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.

mores

This plugin is basically just a little improvement of <a href="https://wordpress.org/extend/plugins/resize-at-upload/" title="Resize-At-Upload" rel="ugc">Resize-At-Upload</a>, a fabulous plugin by A. Huizinga.
The plugin will automatically resize an image upon upload, depending on the maximum width and height that you define. Gone are the days when you, or your client, will ruin a site’s layout by uploading a huge file with 25 megapixels. 
Be advised: there is no backup, no copy of the originally uploaded image.
The plugin uses a class originally from Jacob Wyke (www.redvodkajelly.com).

Resize at Upload Plus

Automatically resize (i.e. scale down) images after uploading. Save disk space and preserve your layout

Resize Images In Posts vs Resize at Upload Plus