Alexandru Vornicescu

This is a WordPress plugin.
If you want to resize images in your posts automatically so the page will load faster and use less bandwidth then this plugin can help you.
To take effect just open a post or page and all images in that post will be resized to a smaller version.
It will replace the URLs of the images that are too big with URLs of the resized images that will fit into the posts.
The plugin will keep the original copy of all image files.
Note: With version 4.3 now you can resize images in Text Widgets.
Note: The filter – “wp_make_content_images_responsive” will be deactivated because with this plugin we will not need anymore.

Resize Images In Posts

This plugin will resize images in your posts.

huiz

The plugin affects the uploaded image while it is uploaded. Straight 
after it is uploaded, it it resized physically to the given width. 
There is no original image left, nor made a backup. Also EXIF infor- 
mation is lost.
A lot of WordPress users or developers who use WordPress as a CMS 
and want to configurate it for easy use, would like to have an option 
to resize uploaded images. Some images come straight from digital cameras 
and exceed 4000 pixels in width. So it would be nice to reduce that to 
the max width you use inside your WordPress theme.
If you want to keep control about perfect sharp and resized images, you 
better use photo editing tools on your computer, not a script like this.
The plugin uses a class originally from Jacob Wyke (www.redvodkajelly.com).

Resize at Upload

This plugin resizes uploaded images to a given width.

Resize Images In Posts vs Resize at Upload