dst_sr = osr.SpatialReference()
dst_sr.ImportFromEPSG(4326)
try:
geometry.TransformTo(dst_sr)
except RuntimeError:
geometry.Transform(osr.CoordinateTransformation(sr, dst_sr))
gt = ds.GetGeoTransform()
resolution = min(abs(gt[1]), abs(gt[5]))
simplification_value = self.simplification_factor * resolution
#for debugging:
#geometry.GetGeometryRef(0).GetPointCount()
# simplify the polygon. the tolerance value is *really* vague
try:
# SimplifyPreserveTopology() available since OGR 1.9.0
geometry = geometry.SimplifyPreserveTopology(simplification_value)
except AttributeError:
# use GeoDjango bindings if OGR is too old
geometry = ogr.CreateGeometryFromWkt(
GEOSGeometry(geometry.ExportToWkt()).simplify(
simplification_value, True).wkt)
return geometry.ExportToWkt()
def __init__(self, src, dst):
self.fwd = osr.CoordinateTransformation(src, dst)
self.bwd = osr.CoordinateTransformation(dst, src)