Question

我刚开始使用Fabric.js（我不得不说，我印象深刻）。

我想在Fabric对象上添加一个网格。在下面的代码中，我将网格画布正好放在Fabric画布上。这里的问题是，我现在无法移动我的布料对象！

<!DOCTYPE html>
<html>
<head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">

  <script type='text/javascript' src='http://code.jquery.com/jquery-1.7.1.js'></script>
  <script type='text/javascript' src='http://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.2.0/fabric.all.min.js'></script>

</head>
<body>

<div style="height:480px;width:640px;border:1px solid #ccc;position:relative;font:16px/26px Georgia, Garamond, Serif;overflow:auto;">

 <canvas id="rubber" width="800" height="800" 
   style="position: absolute; left: 0; top: 0; z-index: 0;"></canvas>
 <canvas id="myCanvas" width="800" height="800" 
   style="position: absolute; left: 0; top: 0; z-index: 1;"></canvas>
</div>

<script>
//<![CDATA[ 
$(window).load(function(){
$(document).ready(function () {

    function renderGrid(x_size,y_size, color)
    {
        var canvas = $("#myCanvas").get(0);
        var context = canvas.getContext("2d");

        context.save();
        context.lineWidth = 0.5;
        context.strokeStyle = color;

        // horizontal grid lines
        for(var i = 0; i <= canvas.height; i = i + x_size)
        {
            context.beginPath();
            context.moveTo(0, i);
            context.lineTo(canvas.width, i);
            context.closePath();
            context.stroke();
        }

        // vertical grid lines
        for(var j = 0; j <= canvas.width; j = j + y_size)
        {
            context.beginPath();
            context.moveTo(j, 0);
            context.lineTo(j, canvas.height);
            context.closePath();
            context.stroke();
        }

        context.restore();
    }

    renderGrid(10,15, "gray");
});

});//]]>  

  var canvas = new fabric.Canvas('rubber');
  canvas.add(new fabric.Circle({ radius: 30, fill: '#f55', top: 100, left: 100 }));

  canvas.selectionColor = 'rgba(0,255,0,0.3)';
  canvas.selectionBorderColor = 'red';
  canvas.selectionLineWidth = 5;
</script>


</body>
</html>

我希望在Fabric本身有一种方法可以做到这一点。

任何帮助都会很棒，谢谢！

Answer 1

这两行代码将起作用：

var gridsize = 5;
for(var x=1;x<(canvas.width/gridsize);x++)
                        {
                            canvas.add(new fabric.Line([100*x, 0, 100*x, 600],{ stroke: "#000000", strokeWidth: 1, selectable:false, strokeDashArray: [5, 5]}));
                            canvas.add(new fabric.Line([0, 100*x, 600, 100*x],{ stroke: "#000000", strokeWidth: 1, selectable:false, strokeDashArray: [5, 5]}));
                    }

Answer 2

更短的版本，更通用的复制/粘贴：

var oCanvas; // must be your canvas object
var gridWidth; // <= you must define this with final grid width
var gridHeight; // <= you must define this with final grid height

// to manipulate grid after creation
var oGridGroup = new fabric.Group([], {left: 0, top: 0});

var gridSize = 20; // define grid size

// define presentation option of grid
var lineOption = {stroke: 'rgba(0,0,0,.4)', strokeWidth: 1, selectable:false, strokeDashArray: [3, 3]};

// do in two steps to limit the calculations
// first loop for vertical line
for(var i = Math.ceil(gridWidth/gridSize); i--;){
    oGridGroup.add( new fabric.Line([gridSize*i, 0, gridSize*i, gridHeight], lineOption) );
}
// second loop for horizontal line
for(var i = Math.ceil(gridHeight/gridSize); i--;){
    oGridGroup.add( new fabric.Line([0, gridSize*i, gridWidth, gridSize*i], lineOption) );
}
// Group add to canvas
oCanvas.add(oGridGroup);

Answer 3

我的解决方案是 -

var width = canvas.width;
var height = canvas.height;

var j = 0;
var line = null;
var rect = [];
var size = 20;

console.log(width + ":" + height);

for (var i = 0; i < Math.ceil(width / 20); ++i) {
    rect[0] = i * size;
    rect[1] = 0;

    rect[2] = i * size;
    rect[3] = height;

    line = null;
    line = new fabric.Line(rect, {
        stroke: '#999',
        opacity: 0.5,
    });

    line.selectable = false;
    canvas.add(line);
    line.sendToBack();

}

for (i = 0; i < Math.ceil(height / 20); ++i) {
    rect[0] = 0;
    rect[1] = i * size;

    rect[2] = width;
    rect[3] = i * size;

    line = null;
    line = new fabric.Line(rect, {
        stroke: '#999',
        opacity: 0.5,
    });
    line.selectable = false;
    canvas.add(line);
    line.sendToBack();

}

canvas.renderAll();

你必须保存所有行对象以删除网格，或者你可以将所有行对象添加到一个组中，你可以删除该组以删除网格，我认为这不是优雅的，但有效。

Answer 4

如果您不坚持动态生成网格，可能需要考虑fabric.js提供的原生叠加图像功能。

var canvas = new fabric.Canvas('rubber');
canvas.setOverlayImage('grid.png', canvas.renderAll.bind(canvas));

