This plugin allow create custom image sizes for your site. Override your theme sizes directly on the media option page.
You can regenerate all the sizes you have just created and choose which one you wanted to regenerate.
You can now get all the code to copy and paste to your function theme file.
Now you can use the generated sizes directly into your posts and insert images at the right size !
Now you choose if you want display the size in the post insert image.
Now you can regenerate the images one by one in the ‘Medias’ general pane.
Now you can regenerate the images by bulk action in the ‘Medias’ general pane.
Now you can regenerate the image sizes on single attachment edit page.
I have added a timer so when you regeneration your thumbnails, you can know approximately when the regeneration will be ended.
Contribute on https://github.com/Rahe/Simple-image-sizes