No thumbnails in your wordpress? Read on…
I noticed last night that my wordpress is not generating thumbnails from uploaded images like it’s suppose to. You’ll noticed that the size options (thumbnail, medium, large) are all disabled except for the full size.
After doing a lot of searching, I finally found out that in order for wordpress to generate thumbnails “by default”, you need to have GD library support for your php. It would have been nice if wordpress had documented that better.
The only reference I found was this:
http://wordpress.org/support/topic/235625
To be clear, wordpress does not generate thumbnails by default unless your php instance has GD support.
Install php gd library
For me, installing GD library was easy:
# yum install php-gd
Check for gd
To check if you have GD loaded in php:
# php -m [PHP Modules] bz2 calendar ctype curl date dbase exif ftp gd gettext gmp hash iconv
Thanks for the tip. Adding the php-gd package to CentOS is a snap.
So, it appears that WordPress creates the various image sizes upon upload; the image size options don’t appear until re-adding them. Is that right?
That’s correct. The various image sizes are generated when you upload. So if you did not have php-gd installed when you uploaded pics the first time, then you will have to re-upload them.
To confirm, you can look in your uploads directory. There should be a file for each size that was generated.
E.g.
viking_full-112×150.jpg
viking_full-225×300.jpg
viking_full.jpg
[...] I just discovered why Wordpress was not resizing my image uploads. It turns out that Wordpress requires the php-gd library to do this, but as this gentleman points out, Wordpress does not document this anywhere. [...]