chalk-diagrams 0.2.1

A declarative drawing API

Chalk is a declarative drawing library built on top of PyCairo. The API draws heavy inspiration from Haskell's diagrams, Scala's doodle and Jeremy Gibbons's lecture notes on Functional Programming for Domain−Specific Languages.

The documentation is available at https://chalk-diagrams.github.io.

⚠️ The library is still very much work in progress and subject to change.

Installation

The library is available on PyPI as chalk-diagrams and can be installed with pip:

pip install git+https://github.com/chalk-diagrams/chalk/

On Debian (or Colab) you will need to install Cairo

sudo apt-get install libcairo2-dev

If you want to use the LaTeX extension, run:

pip install chalk-diagrams[latex]

For the LaTeX extension you might need to install pdf2svg and texlive; on Debian these dependencies can be installed as follows:

sudo apt-get install pdf2svg texlive texlive-science texlive-latex-recommended texlive-latex-extra

Installation with Conda

You can install the library with conda from conda-forge channel.

conda install -c conda-forge chalk-diagrams

Overview

Below we provide a brief introduction of the main functionality of the library. These examples are available in the examples/intro.py file.

We start by importing the colour module and the diagrams functions:

from colour import Color
from chalk import *

We also define some colors that will be shortly used:

papaya = Color("#ff9700")
blue = Color("#005FDB")

We can easily create basic shapes (the functions circle, square, triangle) and style them with various attributes (the methodsfill_color, line_color, line_width). For example:

d = circle(1).fill_color(papaya)

The diagram can be saved to an image using the render method:

d.render("examples/output/intro-01.png", height=64)

We can glue together two diagrams using the combinators atop (or +), beside (or |), above (or /). For example:

circle(0.5).fill_color(papaya) | square(1).fill_color(blue)

which is equivalent to

circle(0.5).fill_color(papaya).beside(square(1).fill_color(blue))

This code produces the following image:

We also provide combinators for a list of diagrams: hcat for horizontal composition, vcat for vertical composition. For example:

hcat(circle(0.1 * i) for i in range(1, 6)).fill_color(blue)

We can use Python functions to build more intricate diagrams:

def sierpinski(n: int, size: int) -> Diagram:
    if n <= 1:
        return triangle(size)
    else:
        smaller = sierpinski(n - 1, size / 2)
        return smaller.above(smaller.beside(smaller).center_xy())

d = sierpinski(5, 4).fill_color(papaya)

Gallery of examples

For more examples, please check the examples folder; their output is illustrated below:

squares.py	logo.py	escher_square.py
hilbert.py	koch.py	hex-variation.py
lenet.py	tensor.py	hanoi.py
tree.py	lattice.py

These scripts can be run as follows:

python examples/squares.py

Authors

• Dan Oneață
• Alexander Rush

Special thanks to:

• Sugato Ray, for his significant contributions and suggestions;
• Ionuț G. Stan, for providing many useful insights and comments.