如何创建一个函数与一个参数，将模糊的图像在php

How to create a function with one paramter that will blur an image in php

我使用图像魔术php(函数Imagick::blurImage)，它有2个参数半径和sigma。我该如何根据模糊的百分比来计算这两个参数呢?

function blur($image, $percent) {
   // how to calculate sigma and radius
}
$image = new Imagick($_GET['image']);
blur($image, $_GET['blur']);
echo $image;

function blur($image, $percent) {
   $blur = $percent*20/100;
   $image->gaussianBlurImage($blur, $blur);
}