Speak of, the colorful theme templates and omnipotent plugins is the most attractive for us, WordPress support automatically uploading pictures for users to generate thumbnails. A variety of multiple thumbnails enable us to maximize to optimize the theme visual effects.
Generally we install the theme, automatically generated thumbnail size according to the needs, so that the theme automatically calls, or we manually insert the images into the page. But when we change a new theme, the problem comes, the new theme probably needs different size of thumbnail size from prvious theme. At this time, we have a variety of ways to regenerate the Thumbnail images. But for me, the most simple, the most thorough, the most perfect way is to regenerate all of thumbnail images of the whole website.
So I found the following 2 plugins:
If you search in internet, you will find that these two plugins frequently appear in the author recommendation lists. only used Regenerate Thumbnails because it was in self built server, I set the PHP execution time limit very long, and the number of pictures on the site is not so much, so the process of regeneration thumbnails is successful. And for those users with too much images in the site, Thumbnail Rebuild AJAX may be a better choice. Read the introduction from Thumbnail Rebuild AJAX, it can solve the problem of the massive picture execution time exceeds PHP setting.
When you have a lot of full-size photos, the script on the server side takes a long time to run. Unfortunately the time a script is allowed to run is limited, which sets an upper limit to the number of thumbnails you can regenerate. This number depends on the server configuration and the computing power your server has available. When you get over this limit, you won’t be able to rebuild your thumbnails. AJAX Thumbnail Rebuild allows you to rebuild all thumbnails at once without script timeouts on your server.