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# -*- coding: utf-8 -*-
"""
Created on Mon Jun 11 18:02:27 2012
@author: pietro
"""
import ctypes
import grass.lib.gis as libgis
import grass.lib.raster as libraster
import grass.lib.segment as libseg
from grass.pygrass.raster.raster_type import TYPE as RTYPE
class Segment(object):
def __init__(self, srows=64, scols=64, maxmem=100):
self.srows = srows
self.scols = scols
self.maxmem = maxmem
self.c_seg = ctypes.pointer(libseg.SEGMENT())
def rows(self):
return libraster.Rast_window_rows()
def cols(self):
return libraster.Rast_window_cols()
def nseg(self):
rows = self.rows()
cols = self.cols()
return ((rows + self.srows - 1) / self.srows) * \
((cols + self.scols - 1) / self.scols)
def segments_in_mem(self):
if self.maxmem > 0 and self.maxmem < 100:
seg_in_mem = (self.maxmem * self.nseg()) / 100
else:
seg_in_mem = 4 * (self.rows() / self.srows +
self.cols() / self.scols + 2)
if seg_in_mem == 0:
seg_in_mem = 1
return seg_in_mem
def open(self, mapobj):
"""Open a segment it is necessary to pass a RasterSegment object.
"""
self.val = RTYPE[mapobj.mtype]['grass def']()
size = ctypes.sizeof(RTYPE[mapobj.mtype]['ctypes'])
file_name = libgis.G_tempfile()
#import pdb; pdb.set_trace()
libseg.Segment_open(self.c_seg, file_name,
self.rows(), self.cols(),
self.srows, self.scols,
size,
self.nseg())
self.flush()
def format(self, mapobj, file_name='', fill=True):
"""The segmentation routines require a disk file to be used for paging
segments in and out of memory. This routine formats the file open for
write on file descriptor fd for use as a segment file.
"""
if file_name == '':
file_name = libgis.G_tempfile()
mapobj.temp_file = file(file_name, 'w')
size = ctypes.sizeof(RTYPE[mapobj.mtype]['ctypes'])
if fill:
libseg.Segment_format(mapobj.temp_file.fileno(), self.rows(),
self.cols(), self.srows, self.scols, size)
else:
libseg.Segment_format_nofill(mapobj.temp_file.fileno(),
self.rows(), self.cols(),
self.srows, self.scols, size)
# TODO: why should I close and then re-open it?
mapobj.temp_file.close()
def init(self, mapobj, file_name=''):
if file_name == '':
file_name = mapobj.temp_file.name
mapobj.temp_file = open(file_name, 'w')
libseg.Segment_init(self.c_seg, mapobj.temp_file.fileno(),
self.segments_in_mem)
def get_row(self, row_index, buf):
"""Return the row using, the `segment` method"""
libseg.Segment_get_row(self.c_seg, buf.p, row_index)
return buf
def put_row(self, row_index, buf):
"""Write the row using the `segment` method"""
libseg.Segment_put_row(self.c_seg, buf.p, row_index)
def get(self, row_index, col_index):
"""Return the value of the map
"""
libseg.Segment_get(self.c_seg,
ctypes.byref(self.val), row_index, col_index)
return self.val.value
def put(self, row_index, col_index):
"""Write the value to the map
"""
libseg.Segment_put(self.c_seg,
ctypes.byref(self.val), row_index, col_index)
def get_seg_number(self, row_index, col_index):
"""Return the segment number
"""
return row_index / self.srows * self.cols / self.scols + \
col_index / self.scols
def flush(self):
"""Flush pending updates to disk.
Forces all pending updates generated by Segment_put() to be written to
the segment file seg. Must be called after the final Segment_put()
to force all pending updates to disk. Must also be called before the
first call to Segment_get_row."""
libseg.Segment_flush(self.c_seg)
def close(self):
"""Free memory allocated to segment and delete temp file. """
libseg.Segment_close(self.c_seg)
def release(self):
"""Free memory allocated to segment.
Releases the allocated memory associated with the segment file seg.
Note: Does not close the file. Does not flush the data which may be
pending from previous Segment_put() calls."""
libseg.Segment_release(self.c_seg)
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