def make_map(map_output, scale=20000, x_center=622000, y_center=6406000):
"Make a map as a function of the scale"
# Compute the scale
page_size = int(PAGE_FORMAT[1])
f = math.sqrt(2)**PAGES[page_size]
# increasing map_x and map_y lead to decreasing font and symbol size: not good
map_x = int(f * 4600) # 4600 is the number of pixels for an A4 length
# if 460: zoom = 13
map_y = int(map_x / math.sqrt(2))
m = Map(map_x, map_y)
load_map(m, MAPNIK_FILE)
# Bounding box (expressed in EPSG:3857, meters)
delta_x = f * 0.295 * scale / math.cos(LATITUDE * 2 * math.pi / 360)
delta_y = delta_x / math.sqrt(2)
xmin = x_center - delta_x / 2
xmax = x_center + delta_x / 2
ymin = y_center - delta_y / 2
ymax = y_center + delta_y / 2
bbox = (Envelope(xmin, ymin, xmax, ymax))
m.zoom_to_box(bbox)
print("Scale = " + str(m.scale()))
render_to_file(m, map_output)
