classroom-app/src/views/creation/audioVisualDraw.ts

    /**
     * 音频可视化
     * @param audioDom
     * @param canvasDom
     * @param fftSize  2的幂数，最小为32
     * 注意   由于ios低版本必须在用户操作之后才能初始化 createMediaElementSource 所以必须在用户操作之后初始化
     */
    export default function audioVisualDraw(audioDom: HTMLAudioElement, canvasDom: HTMLCanvasElement, fftSize = 128) {
      type propsType = { canvWidth: number; canvHeight: number; canvFillColor: string; lineColor: string; lineGap: number }
      // canvas
      const canvasCtx = canvasDom.getContext("2d")!
      let { width, height } = canvasDom.getBoundingClientRect()
      // 向上取整，当with为小数或者小于当前dom时候，切换app之后 会出现黑边
      width = Math.ceil(width)
      height = Math.ceil(height)
      canvasDom.width = width
      canvasDom.height = height
      // audio
      //const audioCtx = new AudioContext()
      //const source = audioCtx.createMediaElementSource(audioDom)
      //const analyser = audioCtx.createAnalyser()
      //analyser.fftSize = fftSize
      //source?.connect(analyser)
      //analyser.connect(audioCtx.destination)
      //const dataArray = new Uint8Array(fftSize / 2)
      const draw = (data: Uint8Array, ctx: CanvasRenderingContext2D, { lineGap, canvWidth, canvHeight, canvFillColor, lineColor }: propsType) => {
        if (!ctx) return
        const w = canvWidth
        const h = canvHeight
        fillCanvasBackground(ctx, w, h, canvFillColor)
          // 可视化
        const dataLen = data.length
        let step = (w / 2 - lineGap * dataLen) / dataLen
        step < 1 && (step = 1)
        const midX = w / 2
        const midY = h / 2
        let xLeft = midX
        for (let i = 0; i < dataLen; i++) {
          const value = data[i]
          const percent = value / 255 // 最大值为255
          const barHeight = percent * midY
          canvasCtx.fillStyle = lineColor
          // 中间加间隙
          if (i === 0) {
            xLeft -= lineGap / 2
          }
          canvasCtx.fillRect(xLeft - step, midY - barHeight, step, barHeight)
          canvasCtx.fillRect(xLeft - step, midY, step, barHeight)
          xLeft -= step + lineGap
        }
        let xRight = midX
        for (let i = 0; i < dataLen; i++) {
          const value = data[i]
          const percent = value / 255 // 最大值为255
          const barHeight = percent * midY
          canvasCtx.fillStyle = lineColor
          if (i === 0) {
            xRight += lineGap / 2
          }
          canvasCtx.fillRect(xRight, midY - barHeight, step, barHeight)
          canvasCtx.fillRect(xRight, midY, step, barHeight)
          xRight += step + lineGap
        }
      }
      const fillCanvasBackground = (ctx: CanvasRenderingContext2D, w: number, h: number, colors: string) => {
        ctx.clearRect(0, 0, w, h)
        ctx.fillStyle = colors
        ctx.fillRect(0, 0, w, h)
      }
      const requestAnimationFrameFun = () => {
        // requestAnimationFrame(() => {
        //   //analyser?.getByteFrequencyData(dataArray)
        //   draw(generateMixedData(48), canvasCtx, {
        //     lineGap: 2,
        //     canvWidth: width,
        //     canvHeight: height,
        //     canvFillColor: "transparent",
        //     lineColor: "rgba(255, 255, 255, 0.7)"
        //   })
        //   if (!isPause) {
        //     requestAnimationFrameFun()
        //   }
        // })
        const _time = setInterval(() => {
            if (isPause) {
              clearInterval(_time)
              return
            }
            //analyser?.getByteFrequencyData(dataArray)
            draw(generateMixedData(48), canvasCtx, {
              lineGap: 2,
              canvWidth: width,
              canvHeight: height,
              canvFillColor: "transparent",
              lineColor: "rgba(28,172,241, 0.58)"
            })
        }, 300);
      }
      let isPause = true
      const playVisualDraw = () => {
        //audioCtx.resume()  // 重新更新状态   加了暂停和恢复音频音质发生了变化  所以这里取消了
        isPause = false
        requestAnimationFrameFun()
      }
      const pauseVisualDraw = () => {
        isPause = true
        requestAnimationFrame(()=>{
          canvasCtx.clearRect(0, 0, width, height);
        })
        //audioCtx?.suspend()  // 暂停   加了暂停和恢复音频音质发生了变化  所以这里取消了
        // source?.disconnect()
        // analyser?.disconnect()
      }
      return {
        playVisualDraw,
        pauseVisualDraw
      }
    }

export function generateMixedData(size: number) {
  const dataArray = new Uint8Array(size);
  const baseNoiseAmplitude = 30;
  const minFrequency = 0.01;
  const maxFrequency = 0.2;
  const minAmplitude = 50;
  const maxAmplitude = 150;

  let lastAmplitude = maxAmplitude;  // 初始振幅设置为最大值
  let lastFrequency = minFrequency + Math.random() * (maxFrequency - minFrequency);

  for (let i = 0; i < size; i++) {
      const decayFactor = 1 - (i / size);  // 使振幅随时间递减
      const amplitude = lastAmplitude * decayFactor + (Math.random() - 0.5) * 10;
      const frequency = lastFrequency + (Math.random() - 0.5) * 0.01;
      const wave = amplitude * (0.5 + 0.5 * Math.sin(frequency * i));
      const noise = Math.floor(Math.random() * baseNoiseAmplitude) - baseNoiseAmplitude / 2;
      dataArray[i] = Math.min(255, Math.max(0, Math.floor(wave + noise)));
      lastAmplitude += (amplitude - lastAmplitude) * 0.05;
      lastFrequency += (frequency - lastFrequency) * 0.05;
  }

  return dataArray;
}