使用 KonvaJS 绘制和旋转图像答案

【问题标题】：Drawing and rotated images using KonvaJS使用 KonvaJS 绘制和旋转图像
【发布时间】：2020-07-01 17:26:40
【问题描述】：

所以我一直在尝试使用 Konva 来绘制图像、文本和形状的数量，一切都很好，直到我尝试在混合中添加旋转。我知道 Konva 使用原点（默认情况下可以通过偏移移动的左上角）来旋转图像，但我需要位置始终位于左上角。

所以我试图计算、旋转重新定位对象以模仿我想要的东西，但这总是导致图像位置与我的初始状态不同，这是一种不需要的行为。

所以我的问题是，Konva 可以从中心旋转图像，同时在旋转后保持原点位置在左上角吗？

*使用代码示例编辑：绿色框/文本旋转但位置全错。我需要在左边的位置。

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

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


const rotatePoint= (x, y , rad)=> {
  const rcos = Math.cos(rad);
  const rsin = Math.sin(rad);
  return {
    x: x * rcos - y * rsin,
    y: y * rcos + x * rsin
  }
}

const rotateAroundCenter = (node, rotation) => {  
  const topLeft = { x: -node.width() / 2, y: -node.height() / 2 };
  const current = rotatePoint(topLeft.x, topLeft.y, Konva.getAngle(node.rotation()));
  const rotated = rotatePoint(topLeft.x, topLeft.y, Konva.getAngle(rotation));
  const dx = rotated.x - current.x,
        dy = rotated.y - current.y;
  
  node.rotation(rotation); 
  
  node.x(node.x() + dx);
  node.y(node.y() + dy);
  
  return node;
}

let x = 100,
    y = 50, 
    width = 50,
    height = 50;
    

const rotation = 90;

const text = { width, height, fontSize: 15, fontFamily: 'Calibri', text: 'Simple Text', opacity: 0.5 };
const rect = { width, height, strokeWidth: 2}
let pos = {x, y};
layer.add(new Konva.Circle({ ...pos, radius:5, fill: 'black' })); 
layer.add(new Konva.Text({ ...pos, ...text, fill: 'black' })); 
layer.add(new Konva.Rect({ ...pos, ...rect, stroke: 'purple' })); 
layer.add(new Konva.Text({ ...pos, ...text, fill: 'purple', rotation: rotation })); 
layer.add(new Konva.Rect({ ...pos, ...rect, stroke: 'purple', rotation: rotation }));

pos = {x, y:150};

layer.add(new Konva.Circle({ ...pos, radius:5, fill: 'black' })); 
layer.add(rotateAroundCenter(new Konva.Text({ ...pos, ...text, fill: 'green' }), rotation)); 
layer.add(rotateAroundCenter(new Konva.Rect({ ...pos, ...rect, stroke: 'green' }), rotation)); 



layer.draw();

<!DOCTYPE html>
<html>
<head>
<meta name="description" content="KonvaJS Template">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/konva/4.2.0/konva.min.js"></script>
  <meta charset="utf-8">
</head>
<body>
  <div id="container"></div>
</body>
</html>

【问题讨论】：

请提供您的一些代码或您的问题的最小表示
您可以手动将节点的位置移动到所需的数量，以将节点保持在屏幕的预期位置。

标签： javascript html5-canvas konvajs

【解决方案1】：

好吧，基本上必须按照 lavrton 说的做，将形状放在一个组中（位置正确），然后在组内旋转和偏移形状。

const stage = new Konva.Stage({
  container: 'container',
  width: 300,
  height: 700
});

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

const rotatePoint = ({ x, y }, rad) => {
  const rcos = Math.cos(rad);
  const rsin = Math.sin(rad);
  return { x: x * rcos - y * rsin, y: y * rcos + x * rsin };
}

// will work for shapes with top-left origin, like rectangle
const rotateAroundCenter = (node, rotation) => {
  //current rotation origin (0, 0) relative to desired origin - center (node.width()/2, node.height()/2)
  const topLeft = { x: -node.width() / 2, y: -node.height() / 2 };
  const current = rotatePoint(topLeft, Konva.getAngle(node.rotation()));
  const rotated = rotatePoint(topLeft, Konva.getAngle(rotation));
  const dx = rotated.x - current.x,
        dy = rotated.y - current.y;
  
  const r = Math.floor(rotation / 90) % 4;  
  switch(r){
    case 1:
    case 3:
      node.x(node.x() + dx + node.height()/2);
      node.y(node.y() + dy + node.width()/2);
      break;
    case 2:
    default: 
      node.x(node.x() + dx + node.width()/2);
      node.y(node.y() + dy + node.height()/2);
      break;
  }

  node.rotation(rotation);
  
  return node;
}

let x = 200, y = 250, width = 30, height = 75, text = "? ? ? ? ?", opacity = 0.4;

drawShapes = (x, y, width, height, rotation) => {  
  layer.add(new Konva.Text({x:0, y, fill: 'black', text: (rotation+"°").padStart(5,"_")}));
  
  layer.add(new Konva.Rect({x, y, width, height, fill: 'black', rotation}));
  layer.add(new Konva.Text({x, y, width, height, fill: 'white', rotation, text}));

  const group = new Konva.Group({ x, y,/* clip:{x:0,y:0,width:200,height:200}*/})
  
  group.add(rotateAroundCenter(new Konva.Rect({x:-width/2,y:-height/2, width, height,fill: 'grey', opacity}), rotation));
  group.add(rotateAroundCenter(new Konva.Text({x:-width/2,y:-height/2, width, height,fill: 'black', text}), rotation));
  layer.add(group, new Konva.Circle({x, y, radius: 2, fill: 'black'}));
}
drawShapes(x, 50, width, height,   0);
drawShapes(x, 200, width, height,  90);
drawShapes(x, 350, width, height, 180);
drawShapes(x, 500, width, height, 270);


layer.draw();

<!DOCTYPE html>
<html>
<head>
<meta name="description" content="KonvaJS Template">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/konva/4.2.0/konva.min.js"></script>
  <meta charset="utf-8">
</head>
<body>
  <div id="container" style="height:700px"></div>
</body>
</html>

【讨论】：