canvas Gaussian blur effect

// imgData：canvas 的 getImageData 方法返回值
// radius：模糊的半径
function gaussBlur(imgData, radius) {
    

  radius *= 3;    //不知为什么,My blur radius is css中 filter:bulr The effect is the same when the value is tripled.

  //Copy图片内容
  let pixes = new Uint8ClampedArray(imgData.data);
  const width = imgData.width;
  const height = imgData.height;
  let gaussMatrix = [],
    gaussSum,
    x, y,
    r, g, b, a,
    i, j, k,
    w;

  radius = Math.floor(radius);
  const sigma = radius / 3;

  a = 1 / (Math.sqrt(2 * Math.PI) * sigma);
  b = -1 / (2 * sigma * sigma);

  //生成高斯矩阵
  for (i = -radius; i <= radius; i++) {
    
    gaussMatrix.push(a * Math.exp(b * i * i));
  }

  //x 方向一维高斯运算
  for (y = 0; y < height; y++) {
    
    for (x = 0; x < width; x++) {
    
      r = g = b = a = gaussSum = 0;
      for (j = -radius; j <= radius; j++) {
    
        k = x + j;
        if (k >= 0 && k < width) {
    
          i = (y * width + k) * 4;
          w = gaussMatrix[j + radius];

          r += pixes[i] * w;
          g += pixes[i + 1] * w;
          b += pixes[i + 2] * w;
          a += pixes[i + 3] * w;

          gaussSum += w;
        }
      }

      i = (y * width + x) * 4;
      //计算加权均值
      imgData.data.set([r, g, b, a].map(v => v / gaussSum), i);
    }
  }

  pixes.set(imgData.data);

  //y 方向一维高斯运算
  for (x = 0; x < width; x++) {
    
    for (y = 0; y < height; y++) {
    
      r = g = b = a = gaussSum = 0;
      for (j = -radius; j <= radius; j++) {
    
        k = y + j;

        if (k >= 0 && k < height) {
    
          i = (k * width + x) * 4;
          w = gaussMatrix[j + radius];

          r += pixes[i] * w;
          g += pixes[i + 1] * w;
          b += pixes[i + 2] * w;
          a += pixes[i + 3] * w;

          gaussSum += w;
        }
      }
      i = (y * width + x) * 4;
      imgData.data.set([r, g, b, a].map(v => v / gaussSum), i);
    }
  }

  return imgData;
};

详细内容请看下文：
本文转载：https://blog.csdn.net/xuanhun521/article/details/109362541