Share a piece of program code: Use PHP for image sharpening [absolutely easy to use]

Create a thumbnail program for the album. After uploading an image, you must automatically generate a thumbnail and sharpen it.
I searched the internet and the results were not good at all. Why is the same code in the world?
No way, I had to go to a foreigner to Tao Yi Tao, and found that this is very good. Now I want to share it with you.

<? PHP

Function gdthrowerror ($ message)
{
// Don't throw plain text errors in a function that's supposed to return an image
// As per "the principle of least astonishment": the user is expecting
// A JPEG, and they'll be less astonished to get a jpeg error message
// Than they wocould be if they got plain text. Imagine this was called
// From an image tag, which makes sense, that's how you use images:
// Plain text errors won't even reach most users, they 'd have to copy
// The img src into the address bar. It probably wont 'even occur
// Them, as it's not typically helpful to view the source of an image
// Resource.
$ Font = 2;
// Create a canvas with a bit of padding
$ Errimg = imagecreate (imagefontwidth ($ font) * strlen ($ message) + 20, imagefontheight ($ font) + 10 );
$ BG = imagecolorallocate ($ errimg, 255,255,255 );
$ Textcol = imagecolorallocate ($ errimg, 0, 0 );
Imagestring ($ errimg, 2, 10, 5, $ message, $ textcol );
Header ('content-type: image/JPEG ');
Imagejpeg ($ errimg );
Imagedestroy ($ errimg );
}

Function gdmakeappslooklikecrap ($ target)
{
// Image dimensions are no longer needed (see below), but getimagesize can do some simple Validation
If ($ dims = @ getimagesize ($ target) === false | $ dims ['mime ']! = 'Image/JPEG ')
{
Gdthrowerror ('the file you specified couldn \'t be found or is not a valid JPEG image. Make sure you spelled it correctly and provided the correct path .');
Return (false );
}
// The original function creates a new image and resamples the source to it using the same height and width here.
// I imagine this was to add future resizing functionality but as it is it does nothing but waste resources
$ Image = imagecreatefromjpeg ($ target );
// Don't really know/care what this is. If you're interested SEE http://us2.php.net/imageconvolution
// Try tweaking these three vars for different effects, but there is a sharpening function in the PHP Docs (abve links) and it's not a trivial operation
$ Spnmatrix = array (Array (-1,-1,-1 ,),
Array (-1, 16,-1 ,),
Array (-1,-1,-1 ));
$ Divisor = 8;
$ Offset = 0;
Imageconvolution ($ image, $ spnmatrix, $ divisor, $ offset );
// I like to send headers as late as possible to avoid already sent errors and duplicate header content
Header ('content-type: image/JPEG ');
Imagejpeg ($ image, null, 100 );
Imagedestroy ($ image );
}


// Example call
$ S_image = (isset ($ _ Get ['image'])? $ _ Get ['image']: NULL;

If (preg_match ('/\. (JPG | JPEG) $/I', $ s_image ))
{
Gdmakedomainlooklikecrap ($ s_image );
}
Else
{
Gdthrowerror ('Please specify a jpeg file to sharpen in the form: '. $ _ server ['php _ Self']. '? Image%filename.jpg ');
}
?>