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+---
+description: Generating geometric line art
+created: 2024-05-12
+---
+
+![Envelope](Envelope.png)
+
+Needed a clean picture of [Envelope (mathematics)](https://en.wikipedia.org/wiki/Envelope_%28mathematics%29), 
+for PCB silk screen art.
+I used [Python Pillow](https://python-pillow.org/)
+```sh
+pip install pillow~=10.3
+```
+
+```python
+from PIL import Image, ImageDraw
+
+# https://en.wikipedia.org/wiki/Envelope_%28mathematics%29
+
+dim = 200  # Image dimensions (pixels)
+skip = 10   # Only draw a line every X pixels
+width = 1   # Line width
+color = "white"
+
+with Image.new(mode = "RGB", size = (dim, dim)) as im:  # mode="RGBA" for transparent background
+    draw = ImageDraw.Draw(im)
+
+    for i in range(dim):
+        if i % skip:
+            continue
+        rev = dim - i
+        draw.line([(0, i), (i, dim)], fill=color, width=width) 
+    
+    im.show()  # im.save("/tmp/Envelope.png")
+```