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.

andersthorborg

ACF image crop is an extended version of the native Image-field in ACF. 
The field gives the developer/administrator the option to predefine a size for the image, which the user is prompted to crop on the various edit screens. This solves the common issue of images being cropped inappropriately by the automated center-crop, that wordpress performs.
The plugin supports the defined image sizes as well as a custom option, enabling the developer to specify the dimensions from within the field edit screen.
The field can be configured to enforce a hard crop or a minimal-dimension-based crop. The hard crop will lock the aspect ratio of the crop where as the minimal-dimension-based crop will not allow the user to crop the image below the specified dimensions.
This plugin diverts from plugins like <a href="https://wordpress.org/plugins/manual-image-crop/">Manual Image Crop</a> in that when the user crops an image, a new attachment is generated, so that the relevant crop only applies in the context it is edited. It also keeps the user from dealing with the concept of various image sizes.
As of version 1.0 the field can be configured to either create the cropped image as a media-item (the default behavior) or simply create it and refer directly to the file without adding it to the media library. This will prevent the media library from being cluttered with several cropped versions of the same image. When this option is selected the only available return type for the field is URL.
<h4>Compatibility</h4>
This add-on will work with:
<ul>
<li>version 4 and up</li>
</ul>

Advanced Custom Fields: Image Crop Add-on

So this plugin rocks but it seem to have a bug (might have been fixed), the new image that is generated from the cropping of the image is bigger in files size than the original. 

For example I would crop say 1000x1000px (size 30kbs) image and crop it down too 500x500px and the files size would be 60kbs. Ever time i would re-crop the image it would increase in file size.

Anyway great plugin



Love great plugin but ..

An image field making it possible/required for the user to crop the selected image to the specified image size or dimensions

Picture grabber, resizer and cropper vs Advanced Custom Fields: Image Crop Add-on