相对于指针位置缩放舞台

此示例展示如何实现相对于鼠标指针位置的缩放。这种方式以鼠标指针为中心缩放内容，可以提供更自然的缩放体验。

操作说明： 使用鼠标滚轮或触控板放大和缩小。观察内容如何以指针位置为中心缩放，而不是以舞台中心缩放。

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 circle = new Konva.Circle({
  x: stage.width() / 2,
  y: stage.height() / 2,
  radius: 50,
  fill: 'green',
});
layer.add(circle);

const scaleBy = 1.01;
stage.on('wheel', (e) => {
  // stop default scrolling
  e.evt.preventDefault();

  const oldScale = stage.scaleX();
  const pointer = stage.getPointerPosition();

  const mousePointTo = {
    x: (pointer.x - stage.x()) / oldScale,
    y: (pointer.y - stage.y()) / oldScale,
  };

  // how to scale? Zoom in? Or zoom out?
  let direction = e.evt.deltaY > 0 ? 1 : -1;

  // when we zoom on trackpad, e.evt.ctrlKey is true
  // in that case lets revert direction
  if (e.evt.ctrlKey) {
    direction = -direction;
  }

  const newScale = direction > 0 ? oldScale * scaleBy : oldScale / scaleBy;

  stage.scale({ x: newScale, y: newScale });

  const newPos = {
    x: pointer.x - mousePointTo.x * newScale,
    y: pointer.y - mousePointTo.y * newScale,
  };
  stage.position(newPos);
});

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React

import { Stage, Layer, Circle } from 'react-konva';
import { useRef } from 'react';

const App = () => {
  const width = window.innerWidth;
  const height = window.innerHeight;
  const stageRef = useRef(null);

  const handleWheel = (e) => {
    e.evt.preventDefault();

    const stage = stageRef.current;
    const oldScale = stage.scaleX();
    const pointer = stage.getPointerPosition();

    const mousePointTo = {
      x: (pointer.x - stage.x()) / oldScale,
      y: (pointer.y - stage.y()) / oldScale,
    };

    // how to scale? Zoom in? Or zoom out?
    let direction = e.evt.deltaY > 0 ? 1 : -1;

    // when we zoom on trackpad, e.evt.ctrlKey is true
    // in that case lets revert direction
    if (e.evt.ctrlKey) {
      direction = -direction;
    }

    const scaleBy = 1.01;
    const newScale = direction > 0 ? oldScale * scaleBy : oldScale / scaleBy;

    stage.scale({ x: newScale, y: newScale });

    const newPos = {
      x: pointer.x - mousePointTo.x * newScale,
      y: pointer.y - mousePointTo.y * newScale,
    };
    stage.position(newPos);
  };

  return (
    <Stage
      width={width}
      height={height}
      ref={stageRef}
      onWheel={handleWheel}
    >
      <Layer>
        <Circle
          x={width / 2}
          y={height / 2}
          radius={50}
          fill="green"
        />
      </Layer>
    </Stage>
  );
};

export default App;

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Vue

<template>
  <v-stage
    ref="stageRef"
    :config="stageConfig"
    @wheel="handleWheel"
  >
    <v-layer>
      <v-circle :config="circleConfig" />
    </v-layer>
  </v-stage>
</template>

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

const width = window.innerWidth;
const height = window.innerHeight;
const stageRef = ref(null);

const stageConfig = computed(() => ({
  width,
  height,
}));

const circleConfig = computed(() => ({
  x: width / 2,
  y: height / 2,
  radius: 50,
  fill: 'green',
}));

const handleWheel = (e) => {
  e.evt.preventDefault();

  const stage = stageRef.value.getNode();
  const oldScale = stage.scaleX();
  const pointer = stage.getPointerPosition();

  const mousePointTo = {
    x: (pointer.x - stage.x()) / oldScale,
    y: (pointer.y - stage.y()) / oldScale,
  };

  // how to scale? Zoom in? Or zoom out?
  let direction = e.evt.deltaY > 0 ? 1 : -1;

  // when we zoom on trackpad, e.evt.ctrlKey is true
  // in that case lets revert direction
  if (e.evt.ctrlKey) {
    direction = -direction;
  }

  const scaleBy = 1.01;
  const newScale = direction > 0 ? oldScale * scaleBy : oldScale / scaleBy;

  stage.scale({ x: newScale, y: newScale });

  const newPos = {
    x: pointer.x - mousePointTo.x * newScale,
    y: pointer.y - mousePointTo.y * newScale,
  };
  stage.position(newPos);
};
</script>

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