我一直在尝试让一个对象(在画布上使用fabric js构建)始终保持在边界内。在移动和旋转它时已经实现了这一点。我参考了Move object within canvas boundary limit来实现这一点。但是,当我开始缩放对象时,它就会简单地超出边界。我不明白如何才能使它在缩放时仍然保持在边界内。请帮我编写代码以防止这种行为,并附上演示。
<html>
<head>
<title>Basic usage</title>
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.3/fabric.min.js"></script>
</head>
<body>
<canvas id="canvas" style= "border: 1px solid black" height= 480 width = 360></canvas>
<script>
var canvas = new fabric.Canvas('canvas');
canvas.add(new fabric.Circle({ radius: 30, fill: '#f55', top: 100, left: 100 }));
canvas.item(0).set({
borderColor: 'gray',
cornerColor: 'black',
cornerSize: 12,
transparentCorners: true
});
canvas.setActiveObject(canvas.item(0));
canvas.renderAll();
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);
}
});
</script>
</body>
</html>
此处附上我的演示代码: https://jsfiddle.net/3v0cLaLk/
(注:演示代码是一个网址链接)
Math.max
?例如:obj.top = obj.top - obj.getBoudingRect().top
不就足够了吗?我找不到一个这样的情况,即Math.max(obj.top, obj.top-obj.getBoundingRect().top);
中obj.top
会被视为obj.getBoundingRect().top
始终为负数。 - broadband