PHP GD library, JPEG PNG lossy compression ratio.

When converting images in JPG (JPEG) and PNG formats using the PHP GD library, the quality of the output image is adjusted as follows:

imagejpeg

0 (lowest quality, smallest size) - 100 (highest quality, largest size).
The default is about 75.

imagepng

0 (no compression) - 9.
Default zlib compression

imagegif

Quality adjustment is not available

imagewbmp

Quality adjustment is not available

GD Graphics Library

https://libgd.github.io

PHP: GD - Manual

https://www.php.net/manual/en/book.image.php

References

PHP: Hypertext Preprocessor
https://www.php.net

Understanding PHP Absolute and Relative Paths
https://www.ppcle.com/post/php-realpath/