Fix arcpoly conversion bugs

tests/test_primitives.py

@@ -47,8 +47,25 @@ def object_test(tmpfile, img_support, epsilon=1e-4):
 
     out_svg = tmpfile('SVG Output', '.svg')
     with open(out_svg, 'w') as f:
+        # Use inch units here to make sure we and gerbv agree on the exact pixel size of the output since both calculate
+        # it from the DPI setting.
         f.write(str(gbr.to_svg(force_bounds=bounds, arg_unit='inch', fg='black', bg='white')))
 
+    # test primitive to_arc_poly
+    arc_poly_gbr = GerberFile()
+    for obj in gbr.objects:
+        for primitive in obj.to_primitives(MM):
+            poly = primitive.to_arc_poly()
+            arc_poly_gbr.objects.append(Region.from_arc_poly(poly))
+
+    arc_poly_svg = tmpfile('ArcPoly SVG Output', '.svg')
+    with open(arc_poly_svg, 'w') as f:
+        f.write(str(arc_poly_gbr.to_svg(force_bounds=bounds, arg_unit='inch', fg='black', bg='white')))
+
+    arc_poly_png = tmpfile('ArcPoly conversion render', '.png')
+    img_support.svg_to_png(arc_poly_svg, arc_poly_png, dpi=300, bg='white')
+
+    # Reference export via gerber through GerbV
     out_gbr = tmpfile('GBR Output', '.gbr')
     gbr.save(out_gbr)
 
@@ -70,6 +87,11 @@ def object_test(tmpfile, img_support, epsilon=1e-4):
     assert mean < epsilon
     assert hist[3:].sum() < epsilon*hist.size
 
+    mean, _max, hist = img_support.image_difference(out_png, arc_poly_png, diff_out=tmpfile('ArcPoly Difference', '.png'))
+    assert hist[9] < 1
+    assert mean < epsilon
+    assert hist[3:].sum() < epsilon*hist.size
+
 @pytest.mark.parametrize('angle_deg', [0, 5, -5, 10, -10, 15, -15, 30, -30, 45, -45, 60, -60, 75, -75, 90, -90, 120, -120, 180, 153, 155, 157])
 def test_line(angle_deg, tmpfile, img_support):
     with object_test(tmpfile, img_support) as gbr: