WiP

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+.. _examples-doc:
+
+Examples
+========
+
+Solder mask rings
+-----------------
+
+This example script takes a board exported with a more recent KiCad version, and removes solder mask everywhere, but
+leaves a thin ring of solder mask around every pad. Might be useful for some artsy boards.
+
+.. image:: ex-mask-islands.png
+
+.. code-block:: python
+    from gerbonara import *
+    from shapely import *
+
+    stack = layers.LayerStack.open('gerber')
+    # Let's work in mm here. Gerbonara will take care to convert units when the file is in US customary units.
+    (x1, y1), (x2, y2) = stack.bounding_box(unit=utils.MM)
+
+    for l in [stack['bottom mask'], stack['top mask']]:
+
+        # The solder mask gerber layer by convention is "negative". That is, a "dark" polarity (drawn) Gerber primitive
+        # will result in an opening in the solder mask. Conversely, an empty gerber file would lead to the entire board
+        # being covered in solder mask.
+        #
+        # Here, we add a rectangle covering the entire board so the entire board is *free* of solder mask.
+
+        new = [graphic_objects.Region(
+            [(x1, y1), (x1, y2), (x2, y2), (x2, y1), (x1, y1)],
+            unit=utils.MM,
+            polarity_dark=True)]
+
+        # Iterate through all objects on the solder mask layer. In later KiCad versions, everything on the solder mask
+        # layer is exported as a Gerber region, which is a really bad idea, but makes things easy for us here.
+        for obj in l.objects:
+            if isinstance(obj, gerbonara.graphic_objects.Region):
+                regions = []
+            else:
+                regions = [gerbonara.graphic_objects.Region.from_arc_poly(prim.to_arc_poly())
+                    for prim in obj.to_primitives(unit=gerbonara.utils.MM)]
+
+            for obj in regions:
+                # Convert the region to a shapely line string
+                ls = LineString(obj.outline).normalize()
+
+                # Ask shapely to offset the line string by 1 mm
+                out = ls.offset_curve(obj.unit(1, 'mm'))
+
+                # For negative offsets, this operation can result in an object being split up into multiple parts, so we
+                # might get back a MultiLineString instead of a LineString.
+                for ls in (out.geoms if hasattr(out, 'geoms') else [out]):
+
+                    # Convert the resulting shapely object back to a Gerber region.
+                    new.append(graphic_objects.Region(
+                        unit=obj.unit,
+                        polarity_dark=not obj.polarity_dark,
+                        outline=list(ls.coords)))
+
+        # Append the new objects to the original layer data
+        l.objects = new + l.objects
+    # Write the modified layer stack to a new Gerber directory
+    stack.save_to_directory('output-gerbers')