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Canvas

Introduction

Drawing on canvas.

  • Author: Rex
  • Game object

Live demos

Usage

Sample code

Install plugin

Load minify file

  • Load plugin (minify file) in preload stage 
    scene.load.plugin('rexcanvasplugin', 'https://raw.githubusercontent.com/rexrainbow/phaser3-rex-notes/master/dist/rexcanvasplugin.min.js', true);
  • Add canvas object 
    var canvas = scene.add.rexCanvas(x, y, width, height);

Import plugin

  • Install rex plugins from npm 
    npm i phaser3-rex-plugins
  • Install plugin in configuration of game 
    import CanvasPlugin from 'phaser3-rex-plugins/plugins/canvas-plugin.js';
var config = {
    // ...
    plugins: {
        global: [{
            key: 'rexCanvasPlugin',
            plugin: CanvasPlugin,
            start: true
        },
        // ...
        ]
    }
    // ...
};
var game = new Phaser.Game(config);
  • Add canvas object 
    var canvas = scene.add.rexCanvas(x, y, width, height);

Import class

  • Install rex plugins from npm 
    npm i phaser3-rex-plugins
  • Import class 
    import Canvas from 'phaser3-rex-plugins/plugins/canvas.js';
  • Add canvas object 
    var canvas = new Canvas(scene, x, y, width, height);
scene.add.existing(canvas);

Create instance

var canvas = scene.add.rexCanvas(x, y, width, height);
// var canvas = scene.add.rexCanvas(x, y, width, height, resolution);

Add canvas from JSON

var canvas = scene.make.rexCanvas({
    x: 0,
    y: 0,
    width: 256,
    height: 256,
    // resolution: 1,

    // origin: {x: 0.5, y: 0.5},
    // fill: null,

    add: true
});
  • resolution : The resolution the content is rendered to its internal canvas at. Default value is 1.

Custom class

  • Define class 
    class MyCanvas extends Canvas {
    constructor(scene, x, y, width, height, resolution) {
        super(scene, x, y, width, height, resolution);
        // ...
        scene.add.existing(this);
    }
    // ...

    // preUpdate(time, delta) {}
}
    • scene.add.existing(gameObject) : Adds an existing Game Object to this Scene.
      • If the Game Object renders, it will be added to the Display List.
      • If it has a preUpdate method, it will be added to the Update List.
  • Create instance 
    var canvas = new MyCanvas(scene, x, y, width, height, resolution);

Clear or fill canvas

  • Clear 
    canvas.clear();
  • Fill color 
    canvas.fill(color);

Update canvas

  1. Get canvas elemet 
    var canvasElem = canvas.getCanvas();
var context = canvas.getContext();
    or 
    var canvaesElem = canvas.canvas;
var context = canvas.context;
  2. Draw on context

Update display texture

  • Update texture when rendering 
    canvas.needRedraw();
    or 
    canvas.dirty = true;
  • Update texture now 
    canvas.updateTexture();
    or update canvas and texture 
    canvas.updateTexture(function(canvasElem, context) { });
// canvas.updateTexture(callback, scope);

Load or save texture

  • Save canvas to texuture 
    canvas.generateTexture(key);
// canvas.generateTexture(key, x, y, width, height);
  • Copy canvas from texture 
    canvas.loadTexture(key, frame);

Paste frame

canvas.drawFrame(key, frame);
// canvas.drawFrame(key, frame, dx, dy, dWidth, dHeight);
// canvas.drawFrame(key, frame, dx, dy, dWidth, dHeight, sxOffset, syOffset, sWidth, sHeight);
  • dx, dy : Top-left position in this canvas. Default value is 0, 0.
  • dWidth, dHeight : The size to draw the image in this canvas. Default value is origin size of frame.
  • sxOffset, syOffset : Offset position of source frame. Default value is 0, 0
  • sWidth, sHeight : The size of the sub-rectangle of the source frame to draw into this canvas. Default value is origin size of frame.

Data URL

  • Load image from URL 
    canvas.loadFromURL(url);
// canvas.loadFromURL(url, callback);
    or 
    canvas.loadFromURLPromise(url)
    .then(function() {

    })
    • url : Image url/uri(base64 string)
    • callback : Load complete callback.
  • Get data URL of image 
    var dataURL = canvas.getDataURL();
// var dataURL = canvas.getDataURL(type, encoderOptions);
    • dataURL : A base64 string.
    • type : A DOMString indicating the image format. The default format type is image/png.
    • encoderOptions : A Number between 0 and 1 indicating the image quality to use for image formats that use lossy compression such as image/jpeg and image/webp.

File

  • Load image from File object 
    canvas.loadFromFile(file);
// canvas.loadFromFile(file, callback);
    or 
    canvas.loadFromFilePromise(file)
    .then(function() {

    })
    • file : File object
    • callback : Load complete callback.

Pixel color

  • Get color 
    var color = canvas.getPixel(x, y);
    • color : Color object
      • color.red, color.green, color.blue, color.alpha
  • Set color 
    canvas.setPixel(x, y, r, g, b);
// canvas.setPixel(x, y, r, g, b, a);
    or 
    canvas.setPixel(x, y, color);
    • r, g, b, a : Integer number between 0 ~ 255.
    • color : Color object

Size

canvas.setCanvasSize(width, height);

or

canvas.setSize(width, height);

or

canvas.resize(width, height);

Other properties

See game object

Create mask

var mask = canvas.createBitmapMask();

See mask

Shader effects

Support preFX and postFX effects

Compare with Graphics object

  • Drawing method
    • This canvas object draws stuff on canvas in WEBGL or CANVAS render mode.
    • Graphics object draws stuff on webgl render pipeline in WEBGL render mode.
  • Size
    • This canvas object has size (width, height) and origin.
    • Graphics object does not have size and origin.