@thi.ng/hiccup-svg

This project is part of the @thi.ng/umbrella monorepo.

About

SVG element functions & conversion for @thi.ng/hiccup & @thi.ng/hdom.

Important

The functions provided here do produce valid hiccup elements, but since none of them make use of (or support) the global hiccup / hdom context object, they can ONLY be invoked directly, i.e. they MUST be called like:

// correct (direct invocation)
svg.svg({}, svg.circle([0, 0], 100, { fill: "red" }));
 
// incorrect / unsupported (lazy evaluation)
[svg.svg, {}, [svg.circle, [0, 0], 100, { fill: "red" }]]

SVG conversion of @thi.ng/geom & @thi.ng/hdom-canvas shape trees

Since v2.0.0 this package provides a conversion utility to translate the more compact syntax used by @thi.ng/geom and @thi.ng/hdom-canvas shape trees (designed for more performant realtime / canvas drawing) into a SVG serializable hiccup format.

The convertTree() function takes a pre-normalized hiccup tree of hdom-canvas shape definitions and recursively converts it into an hiccup flavor which is ready for SVG serialization (i.e. using stringified geometry attribs). This conversion also involves translation & re-organization of various attributes, as described below. This function returns a new tree. The original remains untouched, as will any unrecognized tree / shape nodes (those will be transferred as-is to the result tree). See example below.

Automatic attribute conversions

Colors

Since v3.1.0:

Color conversions are only applied to fill and stroke attributes and color stops provided to linearGradient(), radialGradient()

String

String color attribs prefixed with $ are replaced with url(#...) refs (e.g. to refer to gradients), else used as is (untransformed)

Number

Interpreted as ARGB hex value:

{ fill: 0xffaabbcc } => { fill: "#aabbcc" }

Array

Interpreted as float RGB(A):

{ fill: [1, 0.8, 0.6, 0.4] } => { fill: "rgba(255,204,153,0.40)" }

@thi.ng/color values

Converted to CSS color strings:

{ fill: hcya(0.1666, 1, 0.8859) } => { fill: "#ffff00" }

Transforms

(i.e. transform, rotate, scale, translate)

If an element has a transform attrib, conversion of the other transformation attribs will be skipped, else the values are assumed to be either strings or:

• transform: 6-element numeric array (2x3 matrix in column major order)
• translate: 2-element array
• rotate: number (angle in radians)
• scale: number (uniform scale) or 2-elem array

If no transform, but others are given, the resulting transformation order will always be TRS. Any string values will be used as-is and therefore need to be complete, e.g. { rotate: "rotate(60)" }

Installation

yarn add @thi.ng/hiccup-svg

Dependencies

• @thi.ng/checks
• @thi.ng/color
• @thi.ng/hiccup

Usage examples

import * as svg from "@thi.ng/hiccup-svg";
import { serialize } from "@thi.ng/hiccup";
import * as fs from "fs";
 
fs.writeFileSync(
    "hello.svg",
    serialize(
        svg.svg(
            {width: 100, height: 100},
            svg.defs(svg.linearGradient("grad", [0, 0], [0, 1], [[0, "red"], [1, "blue"]])),
            svg.circle([50, 50], 50, { fill: "url(#grad)" }),
            svg.text([50, 55], "Hello", { fill: "white", "text-anchor": "middle" })
        )
    ));

Minimal example showing SVG conversion of a hdom-canvas scene:

// scene tree defined for hdom-canvas
const scene = [
    ["defs", {},
        ["radialGradient",
            { id: "bg", from: [150, 280], to: [150, 300], r1: 300, r2: 100 },
            [[0, "#07f"], [0.5, "#0ef"], [0.8, "#efe"], [1, "#af0"]]],
        ["radialGradient",
            { id: "sun", from: [110, 120], to: [110, 120], r1: 5, r2: 50 },
            [[0, "#fff"], [1, "rgba(255,255,192,0)"]]]
    ],
    ["circle", { fill: "$bg" }, [150, 150], 130],
    ["circle", { fill: "$sun" }, [110, 120], 50],
];
 
fs.writeFileSync(
    "radialgradient.svg",
    serialize(
        svg.svg({ width: 300, height: 300 }, svg.convertTree(scene))
    )
);

Result:

<svg version="1.1"
    xmlns="http://www.w3.org/2000/svg" 
    xmlns:xlink="http://www.w3.org/1999/xlink" width="300" height="300">
    <defs>
        <radialGradient id="bg" fx="150.00" fy="280.00" cx="150.00" cy="300.00" fr="300.00" r="100.00" gradientUnits="userSpaceOnUse">
            <stop offset="0" stop-color="#07f"/>
            <stop offset="0.5" stop-color="#0ef"/>
            <stop offset="0.8" stop-color="#efe"/>
            <stop offset="1" stop-color="#af0"/>
        </radialGradient>
        <radialGradient id="sun" fx="110.00" fy="120.00" cx="110.00" cy="120.00" fr="5.00" r="50.00" gradientUnits="userSpaceOnUse">
            <stop offset="0" stop-color="#fff"/>
            <stop offset="1" stop-color="rgb(255,255,192)" stop-opacity="0"/>
        </radialGradient>
    </defs>
    <circle cx="150.00" cy="150.00" r="130.00" fill="url(#bg)"/>
    <circle cx="110.00" cy="120.00" r="50.00" fill="url(#sun)"/>
</svg>

Authors

• Karsten Schmidt

License

© 2016 - 2018 Karsten Schmidt // Apache Software License 2.0