vuepress-theme-plume/docs/snippet/echarts-8.snippet.md

::: echarts
```js
/* eslint-disable */

function getNoiseHelper() {
  class Grad {
    constructor(x, y, z) {
      this.x = x
      this.y = y
      this.z = z
    }

    dot2(x, y) {
      return this.x * x + this.y * y
    }

    dot3(x, y, z) {
      return this.x * x + this.y * y + this.z * z
    }
  }
  const grad3 = [
    new Grad(1, 1, 0),
    new Grad(-1, 1, 0),
    new Grad(1, -1, 0),
    new Grad(-1, -1, 0),
    new Grad(1, 0, 1),
    new Grad(-1, 0, 1),
    new Grad(1, 0, -1),
    new Grad(-1, 0, -1),
    new Grad(0, 1, 1),
    new Grad(0, -1, 1),
    new Grad(0, 1, -1),
    new Grad(0, -1, -1),
  ]
  const p = [
    151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140,
    36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148, 247, 120,
    234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
    88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71,
    134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133,
    230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54, 65, 25, 63, 161,
    1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196, 135, 130,
    116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250,
    124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227,
    47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213, 119, 248, 152, 2, 44,
    154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9, 129, 22, 39, 253, 19, 98,
    108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228, 251, 34,
    242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14,
    239, 107, 49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121,
    50, 45, 127, 4, 150, 254, 138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243,
    141, 128, 195, 78, 66, 215, 61, 156, 180,
  ]
  // To remove the need for index wrapping, double the permutation table length
  const perm = Array.from({ length: 512 })
  const gradP = Array.from({ length: 512 })
  // This isn't a very good seeding function, but it works ok. It supports 2^16
  // different seed values. Write something better if you need more seeds.
  function seed(seed) {
    if (seed > 0 && seed < 1) {
      // Scale the seed out
      seed *= 65536
    }
    seed = Math.floor(seed)
    if (seed < 256)
      seed |= seed << 8

    for (let i = 0; i < 256; i++) {
      let v
      if (i & 1)
        v = p[i] ^ (seed & 255)
      else
        v = p[i] ^ ((seed >> 8) & 255)

      perm[i] = perm[i + 256] = v
      gradP[i] = gradP[i + 256] = grad3[v % 12]
    }
  }
  seed(0)
  // ##### Perlin noise stuff
  function fade(t) {
    return t * t * t * (t * (t * 6 - 15) + 10)
  }
  function lerp(a, b, t) {
    return (1 - t) * a + t * b
  }
  // 2D Perlin Noise
  function perlin2(x, y) {
    // Find unit grid cell containing point
    let X = Math.floor(x)
    let Y = Math.floor(y)
    // Get relative xy coordinates of point within that cell
    x = x - X
    y = y - Y
    // Wrap the integer cells at 255 (smaller integer period can be introduced here)
    X = X & 255
    Y = Y & 255
    // Calculate noise contributions from each of the four corners
    const n00 = gradP[X + perm[Y]].dot2(x, y)
    const n01 = gradP[X + perm[Y + 1]].dot2(x, y - 1)
    const n10 = gradP[X + 1 + perm[Y]].dot2(x - 1, y)
    const n11 = gradP[X + 1 + perm[Y + 1]].dot2(x - 1, y - 1)
    // Compute the fade curve value for x
    const u = fade(x)
    // Interpolate the four results
    return lerp(lerp(n00, n10, u), lerp(n01, n11, u), fade(y))
  }
  return {
    seed,
    perlin2,
  }
}

const noise = getNoiseHelper()
const xData = []
const yData = []
noise.seed(Math.random())

const data = []
for (let i = 0; i <= 200; i++) {
  for (let j = 0; j <= 100; j++)
    data.push([i, j, noise.perlin2(i / 40, j / 20) + 0.5])

  xData.push(i)
}
for (let j = 0; j < 100; j++)
  yData.push(j)

option = {
  tooltip: {},
  xAxis: {
    type: 'category',
    data: xData,
  },
  yAxis: {
    type: 'category',
    data: yData,
  },
  visualMap: {
    min: 0,
    max: 1,
    calculable: true,
    realtime: false,
    inRange: {
      color: [
        '#313695',
        '#4575b4',
        '#74add1',
        '#abd9e9',
        '#e0f3f8',
        '#ffffbf',
        '#fee090',
        '#fdae61',
        '#f46d43',
        '#d73027',
        '#a50026',
      ],
    },
  },
  series: [
    {
      name: 'Gaussian',
      type: 'heatmap',
      data,
      emphasis: {
        itemStyle: {
          borderColor: '#333',
          borderWidth: 1,
        },
      },
      progressive: 1000,
      animation: false,
    },
  ],
}

const height = 500
```
:::