fabric.js抵消解决方案 [英] fabric.js Offset Solution
问题描述
在用fabric.js处理偏移量时-最好的方法是什么?
In dealing with offset with fabric.js - what is the best approach?
我基本上是允许用户绘制一个框,并且我想确保已在拖动动作的确切开始和结束坐标处绘制了该框.
I'm basically allowing a user to draw a box, and I want to make sure I have the box drawn at the exact start and ending coordinates of the dragging action.
http://jsfiddle.net/mojo5000/P7gAC/4/
...
left: x + width/2 - 8,
top: y + height/2 - 8,
...
我基本上不得不对左值和顶值进行一些操作.看来行得通.有更好的方法吗?
I basically had to a little rigging with the left and top values. It seems to work. Is there a better way to do this?
推荐答案
您尚未考虑canvas元素的位置. 使用以下内容:
You have not factored in the positioning of the canvas element. Use the following:
var canvas = new fabric.Canvas('c');
canvas.on("after:render", function(){canvas.calcOffset();});
var started = false;
var x = 0;
var y = 0;
var width = 0;
var height = 0;
canvas.on('mouse:down', function(options) {
//console.log(options.e.clientX, options.e.clientY);
x = options.e.clientX;
y = options.e.clientY;
canvas.on('mouse:up', function(options) {
width = options.e.clientX - x;
height = options.e.clientY - y;
var square = new fabric.Rect({
width: width,
height: height,
left: x + width/2 - canvas._offset.left,
top: y + height/2 - canvas._offset.top,
fill: 'red',
opacity: .2
});
canvas.add(square);
canvas.off('mouse:up');
$('#list').append('<p>Test</p>');
});
});
正如您在代码中看到的那样,canvas元素的坐标由以下元素给出:canvas._offset.left
和canvas._offset.top
As you can see in the code, the coordinates of the canvas element are given by: canvas._offset.left
and canvas._offset.top
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