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1. hmccorkle
   Member
   Posted 2 years ago #

   whenever i upload any image and have the thumbnail displayed, the jpeg compression appears to be around 40 or something like that.

   it looks nasty.

   what's the file i can edit in order to adjust the compression?

   i'll post samples on my site: http://grizzlyelephant.com

2. Otto42
   Moderator
   Posted 2 years ago #

   The default is actually 75. The quality difference you see is more likely due to the image resizing algorithm that the PHP/GD library has (which is only bilinear, I think).

   If you look in admin-functions.php, and look for function wp_create_thumbnail, this is where it's making the thumbnail file.

   Scroll down and you'll see this code:
   

   // move the thumbnail to its final destination
   if ( $type[2] == 1 ) {
   	if (!imagegif( $thumbnail, $thumbpath ) ) {
   		$error = __( "Thumbnail path invalid" );
   	}
   }
   elseif ( $type[2] == 2 ) {
   	if (!imagejpeg( $thumbnail, $thumbpath ) ) {
   		$error = __( "Thumbnail path invalid" );
   	}
   }
   elseif ( $type[2] == 3 ) {
   	if (!imagepng( $thumbnail, $thumbpath ) ) {
   		$error = __( "Thumbnail path invalid" );
   	}
   }

   This is where it saves the thumbnail file. Note this line:
   if (!imagejpeg( $thumbnail, $thumbpath ) ) {

   That saves the image to a jpg file if needed. No quality is specified, so it's using the default of 75.

   To change it, edit that line like so:
   if (!imagejpeg( $thumbnail, $thumbpath, 80 ) ) {

   Where 80 is whatever compression you want (0-100).

3. hmccorkle
   Member
   Posted 2 years ago #

   Thank you. So. Much.

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