Source code for grass.pygrass.raster.segment

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

[docs]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())
[docs] def rows(self): return libraster.Rast_window_rows()
[docs] def cols(self): return libraster.Rast_window_cols()
[docs] def nseg(self): rows = self.rows() cols = self.cols() return int( ((rows + self.srows - 1) / self.srows) * ((cols + self.scols - 1) / self.scols) )
[docs] 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
[docs] 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() libseg.Segment_open( self.c_seg, file_name, self.rows(), self.cols(), self.srows, self.scols, size, self.nseg(), ) self.flush()
[docs] 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 = open(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()
[docs] def init(self, mapobj, file_name=""): if file_name == "": file_name = mapobj.temp_file = open(file_name, "w") libseg.Segment_init(self.c_seg, mapobj.temp_file.fileno(), self.segments_in_mem)
[docs] 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
[docs] 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)
[docs] 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
[docs] 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)
[docs] 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
[docs] 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)
[docs] def close(self): """Free memory allocated to segment and delete temp file.""" libseg.Segment_close(self.c_seg)
[docs] 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)