not sure where but I came across as image hosting site that allows you to upload your image in a large format or to sharpen it.
I personally do not recall or know of any functions of GD library to sharpen image which might just be a different word for quality being up-ed.
If some one knows of a function to sharpen images please tell me since personally I am not aware of such functions neither in Image Magic and/or GD Library.
- Thanks in advance
You'd use imageconvolution() with a matrix that corresponds to a sharpen filter. Details in this comment on the PHP site: http://php.net/manual/en/ref.image.php#56144
You can use imageconvolution in GD with a sharpen mask. A good example is at http://adamhopkinson.co.uk/blog/2010/08/26/sharpen-an-image-using-php-and-gd/
I haven't tried it, but this looks like what you're looking for, as far as ImageMagick goes.
In GD library of php having a file with path
lib/PHPImageWorkshop/Core/ImageWorkshopLayer.php
Please go to save public function and you can change the imageQuality upto 100. make sure which type of image you want to create. Hope this will help you.
来源：https://stackoverflow.com/questions/6141713/sharpen-image-quality-with-php-gd-library