Last week I finished a project with thousand images (few hundreds megabytes which is basically unimportant) when I suddenly realized that almost each image file is way larger than it is necessary. For example why I should use a 150×150 image as a 50×50 sideshow thumbnail? Plus there was one more resolution for featured images. So I decided to add those two dimensions to optimize page load speed – this was the easy part. Assuming you’ve already faced with this story you might know that adding new image resolution will not generate new images automatically.
At first I’ve tried WordPress’s official plugin database but I was not satisfied with the results. I wrote a little plugin on my own for this little task and that plugin is now available for anyone from the WordPress community. You can do selective or total regenerate for your media library. At this time the plugin works well enough for production use but it is not finished yet. I have some ideas to improve its performance. The biggest issue is the limited server-side capabilities (little RAM, insufficient processing power etc) which can be solved with elapsed time and consumed memory.
You can install ONet Regenerate Thumbnails either via the WordPress.org plugin directory, or by uploading the files to your server. (If you want to contribute the plugin you can find the Git repo at BitBucket).