Usage example:
$image = imagecreatefromjpeg('test.jpg');  //read a jpg file
imageavif($image, 'test.avif');  //save an avif file(PHP 8 >= 8.1.0)
imageavif — 输出图象到浏览器或文件。
$image,$file = null,$quality = -1,$speed = -1
   Outputs or saves a AVIF Raster image from the given image.
  
image由图象创建函数(例如imagecreatetruecolor())返回的 GdImage 对象。
file
       文件保存的路径或者已打开的流资源(此方法返回后自动关闭该流资源),如果未设置或为 null,将会直接输出原始图象流。
      
quality
       quality is optional, and ranges from 0 (worst quality, smaller file)
       to 100 (best quality, larger file).
       If -1 is provided, the default value 52 is used.
      
speed
       speed is optional, and ranges from 0 (slow, smaller file)
       to 10 (fast, larger file).
       If -1 is provided, the default value 6 is used.
      
   Throws a ValueError if quality
   or speed is invalid.
  
| 版本 | 说明 | 
|---|---|
| 8.4.0 | Now throws a ValueError if qualityorspeedis invalid. | 
Usage example:
$image = imagecreatefromjpeg('test.jpg');  //read a jpg file
imageavif($image, 'test.avif');  //save an avif file