yoshi

Multifile Upload plugin adds some features to the WordPress’ default upload interface. You will be able to upload more than one file at a time. You can also resize the original image by specifying the size and change the thumbnail size when uploading.

Multifile Upload

This plugin allows WP's upload interface to handle multiple files at a time. User can also change the original and thumbnail image sizes.

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

Multifile Upload vs Resize at Upload Plus