Fabric.js 的簡單介紹和使用 (二）

以前咱們學習了基礎用法 如今咱們開始一些好玩的

Animation

咱們先回顧設置一下正方形角度方法

rect.set('angle', 45);

這是沒有動畫的

Fabric object都有animate方法

rect.animate('angle', 45, {
  onChange: canvas.renderAll.bind(canvas)
});

那麼正方形會從0到45有一個動畫過分

從左到右進行變更

rect.animate('left', '+=100', { onChange: canvas.renderAll.bind(canvas) });

逆時針轉5度

rect.animate('angle', '-=5', { onChange: canvas.renderAll.bind(canvas) });

固然animate還支持這些方法

1. from: Allows to specify starting value of animatable property (if we don't want 2. current value to be used).

2. duration: Defaults to 500 (ms). Can be used to change duration of an animation.

3. onComplete: Callback that's invoked at the end of the animation.

4. easing: Easing function.

rect.animate('left', '+=100', {
    onChange: canvas.renderAll.bind(canvas),
    duration: 3000,
    easing: fabric.util.ease.easeOutBounce
});

Image filters

圖片能夠使用filter效果

fabric.Image.fromURL('pug.jpg', function(img) {

  // add filter
  img.filters.push(new fabric.Image.filters.Grayscale());

  // apply filters and re-render canvas when done
  img.applyFilters(canvas.renderAll.bind(canvas));

  // add image onto canvas
  canvas.add(img);
});

filter一次能夠使用多個效果

固然 你也能夠本身定義filter

fabric.Image.filters.Redify = fabric.util.createClass({

  type: 'Redify',

  applyTo: function(canvasEl) {
    var context = canvasEl.getContext('2d'),
        imageData = context.getImageData(0, 0, canvasEl.width, canvasEl.height),
        data = imageData.data;

    for (var i = 0, len = data.length; i < len; i += 4) {
      data[i + 1] = 0;
      data[i + 2] = 0;
    }

    context.putImageData(imageData, 0, 0);
  }
});

fabric.Image.filters.Redify.fromObject = function(object) {
  return new fabric.Image.filters.Redify(object);
};

Colors

fabric 支持 hex rgb rgba顏色

new fabric.Color('#f55');
new fabric.Color('#123123');
new fabric.Color('356735');
new fabric.Color('rgb(100,0,100)');
new fabric.Color('rgba(10, 20, 30, 0.5)');

而且支持相互轉換

new fabric.Color('#f55').toRgb(); // "rgb(255,85,85)"
new fabric.Color('rgb(100,100,100)').toHex(); // "646464"
new fabric.Color('fff').toHex(); // "FFFFFF"

兩種顏色能夠疊加 而且你能夠使用一些特定效果

var redish = new fabric.Color('#f55');
var greenish = new fabric.Color('#5f5');

redish.overlayWith(greenish).toHex(); // "AAAA55"
redish.toGrayscale().toHex(); // "A1A1A1"

Gradients

能夠使用漸變色

var circle = new fabric.Circle({
  left: 100,
  top: 100,
  radius: 50
});

circle.setGradient('fill', {
  x1: 0,
  y1: -circle.height / 2,
  x2: 0,
  y2: circle.height / 2,
  colorStops: {
    0: '#000',
    1: '#fff'
  }
});

首先肯定兩個點 在其距離中以百分比定位顏色

circle.setGradient('fill', {
  x1: -circle.width / 2,
  y1: 0,
  x2: circle.width / 2,
  y2: 0,
  colorStops: {
    0: "red",
    0.2: "orange",
    0.4: "yellow",
    0.6: "green",
    0.8: "blue",
    1: "purple"
  }
});

Text

1. Multiline support. Native text methods unfortunately simply ignore new lines.

2. Text alignment. Left, center, right. Useful when working with multiline text.

3. Text background. Background also respects text alignment.

4. Text decoration. Underline, overline, strike-through.

5. Line height. Useful when working with multiline text.

如何添加文字

var text = new fabric.Text('hello world', { left: 100, top: 100 });
canvas.add(text);

fontFamily

var comicSansText = new fabric.Text("I'm in Comic Sans", {
  fontFamily: 'Comic Sans'
});

fontSize

var text40 = new fabric.Text("I'm at fontSize 40", {
  fontSize: 40
});
var text20 = new fabric.Text("I'm at fontSize 20", {
  fontSize: 20
});

fontWeight

var normalText = new fabric.Text("I'm a normal text", {
  fontWeight: 'normal'
});
var boldText = new fabric.Text("I'm at bold text", {
  fontWeight: 'bold'
});

textDecoration

var underlineText = new fabric.Text("I'm an underlined text", {
  textDecoration: 'underline'
});
var strokeThroughText = new fabric.Text("I'm a stroke-through text", {
  textDecoration: 'line-through'
});
var overlineText = new fabric.Text("I'm an overline text", {
  textDecoration: 'overline'
});

shadow

var shadowText1 = new fabric.Text("I'm a text with shadow", {
  shadow: 'rgba(0,0,0,0.3) 5px 5px 5px'
});
var shadowText2 = new fabric.Text("And another shadow", {
  shadow: 'rgba(0,0,0,0.2) 0 0 5px'
});
var shadowText3 = new fabric.Text("Lorem ipsum dolor sit", {
  shadow: 'green -5px -5px 3px'
});

fontStyle

var italicText = new fabric.Text("A very fancy italic text", {
  fontStyle: 'italic',
  fontFamily: 'Delicious'
});
var anotherItalicText = new fabric.Text("another italic text", {
  fontStyle: 'italic',
  fontFamily: 'Hoefler Text'
});

stroke & strokeWidth

var textWithStroke = new fabric.Text("Text with a stroke", {
  stroke: '#ff1318',
  strokeWidth: 1
});
var loremIpsumDolor = new fabric.Text("Lorem ipsum dolor", {
  fontFamily: 'Impact',
  stroke: '#c3bfbf',
  strokeWidth: 3
});

textAlign

var text = 'this is\na multiline\ntext\naligned right!';
var alignedRightText = new fabric.Text(text, {
  textAlign: 'right'
});

lineHeight

var lineHeight3 = new fabric.Text('Lorem ipsum ...', {
  lineHeight: 3
});
var lineHeight1 = new fabric.Text('Lorem ipsum ...', {
  lineHeight: 1
});

textBackgroundColor

var text = 'this is\na multiline\ntext\nwith\ncustom lineheight\n&background';
var textWithBackground = new fabric.Text(text, {
  textBackgroundColor: 'rgb(0,200,0)'
})

Events

怎麼能夠沒有事件呢

事件以on off使用 canvas 能夠捕捉事件

mouseevent
"mouse:down", "mouse:move", and "mouse:up".

renderevent
"after:render".

selectionevent
"before:selection:cleared", "selection:created", "selection:cleared".

objectevent
object ones: "object:modified", "object:selected", "object:moving", "object:scaling", "object:rotating", "object:added", and "object:removed"

var canvas = new fabric.Canvas('...');
canvas.on('mouse:down', function(options) {
  console.log(options.e.clientX, options.e.clientY);
});

一樣這些事件也能夠用任何fabric對象監聽

var rect = new fabric.Rect({ width: 100, height: 50, fill: 'green' });
rect.on('selected', function() {
  console.log('selected a rectangle');
});

var circle = new fabric.Circle({ radius: 75, fill: 'blue' });
circle.on('selected', function() {
  console.log('selected a circle');
});