embroidery origin at canvas center and size canvas accordingly

embroider_input.py

@@ -37,12 +37,12 @@ def main(embroidery_file):
                                    stop=stitch.flags & STOP,
                                    trim=stitch.flags & TRIM)
 
-    dimensions = stitch_plan.dimensions
+    extents = stitch_plan.extents
     svg = etree.Element("svg", nsmap=inkex.NSS, attrib=
                         {
-                            "width": "%s" % dimensions[0],
-                            "height": "%s" % dimensions[1],
-                            "viewBox": "0 0 %s %s" % dimensions,
+                            "width": str(extents[0] * 2),
+                            "height": str(extents[1] * 2),
+                            "viewBox": "0 0 %s %s" % (extents[0] * 2, extents[1] * 2),
                         })
     render_stitch_plan(svg, stitch_plan)
 
@@ -51,6 +51,10 @@ def main(embroidery_file):
     layer.set(INKSCAPE_LABEL, os.path.basename(embroidery_file))
     layer.attrib.pop('id')
 
+    # Shift the design so that its origin is at the center of the canvas
+    # Note: this is NOT the same as centering the design in the canvas!
+    layer.set('transform', 'translate(%s,%s)' % (extents[0], extents[1]))
+
     print etree.tostring(svg)
 
 if __name__ == '__main__':

inkstitch/stitch_plan/stitch_plan.py

@@ -97,15 +97,26 @@ class StitchPlan(object):
         return sum(block.num_stitches for block in self)
 
     @property
-    def dimensions(self):
+    def bounding_box(self):
         color_block_bounding_boxes = [cb.bounding_box for cb in self]
         minx = min(bb[0] for bb in color_block_bounding_boxes)
         miny = min(bb[1] for bb in color_block_bounding_boxes)
         maxx = max(bb[2] for bb in color_block_bounding_boxes)
         maxy = max(bb[3] for bb in color_block_bounding_boxes)
 
+        return minx, miny, maxx, maxy
+
+    @property
+    def dimensions(self):
+        minx, miny, maxx, maxy = self.bounding_box
         return (maxx - minx, maxy - miny)
 
+    @property
+    def extents(self):
+        minx, miny, maxx, maxy = self.bounding_box
+
+        return max(-minx, maxx), max(-miny, maxy)
+
     @property
     def dimensions_mm(self):
         dimensions = self.dimensions