katana in qgis 2

katana.py

"""
Split large polygons into smaller parts for faster intersections

https://snorfalorpagus.net/blog/2016/03/13/splitting-large-polygons-for-faster-intersections/
"""

##Input=vector
##Threshold=number 500.0
##Recursion=number 250
##Output=output vector

import processing
from qgis.core import QgsMessageLog
from qgis.core import QGis
from qgis.core import QgsGeometry, QgsPoint, QgsRectangle
from processing.tools.vector import VectorWriter

threshold = Threshold

layer_input = processing.getObject(Input)

data_provider = layer_input.dataProvider()
fields = data_provider.fields()
crs = data_provider.crs()

writer = VectorWriter(
    destination=Output,
    encoding=None,
    fields=fields,
    geometryType=QGis.WKBMultiPolygon,
    crs=crs
)

def katana(geom, threshold, count):
    bbox = geom.boundingBox()
    width = bbox.width()
    height = bbox.height()
    xmin = bbox.xMinimum()
    ymin = bbox.yMinimum()
    xmax = bbox.xMaximum()
    ymax = bbox.yMaximum()
    xcenter = xmin + width / 2.0
    ycenter = ymin + height / 2.0
    if max(width, height) <= threshold or count == Recursion:
        return [geom]
    if height >= width:
        # split left to right
        a = QgsGeometry.fromRect(QgsRectangle(xmin, ymin, xmax, ycenter))
        b = QgsGeometry.fromRect(QgsRectangle(xmin, ycenter, xmax, ymax))
    else:
        # split top to bottom
        a = QgsGeometry.fromRect(QgsRectangle(xmin, ymin, xcenter, ymax))
        b = QgsGeometry.fromRect(QgsRectangle(xcenter, ymin, xmax, ymax))
    result = []
    for d in (a, b,):
        c = geom.intersection(d)
        if c.isMultipart():
            for g in c.asGeometryCollection():
                result.extend(katana(g, threshold, count + 1))
        else:
            result.extend(katana(c, threshold, count + 1))
    return result

progress.setPercentage(0)
num_features = layer_input.featureCount()
for n, feature in enumerate(processing.features(layer_input)):
    geoms = katana(feature.geometry(), threshold, 0)
    for geom in geoms:
        feature.setGeometry(geom)
        writer.addFeature(feature)
    progress.setPercentage(int(100*(n+1)/float(num_features)))
progress.setPercentage(100)

del(katana)