Osclass installations on modest hostings tend to provoke problems with PHP memory limit when the users try to upload images with big resolution (like those produced by modern phone devices). In most cases final images on your site won't have more than 640x480 pixels, so normally you have no real need to handle (and maybe permanently store in your server) such big images.
This plugin will resize them to a much more manageable resolution on the client side, before they are sent to your server. This way, to the user uploads are much faster, and to you as admin, it will save a lot of bandwidth and processing power.
By default the plugin sets the maximum resolution for pre-resizing to twice the max value set for "Normal size" in Admin Dashboard / Settings / Media (640x480 by default, so for pre-resizing it would be 1280). Until version 2.0.0 at this resolution some artifacts might be noticed in specififc circumnstances. Now thanks to the introduction of Pica library for better resizing, 1280 is more than enough unless you have special needs and wanted to show really big images to your users.
This plugin should be compatible with any theme that includes Ajax Uploader for images ("Click or drop for upload images"). You'll need to slightly modify your theme, install the plugin and click on Configure (or Plugins / Pre-resize Images / Settings & Help) to change maximum resolution and see instructions.
Note: Currently this plugin replaces Fine Uploader module v. 3.8.0 bundled with Osclass with the latest v. 5.11.10, under MIT license.
Updated Version 2.3.1 attached here. (released 22 / 09 / 2018)