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authorjaseg <git@jaseg.de>2023-09-22 18:50:58 +0200
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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')