在画布边界限制内移动对象答案

【问题标题】：Move object within canvas boundary limit在画布边界限制内移动对象
【发布时间】：2014-05-19 13:58:57
【问题描述】：

我试图限制画布内的移动对象，但是在顶部和左侧的限制区域中移动对象时遇到了一些困难，当我将对象缩放得更大时，我也无法限制移动画布左侧和顶部的对象

canvas.observe("object:moving", function(e) {
  var obj = e.target;
  // if object is too big ignore
  if(obj.currentHeight > obj.canvas.height || obj.currentWidth > obj.canvas.width) {
    return;
  }

  var halfw = obj.currentWidth/2;
  var halfh = obj.currentHeight/2;
  var bounds = {
    tl: {x: halfw, y:halfh},
    br: {x: obj.canvas.width-halfw, y: obj.canvas.height-halfh}
  };

  // top-left  corner
  if(obj.top < bounds.tl.y || obj.left < bounds.tl.x) {
    obj.top = Math.max(obj.top, bounds.tl.y);
    obj.left = Math.max(obj.left, bounds.tl.x )
  }
        
  // bot-right corner
  if(obj.top > bounds.br.y || obj.left > bounds.br.x) {
    obj.top = Math.min(obj.top, bounds.br.y);
    obj.left = Math.min(obj.left, bounds.br.x)
  }
});

【问题讨论】：

标签： javascript canvas fabricjs

【解决方案1】：

canvas.on('object:moving', function (e) {
  var obj = e.target;
  // if object is too big ignore
  if(obj.currentHeight > obj.canvas.height || obj.currentWidth > obj.canvas.width){
    return;
  }
  obj.setCoords();
  // top-left  corner
  if(obj.getBoundingRect().top < 0 || obj.getBoundingRect().left < 0){
    obj.top = Math.max(obj.top, obj.top-obj.getBoundingRect().top);
    obj.left = Math.max(obj.left, obj.left-obj.getBoundingRect().left);
  }
  // bot-right corner
  if(obj.getBoundingRect().top+obj.getBoundingRect().height  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width  > obj.canvas.width){
    obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top);
    obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left);
  }
});

【讨论】：

我见过的最佳解决方案。
如果您需要允许将对象部分移动到画布边界之外，请参阅下面的增强功能
不错！是否可以覆盖织物功能，这样会影响所有织物画布？

【解决方案2】：

在这里你可以找到解决方案：-

var canvas = window._canvas = new fabric.Canvas('c');
canvas.selection = false;

fabric.Object.prototype.set({
    transparentCorners: false,
    cornerColor: 'red',
    cornerSize: 12,
    padding: 0
});
text = new fabric.Text('Sample',{
    top: canvas.height/2,
    left: canvas.width/2,
    fill: '#000000'
});

canvas.add(text);
canvas.setActiveObject(text);

canvas.observe('object:scaling', function (e) {
    var obj = e.target;
  if(obj.getHeight() > obj.canvas.height || obj.getWidth() > obj.canvas.width){
    obj.setScaleY(obj.originalState.scaleY);
    obj.setScaleX(obj.originalState.scaleX);        
  }
  obj.setCoords();
  if(obj.getBoundingRect().top - (obj.cornerSize / 2) < 0 || 
     obj.getBoundingRect().left -  (obj.cornerSize / 2) < 0) {
    obj.top = Math.max(obj.top, obj.top-obj.getBoundingRect().top + (obj.cornerSize / 2));
    obj.left = Math.max(obj.left, obj.left-obj.getBoundingRect().left + (obj.cornerSize / 2));    
  }
  if(obj.getBoundingRect().top+obj.getBoundingRect().height + obj.cornerSize  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width + obj.cornerSize  > obj.canvas.width) {

    obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top - obj.cornerSize / 2);
    obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left - obj.cornerSize /2);    
  }
});

canvas.observe('object:moving', function (e) {
    var obj = e.target;
  if(obj.getHeight() > obj.canvas.height || obj.getWidth() > obj.canvas.width){
    obj.setScaleY(obj.originalState.scaleY);
    obj.setScaleX(obj.originalState.scaleX);        
  }
  obj.setCoords();
  if(obj.getBoundingRect().top - (obj.cornerSize / 2) < 0 || 
     obj.getBoundingRect().left -  (obj.cornerSize / 2) < 0) {
    obj.top = Math.max(obj.top, obj.top-obj.getBoundingRect().top + (obj.cornerSize / 2));
    obj.left = Math.max(obj.left, obj.left-obj.getBoundingRect().left + (obj.cornerSize / 2));    
  }
  if(obj.getBoundingRect().top+obj.getBoundingRect().height + obj.cornerSize  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width + obj.cornerSize  > obj.canvas.width) {

    obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top - obj.cornerSize / 2);
    obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left - obj.cornerSize /2);    
  }
});

http://jsfiddle.net/jw1827fm/1/

【讨论】：

对于 1.7.11 版本的我来说，比例尺不适用。首先，您需要使用{stateful : true,} 构建织物画布。其次，我不得不使用_stateProperties 而不是originalState。第三，这些更改后您需要obj.saveState();。

