HTML5 Canvas 图形调整尺寸和变换限制

要限制或更改调整尺寸和变换的行为，可以使用 boundBoxFunc 属性。 它的工作方式与 dragBoundFunc 类似。

操作说明：尝试调整图形尺寸。你会看到其宽度限制为 200。

示例将新的包围盒收敛（clamp）到限制值，而不是直接拒绝它。如果在超出限制时简单地 return oldBox，快速移动鼠标会在一次事件中越过边界，图形就会卡在限制值之下。在 oldBox 和 newBox 之间插值可以精确地停在限制值上，并且对每个锚点都能保持图形另一侧固定不动。

你还可以单独控制每个锚点的移动。请参阅 调整尺寸吸附示例。

Vanilla

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);

const rect = new Konva.Rect({
x: 50,
y: 50,
width: 100,
height: 100,
fill: 'yellow',
stroke: 'black',
draggable: true,
});
layer.add(rect);

const tr = new Konva.Transformer({
nodes: [rect],
boundBoxFunc: (oldBox, newBox) => {
// limit resize to a maximum width of 200.
// clamp the box between oldBox and newBox instead of
// rejecting it, so a fast drag still lands exactly on the limit
if (newBox.width > 200) {
const t = (200 - oldBox.width) / (newBox.width - oldBox.width);
return {
x: oldBox.x + t * (newBox.x - oldBox.x),
y: oldBox.y + t * (newBox.y - oldBox.y),
width: 200,
height: oldBox.height + t * (newBox.height - oldBox.height),
rotation: newBox.rotation,
};
}
return newBox;
},
});
layer.add(tr);

React

import { Stage, Layer, Rect, Transformer } from 'react-konva';
import { useRef, useEffect, useState } from 'react';

const App = () => {
  const [rectPosition, setRectPosition] = useState({ x: 50, y: 50 });
  const rectRef = useRef();
  const trRef = useRef();

  useEffect(() => {
    trRef.current.nodes([rectRef.current]);
  }, []);

  return (
    <Stage width={window.innerWidth} height={window.innerHeight}>
      <Layer>
        <Rect
          x={rectPosition.x}
          y={rectPosition.y}
          width={100}
          height={100}
          fill="yellow"
          stroke="black"
          draggable
          ref={rectRef}
          onDragEnd={(e) => setRectPosition(e.target.position())}
          onTransformEnd={(e) => setRectPosition(e.target.position())}
        />
        <Transformer
          ref={trRef}
          boundBoxFunc={(oldBox, newBox) => {
            // limit resize to a maximum width of 200.
            // clamp the box between oldBox and newBox instead of
            // rejecting it, so a fast drag still lands exactly on the limit
            if (newBox.width > 200) {
              const t = (200 - oldBox.width) / (newBox.width - oldBox.width);
              return {
                x: oldBox.x + t * (newBox.x - oldBox.x),
                y: oldBox.y + t * (newBox.y - oldBox.y),
                width: 200,
                height: oldBox.height + t * (newBox.height - oldBox.height),
                rotation: newBox.rotation,
              };
            }
            return newBox;
          }}
        />
      </Layer>
    </Stage>
  );
};

export default App;

Vue

<template>
  <v-stage :config="stageSize">
    <v-layer>
      <v-rect
        :config="rectConfig"
        ref="rectRef"
      />
      <v-transformer
        :config="transformerConfig"
        ref="transformerRef"
      />
    </v-layer>
  </v-stage>
</template>

<script setup>
import { ref, onMounted } from 'vue';

const stageSize = {
  width: window.innerWidth,
  height: window.innerHeight
};

const rectConfig = {
  x: 50,
  y: 50,
  width: 100,
  height: 100,
  fill: 'yellow',
  stroke: 'black',
  draggable: true
};

const transformerConfig = {
  boundBoxFunc: (oldBox, newBox) => {
    // limit resize to a maximum width of 200.
    // clamp the box between oldBox and newBox instead of
    // rejecting it, so a fast drag still lands exactly on the limit
    if (newBox.width > 200) {
      const t = (200 - oldBox.width) / (newBox.width - oldBox.width);
      return {
        x: oldBox.x + t * (newBox.x - oldBox.x),
        y: oldBox.y + t * (newBox.y - oldBox.y),
        width: 200,
        height: oldBox.height + t * (newBox.height - oldBox.height),
        rotation: newBox.rotation,
      };
    }
    return newBox;
  }
};

const rectRef = ref(null);
const transformerRef = ref(null);

onMounted(() => {
  transformerRef.value.getNode().nodes([rectRef.value.getNode()]);
});
</script>