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canvg

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    canvg

JavaScript SVG parser and renderer on Canvas.


Version published
Weekly downloads
1.5M
increased by1.91%
Maintainers
2
Install size
2.67 MB
Created
Weekly downloads
 

Package description

What is canvg?

The canvg npm package is a versatile library that allows users to parse and render SVG (Scalable Vector Graphics) to a Canvas element in a browser or on the server-side using Node.js. It is particularly useful for converting SVGs into Canvas for manipulation, rendering, or exporting purposes.

What are canvg's main functionalities?

Rendering SVG to Canvas

This code sample demonstrates how to load an SVG file, render it onto a Canvas, and then save the Canvas output as a PNG file. This is useful for server-side generation of images from SVG files.

const canvg = require('canvg');
const Canvas = require('canvas');
const fs = require('fs');

const canvas = Canvas.createCanvas(800, 600);
const ctx = canvas.getContext('2d');
const svg = fs.readFileSync('path/to/your/svgfile.svg', 'utf-8');
canvg(ctx, svg);

const out = fs.createWriteStream('path/to/output.png');
const stream = canvas.createPNGStream();
stream.pipe(out);

Manipulating SVG before rendering

This example shows how to manipulate SVG data by changing its color before rendering it to a Canvas. This is useful for dynamically altering the appearance of SVGs based on runtime conditions.

const canvg = require('canvg');
const Canvas = require('canvas');
const fs = require('fs');

const canvas = Canvas.createCanvas(800, 600);
const ctx = canvas.getContext('2d');
let svg = fs.readFileSync('path/to/your/svgfile.svg', 'utf-8');

// Modify SVG data
svg = svg.replace('fill:#000000', 'fill:#123456');

// Render modified SVG to canvas
canvg(ctx, svg);

Other packages similar to canvg

Changelog

Source

[3.0.8] - 2021-07-31

Fixed

  • #1460
  • #108
  • #1439
  • #1364

Readme

Source

canvg

NPM version Dependencies status Build status Coverage status Dependabot badge Documentation badge

JavaScript SVG parser and renderer on Canvas. It takes the URL to the SVG file or the text of the SVG file, parses it in JavaScript and renders the result on Canvas.

Demo

Playground

Install

npm i canvg
# or
yarn add canvg

Usage

Basic module exports:

export default Canvg;
export {
    presets
};

Description of all exports you can find in Documentation.

Example

import Canvg from 'canvg';

let v = null;

window.onload = async () => {
    const canvas = document.querySelector('canvas');
    const ctx = canvas.getContext('2d');
    
    v = await Canvg.from(ctx, './svgs/1.svg');

    // Start SVG rendering with animations and mouse handling.
    v.start();
};

window.onbeforeunload = () => {
    v.stop();
};
OffscreenCanvas
import Canvg, {
    presets
} from 'canvg';

self.onmessage = async (event) => {
    const {
        width,
        height,
        svg
    } = event.data;
    const canvas = new OffscreenCanvas(width, height);
    const ctx = canvas.getContext('2d');
    const v = await Canvg.from(ctx, svg, presets.offscreen());

    // Render only first frame, ignoring animations and mouse.
    await v.render();

    const blob = await canvas.convertToBlob();
    const pngUrl = URL.createObjectURL(blob);

    self.postMessage({
        pngUrl
    });
};

OffscreenCanvas browsers compatibility.

NodeJS
import {
    promises as fs
} from 'fs';
import {
    DOMParser
} from 'xmldom';
import * as canvas from 'canvas';
import fetch from 'node-fetch';
import Canvg, {
    presets
} from 'canvg';

const preset = presets.node({
    DOMParser,
    canvas,
    fetch
});

(async (output, input) => {
    const svg = await fs.readFile(input, 'utf8');
    const canvas = preset.createCanvas(800, 600);
    const ctx = canvas.getContext('2d');
    const v = Canvg.fromString(ctx, svg, preset);

    // Render only first frame, ignoring animations.
    await v.render();

    const png = canvas.toBuffer();

    await fs.writeFile(output, png);

})(
    process.argv.pop(),
    process.argv.pop()
);
Resize
import Canvg, {
    presets
} from 'canvg';

self.onmessage = async (event) => {
    const {
        width,
        height,
        svg
    } = event.data;
    const canvas = new OffscreenCanvas(width, height);
    const ctx = canvas.getContext('2d');
    const v = await Canvg.from(ctx, svg, presets.offscreen());

    /**
     * Resize SVG to fit in given size.
     * @param width
     * @param height
     * @param preserveAspectRatio
     */
    v.resize(width, height, 'xMidYMid meet');

    // Render only first frame, ignoring animations and mouse.
    await v.render();

    const blob = await canvas.convertToBlob();
    const pngUrl = URL.createObjectURL(blob);

    self.postMessage({
        pngUrl
    });
};
Browser
<script type="text/javascript" src="https://unpkg.com/canvg@3.0.4/lib/umd.js"></script>
<script type="text/javascript">
window.onload = () => {
    const canvas = document.querySelector('canvas');
    const ctx = canvas.getContext('2d');
    
    v = canvg.Canvg.fromString(ctx, '<svg width="600" height="600"><text x="50" y="50">Hello World!</text></svg>');

    // Start SVG rendering with animations and mouse handling.
    v.start();

};
</script>
<canvas />

Options

The third parameter of new Canvg(...), Canvg.from(...) and Canvg.fromString(...) is options:

interface IOptions {
    /**
     * WHATWG-compatible `fetch` function.
     */
    fetch?: typeof fetch;
    /**
     * XML/HTML parser from string into DOM Document.
     */
    DOMParser?: typeof DOMParser;
    /**
     * Window object.
     */
    window?: Window;
    /**
     * Whether enable the redraw.
     */
    enableRedraw?: boolean;
    /**
     * Ignore mouse events.
     */
    ignoreMouse?: boolean;
    /**
     * Ignore animations.
     */
    ignoreAnimation?: boolean;
    /**
     * Does not try to resize canvas.
     */
    ignoreDimensions?: boolean;
    /**
     * Does not clear canvas.
     */
    ignoreClear?: boolean;
    /**
     * Scales horizontally to width.
     */
    scaleWidth?: number;
    /**
     * Scales vertically to height.
     */
    scaleHeight?: number;
    /**
     * Draws at a x offset.
     */
    offsetX?: number;
    /**
     * Draws at a y offset.
     */
    offsetY?: number;
    /**
     * Will call the function on every frame, if it returns true, will redraw.
     */
    forceRedraw?(): boolean;
    /**
     * Default `rem` size.
     */
    rootEmSize?: number;
    /**
     * Default `em` size.
     */
    emSize?: number;
    /**
     * Function to create new canvas.
     */
    createCanvas?: (width: number, height: number) => HTMLCanvasElement | OffscreenCanvas;
    /**
     * Function to create new image.
     */
    createImage?: (src: string, anonymousCrossOrigin?: boolean) => Promise<CanvasImageSource>;
    /**
     * Load images anonymously.
     */
    anonymousCrossOrigin?: boolean;
}
Options presets

There are two options presets:

What's implemented?

The end goal is everything from the SVG spec. The majority of the rendering and animation is working. If you would like to see a feature implemented, don't hesitate to add it to the issues list, or better is to create pull request 😎

Keywords

FAQs

Last updated on 14 Sep 2021

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