它根本不会妨碍与画布上的对象的交互。

Answer 5

我希望这会对你有帮助----

function draw_grid(grid_size) {

  grid_size || (grid_size = 25);
  currentCanvasWidth = canvas.getWidth();
  currentcanvasHeight = canvas.getHeight();


  // Drawing vertical lines
  var x;
  for (x = 0; x <= currentCanvasWidth; x += grid_size) {
      this.grid_context.moveTo(x + 0.5, 0);
      this.grid_context.lineTo(x + 0.5, currentCanvasHeight);
  }

  // Drawing horizontal lines
  var y;
  for (y = 0; y <= currentCanvasHeight; y += grid_size) {
      this.grid_context.moveTo(0, y + 0.5);
      this.grid_context.lineTo(currentCanvasWidth, y + 0.5);
  }

  grid_size = grid_size;
  this.grid_context.strokeStyle = "black";
  this.grid_context.stroke();
}

Answer 6

这是我的解决方案，可与Fabric Js 4一起使用。最后，有两个事件侦听器，它们在对象移动时追加网格，并在对象移动结束时删除网格。（改进@draeli的答案https://stackoverflow.com/a/35936606/1727357）

(function () {
    const gcd = (a, b) => {
        if (!b) {
            return a;
        }
        return gcd(b, a % b);
    }
    const gridWidth = canvas.getWidth();
    const gridHeight = canvas.getHeight();

    const oGridGroup = [];
    console.log(gcd(gridWidth, gridHeight));

    const gridRows = gcd(gridWidth, gridHeight);
    const gridCols = gcd(gridWidth, gridHeight);

    const lineOption = { stroke: 'rgba(0,0,0,.1)', strokeWidth: 1, selectable: false, evented: false };

    for (let i = 0; i <= gridWidth; i += gridCols) {
        oGridGroup.push(new fabric.Line([i, 0, i, gridHeight], lineOption));
    }
    for (let i = 0; i <= gridHeight; i += gridRows) {
        oGridGroup.push(new fabric.Line([0, i, gridWidth, i], lineOption));
    }

    const theGorup = new fabric.Group(oGridGroup);
    theGorup.set({
        selectable: false,
        evented: false
    })

    canvas.on('mouse:down', function (event) {
        if (event.target) {
            canvas.add(theGorup);
        }
    });

    canvas.on('mouse:up', function (event) {
        canvas.remove(theGorup);

    });

}())

Answer 7

已更新：

答案基于rafi发布的代码：

我已经更新了缺少的grid_context。
请用字符串中的画布ID替换“ <您的画布ID>”。例如“ myCanvas”。

通常，您在画布上执行的任何操作都将清除画布上的网格，在fabric.js画布上注册after：render事件以重绘它。这样您就可以始终看到它。

 var canvas = new fabric.Canvas(<your canvas Id>);
 canvas.on('after:render',function(ctx){
       draw_grid(25);
 });

 function draw_grid(grid_size) {
    grid_size || (grid_size = 25);
    var currentCanvas = document.getElementById(<your canvas Id>); 
    var grid_context = currentCanvas.getContext("2d"); 

    var currentCanvasWidth = canvas.getWidth();
    var currentCanvasHeight = canvas.getHeight();

    // Drawing vertical lines
    var x;
    for (x = 0; x <= currentCanvasWidth; x += grid_size) {
       grid_context.moveTo(x + 0.5, 0);
       grid_context.lineTo(x + 0.5, currentCanvasHeight);
    }

    // Drawing horizontal lines
    var y;
    for (y = 0; y <= currentCanvasHeight; y += grid_size) {
      grid_context.moveTo(0, y + 0.5);
      grid_context.lineTo(currentCanvasWidth, y + 0.5);
    }
   grid_context.strokeStyle = "#0000002b";
   grid_context.stroke();
 }

Answer 8

我真的很喜欢@Draeli的回答，但似乎不适用于最新的Fabric版本。修复了旧的问题，并增加了一个对我自己必要的轻微调整-将网格居中。

无论如何，也许有人觉得它有用：

const gridSize = 100;
const width = this.canvas.getWidth();
const height = this.canvas.getHeight();
const left = (width % gridSize) / 2;
const top = (height % gridSize) / 2;
const lines = [];
const lineOption = {stroke: 'rgba(0,0,0,1)', strokeWidth: 1, selectable: false};
for (let i = Math.ceil(width / gridSize); i--;) {
  lines.push(new fabric.Line([gridSize * i, -top, gridSize * i, height], lineOption));
}
for (let i = Math.ceil(height / gridSize); i--;) {
  lines.push(new fabric.Line([-left, gridSize * i, width, gridSize * i], lineOption));
}
const oGridGroup = new fabric.Group(lines, {left: 0, top: 0});

this.canvas.add(oGridGroup);

this.canvas-这应该是结构实例。

在Fabric.js画布上添加网格

8 个答案: