VRender/abc.html at develop · VisActor/VRender · GitHub

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<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <canvas id="canvas"></canvas>
  </body>
  <script>
    const canvas = document.getElementById('canvas');
    const ctx = canvas.getContext('2d');
    const text = '渐变文字效果';
    let progress = 0;

    // 设置画布尺寸
    canvas.width = 600;
    canvas.height = 200;

    // 创建单个离屏Canvas（同时处理文字和遮罩）
    const maskCanvas = document.createElement('canvas');
    maskCanvas.width = canvas.width;
    maskCanvas.height = canvas.height;
    const maskCtx = maskCanvas.getContext('2d');

    function draw() {
      // 清空所有画布
      ctx.clearRect(0, 0, canvas.width, canvas.height);
      maskCtx.clearRect(0, 0, maskCanvas.width, maskCanvas.height);

      // 主Canvas绘制固定背景
      ctx.fillStyle = 'pink';
      ctx.fillRect(0, 0, canvas.width, canvas.height);

      // 在离屏Canvas完成所有动态效果
      // 步骤1：绘制原始文字
      const gradient = maskCtx.createLinearGradient(0, 0, canvas.width, 0);
      gradient.addColorStop(0, 'red');
      gradient.addColorStop(1, 'blue');
      maskCtx.fillStyle = gradient;
      maskCtx.font = '40px Arial';
      maskCtx.textAlign = 'center';
      maskCtx.textBaseline = 'middle';
      maskCtx.fillText(text, canvas.width / 2, canvas.height / 2);

      // 步骤2：在同一离屏Canvas上创建动态遮罩
      const maskGradient = maskCtx.createLinearGradient(0, 0, canvas.width, 0);
      maskGradient.addColorStop(0, 'rgba(0,0,0,1)');
      maskGradient.addColorStop(Math.min(progress, 1), 'rgba(0,0,0,1)');
      maskGradient.addColorStop(Math.min(progress + 0.1, 1), 'rgba(0,0,0,0)');

      // 使用合成模式裁剪文字
      maskCtx.globalCompositeOperation = 'destination-out';
      maskCtx.fillStyle = maskGradient;
      maskCtx.fillRect(0, 0, maskCanvas.width, maskCanvas.height);
      maskCtx.globalCompositeOperation = 'source-over'; // 恢复默认

      // 将处理后的离屏Canvas绘制到主Canvas
      ctx.drawImage(maskCanvas, 0, 0);

      // 更新动画进度
      if (progress < 1) {
        progress += 0.002;
        requestAnimationFrame(draw);
      }
    }

    draw();
  </script>
</html>