Generate mask data from a given raster data.

        Args:
            rasterfile: raster file path.
            outmaskfile: output mask file path.

        Returns:
            Raster object of mask data.

def get_mask_from_raster(rasterfile, outmaskfile, keep_nodata=False):
        """Generate mask data from a given raster data.

        Args:
            rasterfile: raster file path.
            outmaskfile: output mask file path.

        Returns:
            Raster object of mask data.
        """
        raster_r = RasterUtilClass.read_raster(rasterfile)
        xsize = raster_r.nCols
        ysize = raster_r.nRows
        nodata_value = raster_r.noDataValue
        srs = raster_r.srs
        x_min = raster_r.xMin
        y_max = raster_r.yMax
        dx = raster_r.dx
        data = raster_r.data

        if not keep_nodata:
            i_min = ysize - 1
            i_max = 0
            j_min = xsize - 1
            j_max = 0
            for i in range(ysize):
                for j in range(xsize):
                    if abs(data[i][j] - nodata_value) > DELTA:
                        i_min = min(i, i_min)
                        i_max = max(i, i_max)
                        j_min = min(j, j_min)
                        j_max = max(j, j_max)

            # print(i_min, i_max, j_min, j_max)
            y_size_mask = i_max - i_min + 1
            x_size_mask = j_max - j_min + 1
            x_min_mask = x_min + j_min * dx
            y_max_mask = y_max - i_min * dx
        else:
            y_size_mask = ysize
            x_size_mask = xsize
            x_min_mask = x_min
            y_max_mask = y_max
            i_min = 0
            j_min = 0
        print('%dx%d -> %dx%d' % (xsize, ysize, x_size_mask, y_size_mask))

        mask = numpy.zeros((y_size_mask, x_size_mask))

        for i in range(y_size_mask):
            for j in range(x_size_mask):
                if abs(data[i + i_min][j + j_min] - nodata_value) > DELTA:
                    mask[i][j] = 1
                else:
                    mask[i][j] = DEFAULT_NODATA

        mask_geotrans = [x_min_mask, dx, 0, y_max_mask, 0, -dx]
        RasterUtilClass.write_gtiff_file(outmaskfile, y_size_mask, x_size_mask, mask,
                                         mask_geotrans, srs, DEFAULT_NODATA, GDT_Int32)
        return Raster(y_size_mask, x_size_mask, mask, DEFAULT_NODATA, mask_geotrans, srs)