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HTML5 Canvas 图形选择、调整尺寸和旋转

Transformer 是一种特殊的 Konva.Group。使用它可以调整任意节点或一组节点的尺寸并旋转这些节点。

要启用它，请执行以下操作：

  1. 使用 new Konva.Transformer() 创建新实例
  2. 将它添加到图层
  3. 使用 transformer.nodes([shape]); 将它附加到节点

注意： 调整节点尺寸时，变换工具不会更改节点的 width 和 height 属性。它会改为更改 scaleX 和 scaleY 属性。

操作说明：尝试调整图形尺寸并旋转图形。单击空白区域可取消选择。使用 SHIFT 或 CTRL 将图形添加到选区或从选区移除。尝试在 Canvas 上框选一个区域。

import Konva from 'konva';

const width = window.innerWidth;
const height = window.innerHeight;

const stage = new Konva.Stage({
  container: 'container',
  width: width,
  height: height,
});

const layer = new Konva.Layer();
stage.add(layer);

// create rectangle
const rect1 = new Konva.Rect({
  x: 60,
  y: 60,
  width: 100,
  height: 90,
  fill: 'red',
  name: 'rect',
  draggable: true,
});
layer.add(rect1);

const rect2 = new Konva.Rect({
  x: 250,
  y: 100,
  width: 150,
  height: 90,
  fill: 'green',
  name: 'rect',
  draggable: true,
});
layer.add(rect2);

// create transformer
const tr = new Konva.Transformer();
layer.add(tr);

// add a new feature, lets add ability to draw selection rectangle
let selectionRectangle = new Konva.Rect({
  fill: 'rgba(0,0,255,0.5)',
  visible: false,
});
layer.add(selectionRectangle);

let x1, y1, x2, y2;
stage.on('mousedown touchstart', (e) => {
  // do nothing if we mousedown on any shape
  if (e.target !== stage) {
  return;
  }
  x1 = stage.getPointerPosition().x;
  y1 = stage.getPointerPosition().y;
  x2 = stage.getPointerPosition().x;
  y2 = stage.getPointerPosition().y;

  selectionRectangle.setAttrs({
    x: x1,
    y: y1,
    width: 0,
    height: 0,
    visible: true,
  });
});

stage.on('mousemove touchmove', () => {
  // do nothing if we didn't start selection
  if (!selectionRectangle.visible()) {
  return;
  }
  x2 = stage.getPointerPosition().x;
  y2 = stage.getPointerPosition().y;

  selectionRectangle.setAttrs({
    x: Math.min(x1, x2),
    y: Math.min(y1, y2),
    width: Math.abs(x2 - x1),
    height: Math.abs(y2 - y1),
  });
});

stage.on('mouseup touchend', () => {
  // do nothing if we didn't start selection
  if (!selectionRectangle.visible()) {
    return;
  }
  // update visibility in timeout, so we can check it in click event
  setTimeout(() => {
    selectionRectangle.visible(false);
  });

  var shapes = stage.find('.rect');
  var box = selectionRectangle.getClientRect();
  var selected = shapes.filter((shape) =>
    Konva.Util.haveIntersection(box, shape.getClientRect())
  );
  tr.nodes(selected);
});

// clicks should select/deselect shapes
stage.on('click tap', function (e) {
// if we are selecting with rect, do nothing
if (selectionRectangle.visible() && selectionRectangle.width() > 0 && selectionRectangle.height() > 0) {
  return;
}

  // if click on empty area - remove all selections
  if (e.target === stage) {
    tr.nodes([]);
    return;
  }

  // do nothing if clicked NOT on our rectangles
  if (!e.target.hasName('rect')) {
    return;
  }

  // do we pressed shift or ctrl?
  const metaPressed = e.evt.shiftKey || e.evt.ctrlKey || e.evt.metaKey;
  const isSelected = tr.nodes().indexOf(e.target) >= 0;

  if (!metaPressed && !isSelected) {
    // if no key pressed and the node is not selected
    // select just one
    tr.nodes([e.target]);
  } else if (metaPressed && isSelected) {
    // if we pressed keys and node was selected
    // we need to remove it from selection:
    const nodes = tr.nodes().slice(); // use slice to have new copy of array
    // remove node from array
    nodes.splice(nodes.indexOf(e.target), 1);
    tr.nodes(nodes);
  } else if (metaPressed && !isSelected) {
    // add the node into selection
    const nodes = tr.nodes().concat([e.target]);
    tr.nodes(nodes);
  }
});
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