I have used the WordPress plugin Post Thumbnail Editor for multiple websites, as this plugin allows you to resize the image manually instead of automatically. Editors can correct the image size without using external tools. Unfortunately, the author of the plugin seems to be inactive and the compatibility problems are stacking such as WPML not playing nice with the plugin. Since I need a solution for my assignments that works, I decided to search for an alternative for WordPress plugin Post Thumbnail editor.
Instead of using the outdated Post Thumbnail editor, I have found that YoImages is much better compared to Post Thumbanil Editor. The plugin is in active development and looks a bit better than Post Thumbnail Editor.
Please note that I have nothing against the author of Post Thumbnail Editor, I just prefer to have a plugin that is up-to-date.