Geografic-Information-System/lib/python/pygrass/modules/grid/split.py

# -*- coding: utf-8 -*-
"""
Created on Tue Apr  2 19:00:15 2013

@author: pietro
"""
from grass.pygrass.gis.region import Region
from grass.pygrass.vector.basic import Bbox


def get_bbox(reg, row, col, width, height, overlap):
    """Return a Bbox"""
    north = reg.north - (row * height - overlap) * reg.nsres
    south = reg.north - ((row + 1) * height + overlap) * reg.nsres
    east = reg.west + ((col + 1) * width + overlap) * reg.ewres
    west = reg.west + (col * width - overlap) * reg.ewres
    return Bbox(north=north if north <= reg.north else reg.north,
                south=south if south >= reg.south else reg.south,
                east=east if east <= reg.east else reg.east,
                west=west if west >= reg.west else reg.west,)


def split_region_tiles(region=None, width=100, height=100, overlap=0):
    """Spit a region into a list of Bbox. ::

        >>> reg = Region()
        >>> reg.north = 1350
        >>> reg.south = 0
        >>> reg.nsres = 1
        >>> reg.east = 1500
        >>> reg.west = 0
        >>> reg.ewres = 1
        >>> reg.cols
        1500
        >>> reg.rows
        1350
        >>> split_region_tiles(region=reg, width=1000, height=700, overlap=0)
        [[Bbox(1350.0, 650.0, 1000.0, 0.0), Bbox(1350.0, 650.0, 1500.0, 1000.0)],
         [Bbox(650.0, 0.0, 1000.0, 0.0), Bbox(650.0, 0.0, 1500.0, 1000.0)]]
        >>> split_region_tiles(region=reg, width=1000, height=700, overlap=10)
        [[Bbox(1350.0, 640.0, 1010.0, 0.0), Bbox(1350.0, 640.0, 1500.0, 990.0)],
         [Bbox(660.0, 0.0, 1010.0, 0.0), Bbox(660.0, 0.0, 1500.0, 990.0)]]
    """
    reg = region if region else Region()
    ncols = (reg.cols + width - 1) // width
    nrows = (reg.rows + height - 1) // height
    box_list = []
    #print reg
    for row in xrange(nrows):
        row_list = []
        for col in xrange(ncols):
            #print 'c', c, 'r', r
            row_list.append(get_bbox(reg, row, col, width, height, overlap))
        box_list.append(row_list)
    return box_list