Fabric.js 简单介绍和使用（三）

xi4oh4o 发布于2019-08-19 18:04 / 2151人阅读

摘要：之前我们学习了基础和高级特性现在介绍更神奇的东西话说这个功能我最喜欢组成群组可以统一修改其中所有组件属性如何定义现在我们就可以对其中的对象集修改中的元素相对于定位但是由于要确保之前得到却切位置所以要异步可以动态添加添加并修改当然你可以使用

之前我们学习了基础和高级特性现在介绍更神奇的东西

Groups

话说这个功能我最喜欢

组成群组可以统一修改其中所有组件属性

如何定义

var circle = new fabric.Circle({
  radius: 100,
  fill: "#eef",
  scaleY: 0.5,
  originX: "center",
  originY: "center"
});

var text = new fabric.Text("hello world", {
  fontSize: 30,
  originX: "center",
  originY: "center"
});

var group = new fabric.Group([ circle, text ], {
  left: 150,
  top: 100,
  angle: -10
});

canvas.add(group);

现在我们就可以对其中的对象集修改

group.item(0).setFill("red");
group.item(1).set({
  text: "trololo",
  fill: "white"
});

group中的元素相对于group定位

但是由于要确保之前得到却切位置所以要异步

fabric.Image.fromURL("/assets/pug.jpg", function(img) {
  var img1 = img.scale(0.1).set({ left: 100, top: 100 });

  fabric.Image.fromURL("/assets/pug.jpg", function(img) {
    var img2 = img.scale(0.1).set({ left: 175, top: 175 });

    fabric.Image.fromURL("/assets/pug.jpg", function(img) {
      var img3 = img.scale(0.1).set({ left: 250, top: 250 });

      canvas.add(new fabric.Group([ img1, img2, img3], { left: 200, top: 200 }))
    });
  });
});

group 可以动态添加

group.add(new fabric.Rect({
  ...
  originX: "center",
  originY: "center"
}));

添加并修改group

group.addWithUpdate(new fabric.Rect({
  ...
  left: group.getLeft(),
  top: group.getTop(),
  originX: "center",
  originY: "center"
}));

当然你可以使用canvas上已有的进行克隆组合

// create a group with copies of existing (2) objects
var group = new fabric.Group([
  canvas.item(0).clone(),
  canvas.item(1).clone()
]);

// remove all objects and re-render
canvas.clear().renderAll();

// add group onto canvas
canvas.add(group);

Serialization

序列化是为了相互传输

toObject, toJSON

canvas 实现了toJSON接口可以被序列化

var canvas = new fabric.Canvas("c");
JSON.stringify(canvas); // "{"objects":[],"background":"rgba(0, 0, 0, 0)"}"

canvas 可以随时被修改 json数据会被修改

canvas.backgroundColor = "red";
JSON.stringify(canvas); // "{"objects":[],"background":"red"}"

添加新对象也会改变json数据

canvas.add(new fabric.Rect({
  left: 50,
  top: 50,
  height: 20,
  width: 20,
  fill: "green"
}));
console.log(JSON.stringify(canvas));

"{"objects":[{"type":"rect","left":50,"top":50,"width":20,"height":20,"fill":"green","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"rx":0,"ry":0}],"background":"rgba(0, 0, 0, 0)"}"

再添加一个

canvas.add(new fabric.Circle({
  left: 100,
  top: 100,
  radius: 50,
  fill: "red"
}));
console.log(JSON.stringify(canvas));

"{"objects":[{"type":"rect","left":50,"top":50,"width":20,"height":20,"fill":"green","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"rx":0,"ry":0},{"type":"circle","left":100,"top":100,"width":100,"height":100,"fill":"red","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"radius":50}],"background":"rgba(0, 0, 0, 0)"}"

toObject

可以转化成js object对象

{ "background" : "rgba(0, 0, 0, 0)",
  "objects" : [
    {
      "angle" : 0,
      "fill" : "green",
      "flipX" : false,
      "flipY" : false,
      "hasBorders" : true,
      "hasControls" : true,
      "hasRotatingPoint" : false,
      "height" : 20,
      "left" : 50,
      "opacity" : 1,
      "overlayFill" : null,
      "perPixelTargetFind" : false,
      "scaleX" : 1,
      "scaleY" : 1,
      "selectable" : true,
      "stroke" : null,
      "strokeDashArray" : null,
      "strokeWidth" : 1,
      "top" : 50,
      "transparentCorners" : true,
      "type" : "rect",
      "width" : 20
    }
  ]
}