【解决方案3】：

只需在你的 js 文件中添加以下代码，并根据你的画布高度和宽度更改缩放 X(left) 和 Y(top) 的值。

// canvas moving limit 

canvas.observe("object:moving", function(e){
      var obj = e.target;
         // if object is too big ignore

        var halfw = obj.currentWidth/2;
        var halfh = obj.currentHeight/2;
        var bounds = {tl: {x: halfw, y:halfh},
            br: {x: obj.canvas.width , y: obj.canvas.height }
        };

        // top-left  corner



            // alert("text");
        if(obj.top < bounds.tl.y || obj.left < bounds.tl.x){
            obj.top = Math.max(obj.top, '10'  );
            obj.left = Math.max(obj.left , '50' ) 
        }


        // bot-right corner
        if(obj.top > bounds.br.y || obj.left > bounds.br.x ){
            obj.top = Math.min(obj.top, '360'  );  
            obj.left = Math.min(obj.left, '470' )  
        }

});
// end canvas moving limit

【讨论】：

是否有强制对象离开画布的方法？
在堆栈上提问
这只是是或否的问题，如果是，那么如何？不需要额外的问题。 Stack 有非常自私的社区版主，如果我只是问问题，他们会以否定的方式结束问题。

【解决方案4】：

我只是修改了 Balaji 的代码，现在效果更好了

canvas.on('object:moving', function (e) {
    var obj = e.target;

     // if object is too big ignore
    if(obj.getScaledHeight() > obj.canvas.height || obj.getScaledWidth() > obj.canvas.width){
        return;
    }        
    obj.setCoords();        
    // top-left  corner
    if(obj.getBoundingRect().top < 0 || obj.getBoundingRect().left < 0){
        obj.top = Math.max(obj.top, obj.top-obj.getBoundingRect().top);
        obj.left = Math.max(obj.left, obj.left-obj.getBoundingRect().left);
    }
    // bot-right corner
    if(obj.getBoundingRect().top+obj.getBoundingRect().height  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width  > obj.canvas.width){
        obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top);
        obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left);
    }});

【讨论】：

【解决方案5】：

由于我需要这个，这里是我基于 Balaji 的代码设置偏移量的过度工作函数，因此对象只能部分显示在画布中。

canvas.on('object:moving', function (e) {
      var obj = e.target;

      // if object is too big ignore
      if(obj.currentHeight > obj.canvas.height || obj.currentWidth > obj.canvas.width){
          return;
      }        

      // set offset for moving out the canvas (20 % of object persists in canvas)
      var offsetWidth = obj.getBoundingRect().width * 0.8;
      var offsetHeight = obj.getBoundingRect().height * 0.8;

      obj.setCoords();        

      // top-left  corner
      if(obj.getBoundingRect().top < -offsetHeight || obj.getBoundingRect().left < -offsetWidth){
          obj.top = Math.max(obj.top, obj.top-(obj.getBoundingRect().top+offsetHeight));
          obj.left = Math.max(obj.left, obj.left-(obj.getBoundingRect().left+offsetWidth));
      }
      // bot-right corner
      if(obj.getBoundingRect().top+obj.getBoundingRect().height  > obj.canvas.height + offsetHeight || obj.getBoundingRect().left+obj.getBoundingRect().width  > obj.canvas.width + offsetWidth){
          obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top+offsetHeight);
          obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left+offsetWidth);
      }
});

【讨论】：

【解决方案6】：

只是稍微修改了 Balaji 和 Surya T 的代码，所以它现在可以完全处理画布缩放设置。

   _self.layer.on('object:moving', function (e) {
        var obj = e.target;

        obj.setCoords();
        var curZoom = obj.canvas.getZoom();

        //
        // if object is too big ignore
        if(obj.getScaledHeight() > obj.canvas.height || obj.getScaledWidth() > obj.canvas.width){
            return;
        }

        // top-left  corner
        if(obj.getBoundingRect().top < 0 || obj.getBoundingRect().left < 0){
            obj.top = Math.max(obj.top*curZoom, obj.top*curZoom-obj.getBoundingRect().top)/curZoom;
            obj.left = Math.max(obj.left*curZoom, obj.left*curZoom-obj.getBoundingRect().left)/curZoom;
        }
        // bot-right corner
        if(obj.getBoundingRect().top+obj.getBoundingRect().height  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width  > obj.canvas.width){
            obj.top = Math.min(obj.top*curZoom, obj.canvas.height-obj.getBoundingRect().height+obj.top*curZoom-obj.getBoundingRect().top)/curZoom;
            obj.left = Math.min(obj.left*curZoom, obj.canvas.width-obj.getBoundingRect().width+obj.left*curZoom-obj.getBoundingRect().left)/curZoom;
        }
    });

【讨论】：