class.upload.php
class.upload.php is a powerful and mature PHP class to manage uploaded files, and manipulate images in many ways. The script is available under a GPL license.
class.upload.php is a powerful and mature PHP class to manage uploaded files, and manipulate images in many ways. The script is available under a GPL license.
Basically, the class uses GD functions (and I assume you have GD 2+), which can only do so much.
It could be possible to use another algorithm, but it would be very slow if done in PHP. It is kind of planned in the future to use ImageMagick and/or GD for graphic manipulations, and maybe ImageMagick has a better resizing algorithm.
The sharpening filters will make the image look good, but it is only a trick. The loss of quality will still be there, even if not as noticeable.
So in fact, if you want advanced resizing, with a minimum loss, doing this in PHP might not be the best solution.