Tor N. Johnson

The traditional wordpress image resizing engine will resize images to fit within the specified size but not preserve the destination pixel dimensions OR will crop the image. This plugin gives a third alternative – the image will be reduced to fit within the specified size and then the canvas extended to preserve the destination pixel dimensions. The canvas will then be filled in based on a sampling of the colors in the four corners of the image.
<h3>Requirements</h3>
This plugin requires that either ImageMagick or GD be installed on the server.

TileCrop

Extends the resize/crop function to allow images to be matted and enforce aspect ratios.

Nicolas Juen

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. 
I have improved the php and javascript, you can know if the image have been regenerated or not or if there is an error and which one.
Contribute on https://github.com/Rahe/Simple-image-sizes

Simple Image Sizes

Donate link: http://www.beapi.fr/donate/ Tags: images, image, custom sizes, custom images, thumbnail regenerate, thumbnail, regenerate, cropping Requi …

TileCrop vs Simple Image Sizes