Node-GCanvas is GCanvas(OpenGLES) backed Canvas implementation for Node.js. It provide a way use GCanvas in Node.js environment. So you can use canvas-like object to do your own render task at server side just like on Web. Now, we just support Linux.

Installation

npm install @gcanvas/node

Note: Node.js version >=10.0。

Compiling

Since GCanvas relies on OpenGL for graphics rendering, you need to install the dependency libraries needed for OpenGL operation on the corresponding system. Meanwhile, the GCanvas is built with CMake, so the system needs to install the CMake version >=3.8.0. The dependency libraries required to install the GCanvas run on each operating system are listed below.

OS	Command
OS X	Not support
Ubuntu 18.04	`sudo apt-get update && apt-get install -y libglfw3-dev libgles2-mesa-dev libboost-all-dev libfreetype6-dev libcurl4-openssl-dev libjpeg-dev` && install freetype字体库 && install cmake
Windows	Not support
Docker	Dockerfile

Quick Start Example

const { createCanvas, Image } = require('bindings')('canvas');
const canvas = createCanvas(400, 400);
const ctx = canvas.getContext('2d')

ctx.fillRect(0, 0, 150, 150) // Draw a rectangle with default settings
ctx.save() // Save the default state

ctx.fillStyle = '#09F' // Make changes to the settings
ctx.fillRect(15, 15, 120, 120) // Draw a rectangle with new settings

ctx.save() // Save the current state
ctx.fillStyle = '#FFF' // Make changes to the settings
ctx.globalAlpha = 0.5
ctx.fillRect(30, 30, 90, 90) // Draw a rectangle with new settings

ctx.restore() // Restore previous state
ctx.fillRect(45, 45, 60, 60) // Draw a rectangle with restored settings

ctx.restore() // Restore original state
ctx.fillRect(60, 60, 30, 30) // Draw a rectangle with restored settings

canvas.createPNG("demo1")

API Documentation

Standard APIs

GCanvas benchmarking Web Canvas API implementation, as close as possible to the Web Canvas API. The API documentation, please visit the [Mozilla Web Canvas API] (https://developer.mozilla.org/zh-CN/docs/Web/API/CanvasRenderingContext2D). (see this link for current API compatibility)
Standard API Supported
- function
  - getContext()
  - fillRect()
  - arc()
  - arcTo()
  - beginPath()
  - bezierCurveTo()
  - quadraticCurveTo()
  - clearRect()
  - clip()
  - closePath()
  - createImageData()
  - createLinearGradient()
  - createPattern()
  - createRadialGradient()
  - drawImage()
  - ellipse:not support
  - fill()
  - fillText()
  - getImageData()
  - getLineDash()
  - lineTo()
  - measureText()
  - moveTo()
  - putImageData()
  - rect()
  - resetTransform()
  - restore()
  - rotate()
  - save()
  - scale()
  - setLineDash()
  - setTransform()
  - stroke()
  - strokeRect()
  - strokeText()
  - transform()
  - translate()
- propetry
  - width
  - height
  - fillStyle
  - font
  - globalAlpha
  - globalCompositeOperation
  - lineCap
  - lineDashOffset
  - lineJoin
  - lineWidth
  - miterLimit
  - shadowBlur
  - shadowColor
  - shadowOffsetX
  - shadowOffsetY
  - strokeStyle
  - textAlign
  - textBaseline

Non-Standard APIs

createCanvas

createCanvas(width: number, height: number) => Canvas

let canvas = createCanvas(400, 400);

Image

img.src: string
img.onload:Function
img.onerror:Function

const img = new Image()
img.onload = () => {
	ctx.drawImage(img, 0, 0);
	canvas.createPNG("demo2");
}
img.onerror = err => {
	console.log(err)
}
img.src = 'https://alibaba.github.io/GCanvas/assets/logo-gcanvas.png'

const fs = require('fs')
const path = require('path')
const { createCanvas, Image } = require('bindings')('canvas');
const img = new Image()
const canvas = createCanvas(500, 500)
const ctx = canvas.getContext('2d')
	
img.onload = () => {
	ctx.drawImage(img, 0, 0)
	canvas.createPNG("local")
}
img.onerror = err => {
	throw err
}
	
img.src = path.join(__dirname,'images', 'image.png')

createPNG

createPNG(name:string) => void

let canvas = createCanvas(400, 400);
var ctx = canvas.getContext('2d');
ctx.fillStyle="#ff0000"
ctx.fillRect(0, 0, 150, 150) 
canvas.createPNG("demo1") //export a png picture

createJPEG

createPNG(name:string) => void

const { createCanvas, Image } = require('bindings')('canvas');
const canvas = createCanvas(400, 400);
const ctx = canvas.getContext('2d')
ctx.fillStyle = '#09F' 
ctx.fillRect(0, 0, 150, 150) // Draw a rectangle with default settings
canvas.createJPEG("demo2") // export a jpeg picture

createPNGStream

createPNGStream(void) => void

const { createCanvas, Image } = require('../export')
const canvas = createCanvas(400, 400);
const ctx = canvas.getContext('2d')
const fs = require('fs')
const path = require('path');
const out = fs.createWriteStream(path.join(__dirname, "..")+ '/demo1.png');
ctx.fillStyle = '#09F' 
ctx.fillRect(0, 0, 150, 150) // Draw a rectangle with default settings
var stream = canvas.createPNGStream();
    stream.on('data', function (chunk) {
    out.write(chunk);
});

createJPEGStream

createJPEGStream(void) => void

const { createCanvas, Image } = require('../export')
const canvas = createCanvas(400, 400);
const ctx = canvas.getContext('2d')
const fs = require('fs')
const path = require('path');
const out = fs.createWriteStream(path.join(__dirname, "..")+ '/demo1.jpg');
ctx.fillStyle = '#09F' 
ctx.fillRect(0, 0, 150, 150) // Draw a rectangle with default settings
var stream = canvas.createJPEGStream();
    stream.on('data', function (chunk) {
    out.write(chunk);
});

toBuffer

toBuffer(string?) => ArrayBuffer

const { createCanvas, Image } = require('../export')
const canvas = createCanvas(400, 400);
const ctx = canvas.getContext('2d')
const fs = require('fs')
const path = require('path');
ctx.fillStyle="#ff0000"
ctx.fillRect(0, 0, 150, 150) //

fs.writeFile(`${path.join(__dirname, "..")}/tobuffer.png`, canvas.toBuffer("image/png"), err => {
    if (err) {
        throw err;
    }
});

fs.writeFile(`${path.join(__dirname, "..")}/tobuffer.jpg`, canvas.toBuffer("image/jpeg"), err => {
    if (err) {
        throw err;
    }
});

var buffer=canvas.toBuffer("raw")
console.log(buffer)

Node-GCanvas Source Code Build & Test Running

If you want to build and develop based on source code, this document will show you how to build and run and test based on source code.

Node-canvas USES node-addon's binding API and builds with cmake-js.

Step of build

npm install cmake-js -g //install cmake-js
local=true npm install // install dependency ,local=true means install with source
cmake-js compile // build project

Step of running

case=app.js npm run test //run *.js of example folder，output the runing result like png picture
case=app.js npm run test-headless// if you don't have system display,you can use this command

Examples

Examples line in the examples/ directory. Most produce a png image of the same name.

README.MD Unescape Escape

Node-GCanvas