To desaturate an image means to remove all non-greyscale colours from it, essentially creating a black and white version. To do this you can use the function imagecopymergegray(), which is part of the GD image library. This function is a little difficult to figure out, but what is does is sample one image into another and optionally changing the amount of colours that are kept during the sampling process. The function can be made to sample just a section of the image, or the whole thing. The parameters of the function are as follows.
To debug WordPress many sites will tell you to add the WP_DEBUG setting on its own to your wp-config.php file, but this can be quite harmful as many server configurations will start showing PHP errors and warning messages on your site pages. Most sites will also log any errors to some form or error log, but this isn't always the best place for them to go.
Since WordPress 3.0 there has been a funcion called get_template_part(), which has been used quite a bit in the new Twenty Ten default WordPress theme. This is an evolution of the usual way to include parts of themes by using functions like get_header() to include the header.php file. This function helps code resuse by including the same files multiple files, but also allows child themes to override parent themes.
I know what you are thinking, but this isn't just another WordPress plugin blog post. I am asked every few weeks what WordPress plugins I would recommend, and I always end up giving a disjointed list of some from the top of my head. So instead of doing this I thought it would be a good idea to write down the plugins I use quite a bit and would recommend other to use. I will also try to add any alternatives (if they exist) to plugins I use.
WordCampUK is an informal 2 day conference and barcamp that centers around using, working with and developing in WordPress. This year's WordCampUK was held in Manchester and so being local I could hardly miss the opportunity to attend. It was a great event, with great talks and lots of friendly people who were really enthusiastic about WordPress.