image output: throw ValueError on out-of-bounds qualities

[steffdimitrov]

Description

The following code:

<?php
ob_start();
imagepng($resource, null, 98);
$contents = ob_get_clean();
ob_end_flush();

var_dump($contents);

Resulted in this output:

string(0);

But I expected this output instead:

ERROR

or:

$content = <<<Binary data here >>>

Tested on php 7.3 but I think it is also applicable for other version using gd.

PHP Version

PHP 7.3.33

Operating System

Ubuntu 20.04

[cmb69]

The $quality must be in range 0 to 9. If you pass 98, you get a warning: "imagepng(): gd-png error: compression level must be 0 through 9", and the function returs false, which is converted to an empty string.

[steffdimitrov]

Yes, I saw that my warnings/notices were turned off. But still, IMO passing data outside wanted range must be an error. Also, imagejpeg wants number between 0 and 100, imagepng wants number between 0 and 9, imagegif doesn't have quality parameter...

[cmb69]

It might make sense to throw a ValueError for out-of-bounds qualitites, but for BC reasons, that would have to wait until PHP 9, and might require an RFC.