The Gray Owl Thumbnail resize plugin was specifically designed for developers and general users. the plugin allows you to conveniently edit the size and composition of thumbnails.
The plugin has a convenient editor for working with all registered thumbnail ( add_image_size () ). the editor works with three types of images (.jpg .png .gif), in the editor it is possible in some cases to change the background color, create a transparent background and many other settings.
Our team is working on appropriate additional options that will appear with subsequent updates.