[Bounded random points] Generate random points using a rasterio dataset as boundary #rasterio #numpy #algorithms

generate_random_points.py

def generate_random_points(r, num_points):
    """
    Generate random points with replacement using a raster as a bound.  Points
    will be the centers of pixels in the raster

    Parameters
    ----------
    r: rasterio.RasterReader
        The raster to use as the bounding area
    num_points: int
        The number of points to generate

    Returns
    -------
    points: list of tuples
        The X,Y coordinates of random pixel centers
    """
    # Get dimensions and cellsize of raster
    w, h = r.meta['width'], r.meta['height']
    cs = r.affine.a / 2.0

    # Create the functions to generate the random points 
    rand = lambda lim: np.random.randint(lim)
    to_xy = lambda rc: r.ul(*rc)
    center = lambda xy: (xy[0] + cs, xy[1] - cs)

    # Generate the list of points
    return [center(to_xy(((rand(h), rand(w))))) for i in xrange(num_points)]