JavaScript+Canvas实现文字粒子流特效

ctx.font = "200px Arial";
ctx.fontWeight = "900";
ctx.textAlign = "left";
ctx.textBaseline = "top";
ctx.fillStyle = "red";
ctx.fillText("稀土掘金", 0, 0);

red=imgData.data[0];
green=imgData.data[1];
blue=imgData.data[2];
alpha=imgData.data[3];

var imgData=context.getImageData(x,y,width,height);

const { width } = ctx.measureText(this.text);

const gap = 4;
for (let i = 0, wl = this.canvas.width * gap; i < length; i += gap) {
    if (data[i + gap - 1]) {
      // 根据透明度判断
      const x = (i % wl) / gap;
      const y = parseInt(i / wl);
      this.textPoints.push([x, y]);
    }
}

let startX;
let startY;
const points = [];
for (let i = 0; i < this.textPoints.length; i++) {
    let point = this.textPoints[i];
    let x = point[0];
    let y = point[1];
    const radius = 5;
    // const radius = Math.random() * 10; // 随机生成粒子宽度
    const color = parseInt(Math.random() * 0xffffff).toString(16); // 随机生成粒子颜色
    const { x: x0, y: y0 } = this.adjustPoint(x, y); // 矫正粒子相对于画布所在位置
    if (i == 0 || ((x - startX) % 10 == 0 && (y - startY) % 10 == 0)) {
      startX = x;
      startY = y;
      const params = { x: x0 + radius, y: y0, radius, color };
      points.push(params);
    }
}

this.points = points.sort((a, b) => (Math.random() > 0.5 ? -1 : 1)); // 随机排序

adjustPoint(x, y) {
  const { width, height } = this.canvasLizi;
  return {
    x: x + (width - this.textWidth) / 2,
    y: y + (height - this.textSize) / 2,
  };
}

for (let item of this.points) {
    let direction;
    const num = Math.random() * 1;
    if (num < 0.25) {
      direction = "left";
      item.initX = 0;
      item.initY = Math.random() * height;
    } else if (num < 0.5) {
      direction = "right";
      item.initX = width;
      item.initY = Math.random() * height;
    } else if (num < 0.75) {
      direction = "top";
      item.initX = Math.random() * width;
      item.initY = 0;
    } else {
      direction = "bottom";
      item.initX = Math.random() * width;
      item.initY = height;
    }
}

animatDot() {
  if (!this.points.find((item) => item.hasOwnProperty("initX"))) {
    // 当不存在运动点时取消动画
    cancelAnimationFrame(this.animatDot.bind(this));
    return;
  }
  this.points.forEach((item) => {
    const offsetX = item.x - item.initX;
    const offsetY = item.y - item.initY;
    if (Math.abs(offsetX) > 0 || Math.abs(offsetY) > 0) {
      const rate = offsetX / 10; // 速率等于坐标差除以10，不断缩小运动距离
      const x = item.initX + rate;
      if (Math.abs(rate) < 1) {
        item.initX = item.x; // 当运动距离小于1时，等于实际坐标
      } else {
        if (offsetX > 0) {
          item.initX = x < item.x ? x : item.x;
        } else {
          item.initX = x > item.x ? x : item.x;
        }
      }
      const k = offsetY / offsetX; // 计算斜率
      const y = k * item.initX;
      if (offsetY > 0) {
        item.initY = y < item.y ? y : item.y;
      } else {
        item.initY = y > item.y ? y : item.y;
      }
    } else {
      delete item.initX; // 当运动点坐标和实际坐标相同时，删除初始坐标
      delete item.initY;
    }
  });
  this.drawPoint(); // 绘制粒子函数
  requestAnimationFrame(this.animatDot.bind(this), 1000 / 60);
}

this.clickRange = 30; // 点击范围
this.spreadRange = 30; // 扩散范围

PBomb() {
  const that = this;
  function animaion(time) {
    that.PBomb();
  }
  if (!this.points.find((item) => item.bomb)) {
    cancelAnimationFrame(animaion); // 停止动画判断
    return;
  }
  const step = 10; // x轴步长，每帧增加或减少的大小
  this.points.forEach((point) => {
    if (point.bomb) {
      if (point.bombX > this.clickPointX) {
        if (point.bombX < point.x + this.spreadRange) {
          point.bombX += step;
        } else {
          point.bomb = false;
        }
      }
      if (point.bombX < this.clickPointX) {
        if (point.bombX > point.x - this.spreadRange) {
          point.bombX -= step;
        } else {
          point.bomb = false;
        }
      }
      const k =
        point.x - this.clickPointX == 0
          ? 1
          : Math.abs(
              (point.y - this.clickPointY) /
                (point.x - this.clickPointX),
            ).toFixed(2); // 计算斜率
      if (point.bombY > this.clickPointY) {
        if (point.bombY < point.y + this.spreadRange) {
          point.bombY += k * step;
        } else {
          point.bomb = false;
        }
      }
      if (point.bombY < this.clickPointY) {
        if (point.bombY > point.y - this.spreadRange) {
          point.bombY -= k * step;
        } else {
          point.bomb = false;
        }
      }
    }
  });
  this.drawPoint();
  setTimeout(() => {
    requestAnimationFrame(animaion);
  }, 1000 / 10);
}