Allow negative render of soldermask per #50

Update example code and rendering to show change

1 files changed, 18 insertions, 3 deletions

diff --git a/gerber/render/render.py b/gerber/render/render.py
index 8f49796..737061e 100644
--- a/gerber/render/render.py
+++ b/gerber/render/render.py
@@ -23,12 +23,13 @@ Rendering
 Render Gerber and Excellon files to a variety of formats. The render module
 currently supports SVG rendering using the `svgwrite` library.
 """
+
+
+from ..primitives import *
 from ..gerber_statements import (CommentStmt, UnknownStmt, EofStmt, ParamStmt,
                                  CoordStmt, ApertureStmt, RegionModeStmt,
-                                 QuadrantModeStmt,
-)
+                                 QuadrantModeStmt,)
 
-from ..primitives import *
 
 class GerberContext(object):
     """ Gerber rendering context base class
@@ -182,3 +183,17 @@ class GerberContext(object):
     def _render_test_record(self, primitive, color):
         pass
 
+
+class Renderable(object):
+    def __init__(self, color=None, alpha=None, invert=False):
+        self.color = color
+        self.alpha = alpha
+        self.invert = invert
+
+    def to_render(self):
+        """ Override this in subclass. Should return a list of Primitives or Renderables
+        """
+        raise NotImplementedError('to_render() must be implemented in subclass')
+
+    def apply_theme(self, theme):
+        raise NotImplementedError('apply_theme() must be implemented in subclass')