plottool

A tool for sending HPGL files to a plotter or cutting plotter connected over a serial port. Includes path optimization, blade offset compensation, scaling, rotation, tiling, weeding lines, config profiles, and a graphical preview window.

Tested with a Cogi CT-630 cutting plotter @ Stratum0: https://stratum0.org/wiki/Cogi_CT-630

Also works on macOS, but less reliably — prepare for occasional job cancellation.

Forked from stratum0/plottool.

This project is being actively extended with the help of Claude Code (Anthropic AI).

Dependencies

For Debian-based Linux distributions (Ubuntu, Mint):

sudo apt-get install python3-serial python3-wxgtk4.0 python3-numpy

For Arch Linux:

sudo pacman -S python-numpy python-pyserial python-wxpython

For macOS (homebrew + pip):

pip install numpy pyserial && brew install wxpython

Or install via pip from the repository root:

pip install .

Usage — plottool.py

Send an HPGL file to the plotter:

./plottool.py file.hpgl
./plottool.py file.hpgl -m --width 200
./plottool.py file.hpgl --profile vinyl

Options:

On macOS, serial devices follow a different naming convention — look for something like /dev/tty.usbserial-14430 or /dev/cu.usbserial-14430.

Usage — hpgl.py

Process an HPGL file without plotting (convert, optimise, preview, export):

./hpgl.py file.hpgl -o out.hpgl -p preview.svg
./hpgl.py file.hpgl -m --rotate 90 -o out.hpgl

Supports all flags from plottool.py except --port, --baud, and --preview (which is -p SVG here, exporting to an SVG file instead of opening a window).

Processing pipeline

When multiple options are active, they are applied in this order:

1. Scale (--width / --height / --scale)
2. Rotate (--rotate)
3. Mirror (--mirror) — flip left-right
4. Flip (--flip) — flip top-bottom
5. Optimize (--magic) — remove redundant points, fit to origin
6. Blade offset (--magic) — overshoot correction at corners
7. Tile (--repeat-x / --repeat-y)
8. Weeding lines (--weed)
9. Reroute (--reroute) — reorder paths for travel efficiency
10. Blade prep cut — 2 mm seating cut prepended at origin (disable with --no-blade-prep)

Weeding lines

Add cut lines to help remove waste vinyl after cutting. Select a strategy with --weed STRATEGY:

Line density is controlled by --weed-size PCT (max waste piece size as % of bbox area, default 25). All strategies support adaptive clipping (default on): weeding lines are split at design intersections so only waste-area segments are kept. An outer frame rectangle (1 mm from bbox by default) is added automatically.

See WEEDING_LINES.md for full parameter details.

Config file

Settings can be stored in ~/.plottoolrc (global) or plottool.conf in the current directory (local, takes precedence). The format is INI:

[default]
magic = true
blade-offset = 0.3

[vinyl]
width = 300
reroute = nearest

[shirt]
mirror = true
width = 300

[pen]
pen = true
no-blade-prep = true

The [default] section always applies. Use --profile NAME to also apply a named section on top. Command-line arguments always override config values. See plottool.conf.example for a full annotated example.

Preview window

The preview window (-v in plottool.py, -p SVG exports to file in hpgl.py) shows the processed paths with:

• Direction arrows on cut paths, travel moves, and the return-to-origin line
• Dotted travel (pen-up) lines
• Start-of-cut (filled blue dot) and end-of-cut (blue ring) markers at every pen transition
• The design bounding box before weeding lines are added (green rectangle)

Interactive controls (plottool.py preview window):