如何在 Canvas 上播放 GIF 动画

如何在 Canvas 上显示 GIF 动画？

无法将 GIF 图像直接插入 Canvas。但是，可以使用外部库解析 GIF，然后将其作为 Konva.Image 图形绘制到图层中。

此示例使用 gifler 解析和绘制 GIF。也可以使用其他库。

Vanilla

import Konva from 'konva';

// Load gifler library
const script = document.createElement('script');
script.src = 'https://unpkg.com/[email protected]/gifler.min.js';
document.head.appendChild(script);

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

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

const canvas = document.createElement('canvas');

// use external library to parse and draw gif animation
function onDrawFrame(ctx, frame) {
  // update canvas size
  canvas.width = frame.width;
  canvas.height = frame.height;
  // update canvas that we are using for Konva.Image
  ctx.drawImage(frame.buffer, 0, 0);
  // redraw the layer
  layer.draw();
}

script.onload = () => {
  gifler('https://konvajs.org/assets/yoda.gif').frames(canvas, onDrawFrame);
};

// draw resulted canvas into the stage as Konva.Image
const image = new Konva.Image({
  image: canvas,
});
layer.add(image);

React

import React from 'react';
import { Stage, Layer, Image } from 'react-konva';

const GifImage = () => {
  const imageRef = React.useRef(null);
  const canvasRef = React.useRef(document.createElement('canvas'));

  React.useEffect(() => {
    // Load gifler library
    const script = document.createElement('script');
    script.src = 'https://unpkg.com/[email protected]/gifler.min.js';
    
    script.onload = () => {
      // use external library to parse and draw gif animation
      function onDrawFrame(ctx, frame) {
        // update canvas size
        canvasRef.current.width = frame.width;
        canvasRef.current.height = frame.height;
        // update canvas that we are using for Konva.Image
        ctx.drawImage(frame.buffer, 0, 0);
        // update Konva.Image
        imageRef.current?.getLayer()?.batchDraw();
      }

      gifler('https://konvajs.org/assets/yoda.gif').frames(canvasRef.current, onDrawFrame);
    };

    document.head.appendChild(script);
    return () => script.remove();
  }, []);

  return (
    <Image
      ref={imageRef}
      image={canvasRef.current}
    />
  );
};

const App = () => {
  return (
    <Stage width={window.innerWidth} height={window.innerHeight}>
      <Layer>
        <GifImage />
      </Layer>
    </Stage>
  );
};

export default App;

Vue

<template>
  <v-stage :config="stageConfig">
    <v-layer>
      <v-image
        :config="{ image: canvas }"
        ref="imageRef"
      />
    </v-layer>
  </v-stage>
</template>

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

const canvas = document.createElement('canvas');
const imageRef = ref(null);

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

onMounted(() => {
  // Load gifler library
  const script = document.createElement('script');
  script.src = 'https://unpkg.com/[email protected]/gifler.min.js';
  
  script.onload = () => {
    // use external library to parse and draw gif animation
    function onDrawFrame(ctx, frame) {
      // update canvas size
      canvas.width = frame.width;
      canvas.height = frame.height;
      // update canvas that we are using for Konva.Image
      ctx.drawImage(frame.buffer, 0, 0);
      // update Konva.Image
      imageRef.value.getNode().getLayer().batchDraw();
    }

    gifler('https://konvajs.org/assets/yoda.gif').frames(canvas, onDrawFrame);
  };

  document.head.appendChild(script);
  
  return () => script.remove();
});
</script>

操作说明：此示例展示如何使用 gifler 库在 Canvas 上渲染 GIF 动画。示例解析 GIF 并将每一帧绘制到一个 Canvas 上，然后将该 Canvas 用作 Konva.Image 图形的图像源。