geotiff_to_svg.py

# generates an svg topographical map from a GeoTIFF file. 

import rasterio
from shapely.geometry import Point, LineString
from skimage.measure import find_contours
from numpy import rot90, fliplr, flipud 
# this data was downloaded from https://maps.canada.ca/czs/index-en.html
fp = r'dataset/DEM.tif'
dataset = rasterio.open(fp)
_min = None
_max = None
simplify_tolerance = 2
levels = 5
colors = ["264653", "2a9d8f", "e9c46a", "f4a261", "e76f51"] 
ofh = open(f"halifax_{levels}_{simplify_tolerance}.svg", "w")
ofh.write("<svg>")
band1 = dataset.read(1)
band1 = rot90(band1)
band1 = flipud(band1)
for i in range(0, levels):
    path = ""
    shapes = find_contours(band1, i*150.0/levels)
    for shape in shapes:
        if len(shape) <= 3:
            continue
        ply = LineString([Point(_point) for _point in shape])
        ply = ply.simplify(simplify_tolerance)
        for point_i,point in enumerate(ply.coords):
            if point_i==0:
                path += f"M {point[0]} {point[1]} "
            else:
                path += f"L {point[0]} {point[1]} "
    path += "z"    
    _svg_str = f"<path fill=\"none\" stroke=\"#{colors[i % len(colors)]}\" d=\"{path}\" />\n"    
    print(_svg_str)
    ofh.write(_svg_str)
ofh.write("</svg>")
ofh.close()