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Add balance by area mode

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This mode attempts to assign colors in such a way that the total
area of features assigned to each color class is balanced. It helps
avoid larger features causing a single color class to appear more
dominant on a colored map.
This commit is contained in:
Nyall Dawson 2017-02-17 10:51:50 +10:00
parent ac5e292243
commit ff10cf48f4
1 changed files with 45 additions and 17 deletions
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62
python/plugins/processing/algs/qgis/TopoColors.py
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@ -27,6 +27,8 @@ __revision__ = '$Format:%H$'
import os
import operator
from enum import Enum
from collections import defaultdict, deque
from qgis.core import (QgsField,
@ -37,19 +39,26 @@ from qgis.core import (QgsField,
from qgis.PyQt.QtCore import (QVariant)
from processing.core.GeoAlgorithm import GeoAlgorithm
from processing.core.parameters import ParameterVector
from processing.core.parameters import ParameterNumber
from processing.core.parameters import (ParameterVector,
ParameterSelection,
ParameterNumber)
from processing.core.outputs import OutputVector
from processing.tools import dataobjects, vector
pluginPath = os.path.split(os.path.split(os.path.dirname(__file__))[0])[0]
class BalanceMethod(Enum):
BY_COUNT = 0
BY_AREA = 1
BY_DISTANCE = 2
class TopoColor(GeoAlgorithm):
INPUT_LAYER = 'INPUT_LAYER'
MIN_COLORS='MIN_COLORS'
BALANCE='BALANCE'
OUTPUT_LAYER = 'OUTPUT_LAYER'
def defineCharacteristics(self):
self.name, self.i18n_name = self.trAlgorithm('Topological coloring')
self.group, self.i18n_group = self.trAlgorithm('Cartographic tools')
@ -59,6 +68,13 @@ class TopoColor(GeoAlgorithm):
self.tr('Input layer'), [dataobjects.TYPE_VECTOR_POLYGON]))
self.addParameter(ParameterNumber(self.MIN_COLORS,
self.tr('Minimum number of colors'), 1, 1000, 4))
balance_by = [self.tr('By feature count'),
self.tr('By assigned area'),
self.tr('By distance between colors')]
self.addParameter(ParameterSelection(
self.BALANCE,
self.tr('Balance color assignment'),
balance_by))
self.addOutput(OutputVector(self.OUTPUT_LAYER, self.tr('Colored'), datatype=[dataobjects.TYPE_VECTOR_POLYGON]))
@ -66,6 +82,7 @@ class TopoColor(GeoAlgorithm):
layer = dataobjects.getObjectFromUri(
self.getParameterValue(self.INPUT_LAYER))
min_colors = self.getParameterValue(self.MIN_COLORS)
balance_by = BalanceMethod(self.getParameterValue(self.BALANCE))
fields = layer.fields()
fields.append(QgsField('color_id', QVariant.Int))
@ -76,13 +93,13 @@ class TopoColor(GeoAlgorithm):
layer.wkbType(),
layer.crs())
# use a deque so we can drop features as we write them
# it's a bit friendlier on memory usage
features = deque(f for f in vector.features(layer))
features = {f.id():f for f in vector.features(layer)}
topology, id_graph = self.compute_graph(features, feedback)
feature_colors = ColoringAlgorithm.balanced(topology,
feedback,
feature_colors = ColoringAlgorithm.balanced(features,
balance=balance_by,
graph=topology,
feedback=feedback,
min_colors=min_colors)
max_colors = max(feature_colors.values())
@ -90,12 +107,11 @@ class TopoColor(GeoAlgorithm):
total = 20.0 / len(features)
current = 0
while features:
input_feature = features.popleft()
for feature_id, input_feature in features.items():
output_feature = input_feature
attributes = input_feature.attributes()
if input_feature.id() in feature_colors:
attributes.append(feature_colors[input_feature.id()])
if feature_id in feature_colors:
attributes.append(feature_colors[feature_id])
else:
attributes.append(NULL)
output_feature.setAttributes(attributes)
@ -115,7 +131,7 @@ class TopoColor(GeoAlgorithm):
id_graph = Graph(sort_graph=True)
# skip features without geometry
features_with_geometry = dict((f.id(), f) for f in features if f.hasGeometry())
features_with_geometry = { f_id: f for (f_id, f) in features.items() if f.hasGeometry() }
total = 70.0 / len(features_with_geometry)
index = QgsSpatialIndex()
@ -151,7 +167,7 @@ class TopoColor(GeoAlgorithm):
class ColoringAlgorithm:
@staticmethod
def balanced(graph, feedback, min_colors = 4):
def balanced(features, graph, feedback, balance=BalanceMethod.BY_COUNT, min_colors = 4):
feature_colors = {}
# start with minimum number of colors in pool
color_pool = set(range(1, min_colors+1))
@ -167,8 +183,10 @@ class ColoringAlgorithm:
reverse=True)]
# counts for each color already assigned
color_counts = defaultdict(int)
color_areas = defaultdict(float)
for c in color_pool:
color_counts[c] = 0
color_areas[c] = 0
total = 10.0 / len(sorted_by_count)
i = 0
@ -183,16 +201,26 @@ class ColoringAlgorithm:
# from the existing colors, work out which are available (ie non-adjacent)
available_colors = color_pool.difference(adjacent_colors)
feature_color=-1
if len(available_colors) == 0:
# no existing colors available for this feature, so add new color to pool
feature_color = len(color_pool) + 1
color_pool.add(feature_color)
else:
# choose least used available color
counts = [(c, v) for c, v in color_counts.items() if c in available_colors]
feature_color = sorted(counts, key=operator.itemgetter(1))[0][0]
if balance==BalanceMethod.BY_COUNT:
# choose least used available color
counts = [(c, v) for c, v in color_counts.items() if c in available_colors]
feature_color = sorted(counts, key=operator.itemgetter(1))[0][0]
color_counts[feature_color] += 1
elif balance==BalanceMethod.BY_AREA:
areas = [(c, v) for c, v in color_areas.items() if c in available_colors]
feature_color = sorted(areas, key=operator.itemgetter(1))[0][0]
color_areas[feature_color] += features[feature_id].geometry().area()
#elif balance==BalanceMethod.BY_DISTANCE:
feature_colors[feature_id] = feature_color
color_counts[feature_color] += 1
i += 1
feedback.setProgress(70 + int(i * total))