Creating THE HIGHEST QUALITY thumbnails with PHP?

[brianb]

Hello people,

With the implementation of GD 2 in the latest version of PHP, weren't there supposed to be some new functions that creat better JPG thumbnails?

I have a script right now that looks like this:

//if a file was uploaded
$file_name = "$ID.jpg";
if( @copy($file, "mypath/$file_name") )
{  

   $iname="$file";
   $x=60;
   $y=87;
   $srcimage         = ImageCreateFromJPEG ($iname);
   $newimage        = imagecreate ($x, $y);
   imagecopyresized ($newimage, $srcimage, 0, 0, 0, 0, $x, $y, imagesx($srcimage), imagesy($srcimage));
   imagejpeg($newimage,"mypath/$ID.jpg");

   //delete the temporary uploaded image
   unlink($file);
}

Now, can someone fill me in on the new functions, or help me make my code a little tighter to get "unchunky", pixelated thumbs? I want some smooth looking, hi-rez thumbs.

Any, and all help is much appreciated!!!

[Mordecai]

I don't use GD 2, but I may be able to help.
First off, use imagecreatetruecolor() to make a truecolor image. Then, use the quality parameter of imagejpeg(), like so:
$im = imagecreatetruecolor(100,100);
imagejpeg($im,"",100);

But jpegs aren't your best choice if you want quality.

[brianb]

Cool. That helps.

What is the best choice for quality? PNG's? GIF's?

See, I'm uploading a perfect image into one directory, then from that image I want to create a nice looking JPG thumb. That's my scenario.

Isn't there some parameter for anti-aliasing etc?

Hmmm.......please reply!

[Mordecai]

PNGs are perfect quality, but 256 colours through GD. I would think they would be fine for thumbnails, though. You can't specify quality on them, as you can with JPEGs.

[spirp]

There's a good reason why you can't specify the quality on PNGs, and that's because the compression used in PNGs (LZ77) isn't destructive as it is in JPG..

Anyway.. There's a few tricks one cuold use to generate higher quality thumbnails.. Let's asume that the image you want to create a thumbnail from is a 1024x768 jpeg:

1. Re-scale the image to, let's say 600x450

2. Crop this image to 340x255, but don't just take the middle part of the image, but move the crop-mask slightly off centre

3. Rescale this image you preferred size (say, 100x75)
   [/list=1]

   An important aspect of creating thumbnails is to keep the aspect ratio of the image. That is, do not re-scale a 1000x500 to a 100x200 image. But, of course, that's quite obvious.. 🙂

   This method usually works out just fine when rescaling high detail images such as screen shots.. You might need to modify the values above by trial and error in photoshop or so..

   Good luck,
   Olle