如何在 fabricjs 中限制图像外的矩形 resizing/moving？

Question

我正在使用 fabricjs 并试图限制 moving/resizing 个图像外的矩形。

这是我目前所拥有的fiddle：Fiddle

代码：

var canvas = new fabric.Canvas('c');

canvas.add(new fabric.Circle({ radius: 30, fill: '#f55', top: 100, left: 100 }));
canvas.setBackgroundImage('http://www.beatnyama.com/wp-content/uploads/2015/05/assets.jpg', canvas.renderAll.bind(canvas));

this.__canvases.push(canvas);  

canvas.observe("object:moving", function(e){
    var obj = e.target;
    //code goes here to restrict moving/resizing outside image
});

我该如何实施？

Answer 1

在此处查看更新的 fiddle 或运行代码段。 http://jsfiddle.net/h2zvj3un/2/

基本上你不应该使用背景，因为你需要知道图像尺寸。使用普通图像更容易（在可读性方面，您可以获得与 backgroundImage 对象相同的效果），而不是事件，不可选择。并设置到 canvas.

的后面

在图像加载时保存其边界坐标。

在物体移动时计算物体边界框并检查它是否会触及图像框。如果它触及它，则使用最新的已知正确值恢复图像的顶部和左侧值。

  var canvas = new fabric.Canvas('canvas');
  var minX, minY, maxX, maxY;
  canvas.add(new fabric.Circle({ radius: 30, fill: '#f55', top: 100, left: 100 }));
  fabric.Image.fromURL('http://www.beatnyama.com/wp-content/uploads/2015/05/assets.jpg', function(img){
  img.evented=false;
  img.selectable=false;
  canvas.add(img);
  minX = img.oCoords.tl.x;
  maxX = img.oCoords.br.x;
  minY = img.oCoords.tl.y;
  maxY = img.oCoords.br.y;
  canvas.sendToBack(img);
  });

function checkmove(e) {
var obj = e.target;
  obj.setCoords();
  var b = obj.getBoundingRect();
  if (!(b.left >= minX && maxX >= b.left + b.width)) {
  obj.left = obj.lastLeft;
  obj.scaleX= obj.lastScaleX
  obj.scaleY= obj.lastScaleY
  } else {
  obj.lastLeft = obj.left;
  obj.lastScaleX = obj.scaleX
  }
  if (!(maxY >= b.top + b.height && b.top >= minY)) {
  obj.top = obj.lastTop;
  obj.scaleX= obj.lastScaleX
  obj.scaleY= obj.lastScaleY
  } else {
  obj.lastTop = obj.top;
  obj.lastScaleY = obj.scaleY
  }
}
function checkscale(e) {
var obj = e.target;
  obj.setCoords();
  var b = obj.getBoundingRect();
  if (!(b.left >= minX && maxX >= b.left + b.width && maxY >= b.top + b.height && b.top >= minY)) {
  obj.left = obj.lastLeft;
  obj.top = obj.lastTop;
  obj.scaleX= obj.lastScaleX
  obj.scaleY= obj.lastScaleY
  } else {
  obj.lastLeft = obj.left;
  obj.lastTop = obj.top;
  obj.lastScaleX = obj.scaleX
  obj.lastScaleY = obj.scaleY      
  }
}
canvas.observe("object:moving", checkmove);
canvas.observe("object:scaling", checkscale);

<script src="http://fabricjs.com/lib/fabric.js"></script>
<canvas id='canvas' width="550" height="550" style="border:#000 1px solid;"></canvas>

如何在 fabricjs 中限制图像外的矩形 resizing/moving？

how to restrict rectangle resizing/moving outside a image in fabricjs?

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