Function to transform cv2 thesholdiag (black and white / binary image) to a group of polygons

threshold_to_polygon.py

import rasterio
from rasterio import features
import shapely
from shapely.geometry import Point, Polygon

def mask_to_polygons_layer(mask):
    all_polygons = []
    for shape, value in features.shapes(mask.astype(np.int16), mask=(mask >0), transform=rasterio.Affine(1.0, 0, 0, 0, 1.0, 0)):
        return shapely.geometry.shape(shape)
        all_polygons.append(shapely.geometry.shape(shape))

    all_polygons = shapely.geometry.MultiPolygon(all_polygons)
    if not all_polygons.is_valid:
        all_polygons = all_polygons.buffer(0)
        # Sometimes buffer() converts a simple Multipolygon to just a Polygon,
        # need to keep it a Multi throughout
        if all_polygons.type == 'Polygon':
            all_polygons = shapely.geometry.MultiPolygon([all_polygons])
    return all_polygons

polygons = mask_to_polygons_layer(threshold)