每个fabric对象有toObject方法这和toJSON 也有关可以自定义

var rect = new fabric.Rect();
rect.toObject = function() {
  return { name: "trololo" };
};
canvas.add(rect);
console.log(JSON.stringify(canvas));

"{"objects":[{"name":"trololo"}],"background":"rgba(0, 0, 0, 0)"}"

当然我们可以保留原有的数据新增数据

var rect = new fabric.Rect();

rect.toObject = (function(toObject) {
  return function() {
    return fabric.util.object.extend(toObject.call(this), {
      name: this.name
    });
  };
})(rect.toObject);

canvas.add(rect);

rect.name = "trololo";

console.log(JSON.stringify(canvas))

"{"objects":[{"type":"rect","left":0,"top":0,"width":0,"height":0,"fill":"rgb(0,0,0)","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"rx":0,"ry":0,"name":"trololo"}],"background":"rgba(0, 0, 0, 0)"}"

toSvg

怎么能不支持转成svg呢

canvas.add(new fabric.Rect({
  left: 50,
  top: 50,
  height: 20,
  width: 20,
  fill: "green"
}));
console.log(canvas.toSVG());

""

Deserialization, SVG parser

fabric.Canvas#loadFromJSON
fabric.Canvas#loadFromDatalessJSON
fabric.loadSVGFromURL
fabric.loadSVGFromString

var canvas = new fabric.Canvas();

canvas.loadFromJSON("{"objects":[{"type":"rect","left":50,"top":50,"width":20,"height":20,"fill":"green","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"rx":0,"ry":0},{"type":"circle","left":100,"top":100,"width":100,"height":100,"fill":"red","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":0,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"radius":50}],"background":"rgba(0, 0, 0, 0)"}");

通常情况下 svg 会被序列化但是可以使用 fabric.Canvas#toDatalessJSON

canvas.item(0).sourcePath = "/assets/dragon.svg";
console.log(JSON.stringify(canvas.toDatalessJSON()));

{"objects":[{"type":"path","left":143,"top":143,"width":175,"height":151,"fill":"#231F20","overlayFill":null,"stroke":null,"strokeWidth":1,"strokeDashArray":null,"scaleX":1,"scaleY":1,"angle":-19,"flipX":false,"flipY":false,"opacity":1,"selectable":true,"hasControls":true,"hasBorders":true,"hasRotatingPoint":false,"transparentCorners":true,"perPixelTargetFind":false,"path":"/assets/dragon.svg"}],"background":"rgba(0, 0, 0, 0)"}

Subclassing

构造类

var Point = fabric.util.createClass({
  initialize: function(x, y) {
    this.x = x || 0;
    this.y = y || 0;
  },
  toString: function() {
    return this.x + "/" + this.y;
  }
});

继承类

var ColoredPoint = fabric.util.createClass(Point, {
  initialize: function(x, y, color) {
    this.callSuper("initialize", x, y);
    this.color = color || "#000";
  },
  toString: function() {
    return this.callSuper("toString") + " (color: " + this.color + ")";
  }
});

继承默认类

var LabeledRect = fabric.util.createClass(fabric.Rect, {

  type: "labeledRect",

  initialize: function(options) {
    options || (options = { });

    this.callSuper("initialize", options);
    this.set("label", options.label || "");
  },

  toObject: function() {
    return fabric.util.object.extend(this.callSuper("toObject"), {
      label: this.get("label")
    });
  },

  _render: function(ctx) {
    this.callSuper("_render", ctx);

    ctx.font = "20px Helvetica";
    ctx.fillStyle = "#333";
    ctx.fillText(this.label, -this.width/2, -this.height/2 + 20);
  }
});

不过其实没必要的

混合云专线服务 WebRtc的简单介绍 webrtc介绍及简单应用 html5的简单介绍 webrtc使用介绍

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Fabric.js 简单介绍和使用（三）

toObject, toJSON

toObject

toSvg

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