def to_svg(geometries, envelope=None, max_width=300, max_height=300):
svg_top = '<svg xmlns="http://www.w3.org/2000/svg" ' \
'xmlns:xlink="http://www.w3.org/1999/xlink" '
if len(geometries) == 0:
return svg_top + '/>'
else:
geometry = GeometryCollection(geometries)
# Establish SVG canvas that will fit all the data + small space
xmin, ymin, xmax, ymax = geometry.bounds
if xmin == xmax and ymin == ymax:
# This is a point; buffer using an arbitrary size
xmin, ymin, xmax, ymax = geometry.buffer(1).bounds
else:
# Expand bounds by a fraction of the data ranges
expand = 0.04 # or 4%, same as R plots
widest_part = max([xmax - xmin, ymax - ymin])
expand_amount = widest_part * expand
xmin -= expand_amount
ymin -= expand_amount
xmax += expand_amount
ymax += expand_amount
dx = xmax - xmin
dy = ymax - ymin
width = min([max([100., dx]), max_width])
height = min([max([100., dy]), max_height])
try:
scale_factor = max([dx, dy]) / max([width, height])
except ZeroDivisionError:
scale_factor = 1.
view_box, transform = None, None
if envelope:
xxmin, yymin, xxmax, yymax = envelope.bounds
view_box = "{} {} {} {}".format(xxmin, yymin, xxmax - xxmin,
yymax - yymin)
transform = "matrix(1,0,0,-1,0,{})".format(yymax + yymin)
else:
view_box = "{} {} {} {}".format(xmin, ymin, dx, dy)
transform = "matrix(1,0,0,-1,0,{})".format(ymax + ymin)
l = []
for g in geometries:
svg = g.svg(scale_factor)
if hasattr(g, 'plot'):
xml = ElementTree.fromstring(svg)
for v in g.plot:
xml.set(v, g.plot[v])
svg = ElementTree.tostring(xml).decode()
l.append(svg)
body = '<g>' + ''.join(l) + '</g>'
return ('{0} width="{2}" height="{3}" viewBox="{1}" '
'preserveAspectRatio="xMidYMid meet">'
'<g transform="{4}">{5}</g></svg>').format(
svg_top, view_box, width, height, transform, body)
