How to read polygons from GDS into numpy arrays?

bertwa

Hi, I'm a beginner using klayout.db in python. How would I read polygons from a GDS into numpy arrays using klayout.db?

sekigawa

Hi @bertwa,

Just for your info.

Playing with ChatGPT

<ChatGPT 4o Prompt>
Using the KLayout Python module installed by 'python3 -m pip install klayout', I want to:
1. Read a GDS2/OASIS file
2. Iterate over all layers and polygons (including boxes)
3. Store the vertices of each polygon in a numpy array
4. Each numpy array needs to be stored in a dictionary, where the key is (layer, datatype, polygon_number)
5. Finally, dump the dictionary. If the vertex list is long, truncate it appropriately.
Suggest a sample code.

The suggested code is not perfect in the beginning, as shown below, but it's a good starting point.

MacBookPro2{sekigawa} Forum2694 (1)% ./f2694.py
Traceback (most recent call last):
  File "/Users/sekigawa/GitWork/ForumKLayout/Forum/Forum2694/./f2694.py", line 41, in <module>
    for layer_index in range(layout.layer_indices()):
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'list' object cannot be interpreted as an integer

Debugged Code

import klayout.db as db
import numpy as np

# === Parameters ===
filename = "inv2.gds"  # Replace with your actual GDS/OASIS file
truncate_vertices = 10      # Max number of vertices to show when dumping

# === Load layout ===
layout = db.Layout()
layout.read(filename)

# === Dictionary to store polygons ===
polygon_dict = {}

# === Iterate through all cells and shapes ===
for cell in layout.each_cell():
    for layer_index in layout.layer_indices():
        layer_info = layout.get_info(layer_index)
        layer_shapes = cell.shapes(layer_index)

        polygon_number = 0
        for shape in layer_shapes.each():
            if shape.is_box():
                # Convert box to DPolygon
                dbox = db.DBox(shape.box)
                poly = db.DPolygon(dbox)
            elif shape.is_polygon():
                poly = db.DPolygon(shape.polygon)
            else:
                continue  # Skip non-polygonal shapes (e.g., paths, texts)

            # Extract vertices as a numpy array
            points = np.array([[pt.x, pt.y] for pt in poly.each_point_hull()])
            key = (layer_info.layer, layer_info.datatype, polygon_number)
            polygon_dict[key] = points
            polygon_number += 1

# === Dump dictionary ===
print(f"### Total number of Polygons/Boxes in {filename} = {len(polygon_dict)} ###")
for key, vertices in polygon_dict.items():
    v_short = vertices if len(vertices) <= truncate_vertices else vertices[:truncate_vertices]
    print(f"{key}: {v_short.tolist()} {'... (truncated)' if len(vertices) > truncate_vertices else ''}")

Sample Run

MacBookPro2{sekigawa} Forum2694 (2)% ./f2694.py
### Total number of Polygons/Boxes in inv2.gds = 47 ###
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

(1, 0, 0): [[0.0, 2950.0], [0.0, 6150.0], [3000.0, 6150.0], [3000.0, 2950.0]]
(2, 0, 0): [[450.0, 4200.0], [450.0, 5700.0], [1600.0, 5700.0], [1600.0, 4200.0]]
(2, 0, 1): [[1950.0, 200.0], [1950.0, 1400.0], [2550.0, 1400.0], [2550.0, 200.0]]
:
:
(8, 0, 7): [[2150.0, 5550.0], [2150.0, 5750.0], [2350.0, 5750.0], [2350.0, 5550.0]]
(9, 0, 0): [[0.0, 0.0], [0.0, 1000.0], [3000.0, 1000.0], [3000.0, 0.0]]
(9, 0, 1): [[0.0, 4900.0], [0.0, 5900.0], [3000.0, 5900.0], [3000.0, 4900.0]]