如何select只在透明背景矩形中描边？

Question

如何才能使透明矩形 select只有在我点击描边时才可用？我尝试了两种不同的方法，您可以从下面的代码片段中看到，左侧的对象是具有透明背景的矩形，右侧的对象是具有多条线的组对象。我想知道如何才能 select 元素只有当我点击笔划时，如果你点击内部透明区域，两个对象都会变成 selected.

var canvas = new fabric.Canvas('a');
canvas.add(new fabric.Rect({
  left: 10,
  top: 20,
  height: 160,
  width: 80,
  fill: 'transparent',
  stroke: 'red'
}));
var rectLine1 = new fabric.Line([0, 0, 80, 0], {
  stroke: 'red',
  left: 100,
  top: 20
});
var rectLine2 = new fabric.Line([0, 160, 0, 0], {
  stroke: 'red',
  left: 100,
  top: 20
});
var rectLine3 = new fabric.Line([0, 160, 0, 0], {
  stroke: 'red',
  left: 180,
  top: 20
});
let rectLine4 = new fabric.Line([0, 0, 80, 0], {
  stroke: 'red',
  left: 100,
  top: 180
});
var group = new fabric.Group([rectLine1, rectLine2, rectLine3, rectLine4], {
  left: 110,
  top: 20
})
canvas.add(group)
canvas.renderAll();

.c {
  border: 2px solid black;
}

<script
  src="https://code.jquery.com/jquery-2.2.4.min.js"
  integrity="sha256-BbhdlvQf/xTY9gja0Dq3HiwQF8LaCRTXxZKRutelT44="
  crossorigin="anonymous"></script>
<script type='text/javascript' src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.19/fabric.js"></script>
<canvas id="a" class="c" width="200" height="200"></canvas>

Answer 1

我发现设置 perPixelTargetFind: true 可以解决问题，您还可以在 canvas targetFindTolerance: 10 上设置容差，以便能够 select 具有细笔触的对象。我会在下面粘贴工作代码以备不时之需。

var canvas = new fabric.Canvas('a', {
  targetFindTolerance: 10
});
canvas.add(new fabric.Rect({
  left: 10,
  top: 20,
  height: 160,
  width: 80,
  fill: 'transparent',
  stroke: 'red',
  perPixelTargetFind: true,
}));
canvas.renderAll();

.c {
  border: 2px solid black;
}

<script
  src="https://code.jquery.com/jquery-2.2.4.min.js"
  integrity="sha256-BbhdlvQf/xTY9gja0Dq3HiwQF8LaCRTXxZKRutelT44="
  crossorigin="anonymous"></script>
<script type='text/javascript' src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.19/fabric.js"></script>
<canvas id="a" class="c" width="200" height="200"></canvas>

如何select只在透明背景矩形中描边？

How to select only the stroke in a transparent backgroud rectangle?

javascript

canvas

fabricjs