diff --git a/cairosvg/helpers.py b/cairosvg/helpers.py
index ec254c49..a2b440cf 100644
--- a/cairosvg/helpers.py
+++ b/cairosvg/helpers.py
@@ -113,15 +113,17 @@ def point_angle(cx, cy, px, py):
     return atan2(py - cy, px - cx)
 
 
-def preserve_ratio(surface, node):
+def preserve_ratio(surface, node, width=None, height=None):
     """Manage the ratio preservation."""
     if node.tag == 'marker':
-        width = size(surface, node.get('markerWidth', '3'), 'x')
-        height = size(surface, node.get('markerHeight', '3'), 'y')
+        width = width or size(surface, node.get('markerWidth', '3'), 'x')
+        height = height or size(surface, node.get('markerHeight', '3'), 'y')
         _, _, viewbox = node_format(surface, node)
         viewbox_width, viewbox_height = viewbox[2:]
     elif node.tag in ('svg', 'image', 'g'):
-        width, height, _ = node_format(surface, node)
+        node_width, node_height, _ = node_format(surface, node)
+        width = width or node_width
+        height = height or node_height
         viewbox_width, viewbox_height = node.image_width, node.image_height
 
     translate_x = 0
diff --git a/cairosvg/surface.py b/cairosvg/surface.py
index 69b08bbb..47ce32af 100644
--- a/cairosvg/surface.py
+++ b/cairosvg/surface.py
@@ -190,12 +190,6 @@ def __init__(self, tree, output, dpi, parent_surface=None,
         self.stroke_and_fill = True
         width, height, viewbox = node_format(self, tree)
 
-        # If one of output_width or output_height is set, compute the scale
-        if output_width:
-            scale = output_width / width
-        elif output_height:
-            scale = output_height / height
-
         if output_width and output_height:
             width, height = output_width, output_height
         else:
@@ -246,7 +240,8 @@ def set_context_size(self, width, height, viewbox, scale, tree):
             tree.image_width = width
             tree.image_height = height
 
-        scale_x, scale_y, translate_x, translate_y = preserve_ratio(self, tree)
+        scale_x, scale_y, translate_x, translate_y = preserve_ratio(
+            self, tree, width, height)
         rect_x, rect_y = rect_x * scale_x, rect_y * scale_y
         rect_width, rect_height = width, height
         self.context.translate(*self.context.get_current_point())