Function for converting border polygon back to row/col

[scottstanie]

I was wondering if people thought it would be useful to add a function to raster_polygon like this:

def convert_boundary_to_pixels(filename, polygon):
    """Convert boundary polygon from projected to pixel coordinates.

    Parameters
    ----------
    filename: str
        Path to GDAL friendly file containing geocoded raster.
    polygon : shapely.geometry.Polygon
        Polygon object output by `get_boundary_polygon`

    Returns
    -------
    polygon : shapely.geometry.Polygon
        Same as `polygon` but with coordinates transformed to x/y (column, row).
    """
    ds = gdal.Open(filename, gdal.GA_ReadOnly)
    gt_inv = gdal.InvGeoTransform(ds.GetGeoTransform())
    ds = None

    xmin, xsize, _, ymin, _, ysize = gt_inv
    x, y = polygon.exterior.xy
    return Polygon(zip(np.array(x) * xsize + xmin, np.array(y) * ysize + ymin))

This would be so that a user can take the border polygon we produce and know where in the raster the nodata occurs.

[scottstanie]

On a related note, I noticed that get_boundary_polygon skips every 100 pixels in the implementation means that the corners get cut off

Did we intend for the border to be exact, or more of an "approximate placement" thing like ASF has on their search page?