render_gds.py

Renders a GDS to SVG, coloured with the layer map from cic/sky130A.tech. Run by make lplot:

python3 ../tech/magic/render_gds.py gds/<CELL>.gds lplot/<CELL>.svg [tech.json]

The tech file is optional; without it the script looks for ../cic/sky130A.tech relative to its own location.

Why gdstk and not KLayout

The output has to be a real vector SVG so it scales without loss when it is embedded in the documentation PDF. KLayout’s Python API has no SVG export, so gdstk does the writing.

What it does with the tech file

For every layer with a number, a datatype and a color, it builds an SVG style keyed on the (number, datatype) pair. The first definition wins, which matters because several ciccreator layer names share one GDS purpose.

fill: nofill in the tech file becomes an outline: no fill, 1 px stroke.
Anything else becomes a translucent fill at 55% opacity with a 0.5 px stroke, so overlapping layers stay readable.
Colour names are resolved through a small table (red, goldenrod, aqua, …); an unknown name falls back to grey, and a #rrggbb value is used as is.

Layers (235, 0), (235, 4) and (235, 5), the prBoundary and area-ID layers, are filtered out of every cell before rendering. They are usually the largest shapes in the file, and leaving them in would inflate the SVG viewBox so the actual layout is drawn small.

The top cell is written at scaling=20 with a 2% pad on a white background. Requires gdstk; the script has no other dependency.