zlabs

Picgrab is a plugin that download, resize and crop an image on the fly. 
Simply add the “resize” attribute in the img tag you want to grab & resize on your post.
E.g. 
<img src=”http://farm4.static.flickr.com/3532/3243887563_700849f242.jpg” resize=”402×200c;66y” /> 
Once activated, the plugin replaces the attribute “src” on img tags containing the “resize” attribute with something like:
http://yoursite/wp-content/plugins/picgrab/resize.php?url=<coded characters>&size=<coded characters> 
and removes the “resize” attribute.
The resize.php script included with plugin does the work to grab, crop and resize the image. 
It also manages the cache. 
The resize attribute format is:
[(x0,y0,xs,ys)]<xd>x|x<yd>|<xd>x<yd>[c[<crop>]][;<cachetime>]
e.g. 100x, x200, 100×50, 100×200c50, 100×200c
Refer to <a href="http://fabrizio.zellini.org/resize-e-crop-immagini-in-php" title="Crop / Resize script" rel="nofollow ugc">This post</a> for more informations on resizer syntax.
PicGrab require Php version >=8, gd and curl libraries.

Picture grabber, resizer and cropper

Picgrab is a plugin that download, resize and crop an image on the fly. It also stores resized and cropped images in local cache.

Human Made

Joe Hoyle

Matthew Haines-Young

tcrsavage

Tom Willmot

WP Thumb is a simple plugin that seamlessly integrates with the WordPress image functions. You can specify height, width and crop values, and an image will be generated, which is then cached for future use.
<h4>Features</h4>
<ul>
<li>Automatic images resizing, cropping and caching.</li>
<li>Ideal for when you want to change the dimensions of default image sizes.</li>
<li>Can extend using filters to make use of any of the phpThumb Library functions by manipulating the image object.</li>
</ul>
<h3>Contribution guidelines</h3>
see https://github.com/humanmade/WPThumb/blob/master/CONTRIBUTING.md

WPThumb

An on-demand image generation replacement for WordPress' image resizing.

Picture grabber, resizer and cropper vs WPThumb