preserveAspectRatio (#641)

lib/svg/units.py

@@ -127,6 +127,17 @@ def get_viewbox_transform(node):
     try:
         sx = doc_width / float(viewbox[2])
         sy = doc_height / float(viewbox[3])
+
+        # preserve aspect ratio
+        aspect_ratio = node.get('preserveAspectRatio', 'xMidYMid meet')
+        if aspect_ratio != 'none':
+            unit = parse_length_with_units(node.get('width'))[1]
+            if float(viewbox[2]) > parse_length_with_units(node.get('width'))[0]:
+                sx = convert_length(viewbox[2] + unit) / float(viewbox[2]) if 'slice' in aspect_ratio else 1.0
+            if float(viewbox[3]) > parse_length_with_units(node.get('height'))[0]:
+                sy = convert_length(viewbox[3] + unit) / float(viewbox[3]) if 'slice' in aspect_ratio else 1.0
+            sx = sy = max(sx, sy) if 'slice' in aspect_ratio else min(sx, sy)
+
         scale_transform = simpletransform.parseTransform("scale(%f, %f)" % (sx, sy))
         transform = simpletransform.composeTransform(transform, scale_transform)
     except ZeroDivisionError: