grass.pygrass.raster.segment — GRASS Python Library documentation

# 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

    class Segment:
        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 int(
                ((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()
            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 = 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()

        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)

Help Index | Topics Index | Keywords Index | Full Index

© 2003-2026 GRASS Development Team, GRASS GIS 8.4.3dev Reference Manual