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Programmable Scalable Vector Graphics -- drawings that draw themselves

Project README

PSVG - Programmable SVG

Doc | Playground | Examples | NPM

PSVG is an extension of the SVG (Scalable Vector Graphics) format that introduces programming language features like functions, control flows, and variables -- Instead of writing a program that draws a picture, write a picture that draws itself!

PSVG is compliant with XML and HTML specs, so it can be easily embedded in a webpage or edited with an XML editor.

This repo contains a PSVG→SVG complier that transforms PSVG files to just regular SVG's. It can also automatically render all PSVG's on an HTML page when included as a <script>.

Note: Experimental and under development, currently the compiler is not very friendly and might misbehave at times; Contributions/Issues welcome.

For example, define a recursive function that draws the Sierpiński's triangle:

<psvg width="300" height="260">

  <def-sierptri x1="{WIDTH/2}" y1="0" x2="{WIDTH}" y2="{HEIGHT}" x3="0" y3="{HEIGHT}" d="7">
    <path d="M{x1} {y1} L{x2} {y2} L{x3} {y3} z"/>
    <if false="{d}">
      <return/>
    </if>
    <sierptri x1="{x1}" y1="{y1}" x2="{(x1+x2)/2}" y2="{(y1+y2)/2}" x3="{(x3+x1)/2}" y3="{(y3+y1)/2}" d="{d-1}"/>
    <sierptri x1="{x2}" y1="{y2}" x2="{(x2+x3)/2}" y2="{(y2+y3)/2}" x3="{(x1+x2)/2}" y3="{(y1+y2)/2}" d="{d-1}"/>
    <sierptri x1="{x3}" y1="{y3}" x2="{(x3+x1)/2}" y2="{(y3+y1)/2}" x3="{(x2+x3)/2}" y3="{(y2+y3)/2}" d="{d-1}"/>
  </def-sierptri>

  <fill opacity="0.1"/>
  <sierptri/>

</psvg>

Which looks like this (after running it through the PSVG to SVG complier):

Since PSVG is a superset of SVG, all the elements in SVG are also in PSVG, and all of them are programmable. For example, you can use a for loop to generate a bunch of gradients whose stops are determined by a function of the index.

<var n="12"/>

<defs>
  <for i="0" true="{i<n}" step="1">
    <var t="{i/(n-1)}"/>
    <linearGradient id="grad{i}">
      <stop offset="0%"   stop-color="black"/>
      <stop offset="100%" stop-color="rgb(200,{FLOOR(LERP(0,255,t))},0)"/>
    </linearGradient>
  </for>
</defs>

Which will generate gradients with ids grad0, grad1, grad2, ... To use, simply write:

<rect fill="url(#grad7)"/>

The above is a simplified excerpt from examples/pythagoras.psvg, which utilizes this "gradient of gradient" to colorize a tree:

To transform shapes in vanilla SVG, the "group" metaphor (<g transform="...">) is often used. In addition to groups, PSVG also introduces Processing/p5.js-like pushMatrix() popMatrix() metaphors. For example, from the same examples/pythagoras.psvg as above, the <push></push> tag combined with <translate/> <roatate/> are used to draw a fractal tree:

<def-pythtree w="" d="{depth}">
  <push>
    <fill color="url(#grad{depth-d})"/>
    <path d="M0 {w/2} L{w/2} 0 L{w/2} {-w} L{-w/2} {-w} L{-w/2} 0 z"/>
  </push>

  <if true="{d==0}">
    <return/>
  </if>
  <push>
    <translate x="{-w/4}" y="{-w-w/4}"/>
    <rotate deg="-45"/>
    <pythtree w="{w/SQRT(2)}" d="{d-1}"/>
  </push>
  <push>
    <translate x="{w/4}" y="{-w-w/4}"/>
    <rotate deg="45"/>
    <pythtree w="{w/SQRT(2)}" d="{d-1}"/>
  </push>
</def-pythtree>

You can have your own pick of degree or radians: <rotate deg="45"> or <rotate rad="{PI/4}"/> are the same. You can also use <scale x="2" y="2"/> to scale subsequent drawings.

Similarly, styling can also be written as commands to effect subsequent draw calls:

<stroke color="red" cap="round"/>
<fill color="green"/>

<path d="...">
<polyline points="...">

In addition to simple fractals shown above, PSVG is also capable of implementing complex algorithms, as it's a full programming language. For example, an implementation of Poisson disk sampling described in this paper, examples/poisson.psvg:

The PSVG to SVG Compiler

A baseline PSVG to SVG complier is included in this repo. It is a very "quick-and-dirty" implementation that eval()s transpiled JavaScript. So for now, don't compile files you don't trust!

As command-line tool

Install it globally via npm

npm i -g @lingdong/psvg

and use it with:

psvg input.svg > output.svg

For example, to compile the hilbert curve example in this repo:

psvg examples/hilbert.psvg > examples/hibert.svg

or try it without installing via npx (comes together with npm)

npx -s @lingdong/psvg input.svg > output.svg

For the browser

PSVG is also available for browser via CDN, or directly download

<script src="http://unpkg.com/@lingdong/psvg"></script>

By including the script, all the <psvg> elements on the webpage will be compiled to <svg> when the page loads. Again, don't include PSVG files that you don't trust.

As a library

Install locally in your project via npm

npm i @lingdong/psvg
import { compilePSVG } from "@lingdong/psvg"

console.log(compilePSVG("<psvg>...</psvg>"))

or

const { compilePSVG } = require("@lingdong/psvg")

console.log(compilePSVG("<psvg>...</psvg>"))

Additionally, parsePSVG() transpilePSVG() and evalPSVG() which are individual steps of compilation are also exported.

In browsers, functions are exported under the global variable PSVG.

Check out QUICKSTART.md for a quick introduction to the PSVG language.

Editor Support

Syntax highlighting and auto-completion can be configured for editors by:

VS Code

Add the following lines to your settting.json. details

  "files.associations": {
    "*.psvg": "xml"
  }

GitHub

To get highlighting for PSVG files in your repositories on GitHub, create .gitattributes file at the root of your repo with the following content. details

*.psvg linguist-language=SVG

Other editors

Since PSVG is compliant with XML and HTML specs, you can always alias your language id to XML or SVG via the corresponding config on your editor.

Open Source Agenda is not affiliated with "Psvg" Project. README Source: LingDong-/psvg
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