输出图象到浏览器或文件。

imageavif(
    GdImage $image,
    resource|string|null $file = null,
    int $quality = -1,
    int $speed = -1
): bool

Outputs or saves a AVIF Raster image from the given image.

image: 由图象创建函数(例如imagecreatetruecolor())返回的图象资源。
file: 文件保存的路径，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 30 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.

成功时返回 true，或者在失败时返回 false。

警告

如果 libgd 输出图像失败，函数会返回 true。