WordPress Images
Wow, again, where to start... There are so many articles out there on the subject of images and media for WordPress. Most of the top results on Google have good information, are well presented, and even have some tidbits of knowledge for intermediate and advanced users. But there's just so little information that falls into the 'revelation' category. You know, that bit of information that turns on the light bulb in a single instant, changing something from knowledge into working, functional understanding.
Here are some notes on the a fore mentioned 'knowledge epiphany' in the form of notes to myself (hopefully later to be developed into a full blown knowledge base type of article).
WordPress, Images, Efficiency, and Viewing Pleasure
I don't know about you, but I come from a world of high speed internet and large, abundant screen real estate. I sit here writing this today in front of a single 30 inch monitor (along with 5 other 24 inch monitors spread out in an array around said 30 inch monitor). I don't like staring at tiny little images that have foggy detail. You know what I'm talking about. It ranges from that small detail on a product you want to buy and can't see in the image to some historical photograph that's missing the pop and wow factor because someone downsized it so much. Come on! Fast internet, big screens, why not present the biggest image possible to a viewer? Oh, right...
Small Screens
Forgot about all those portable devices that are hooked up to McScrooge 'unlimited service plans' (in that there's no limit to the amount of money they're willing to charge you) from cellular phone companies. For those devices, because of the small screens, they don't need great big pictures. Sometimes that's just the circumstance. Not to get off on a tangent, but it's worth mentioning that I just do not understand why anyone would want to watch, view, read, etc. something on a phone or even a tablet device, if they could do the same thing with a real computer and a great big screen. OK, I get it, sometimes it isn't possible to view something on a great big screen. But it's those times that a big screen is available and someone would still choose a tiny little, super-duper, Retina display from Apple over a cheap 50 inch TV from Wal-Mart. Why? OK, back to the subject.
History
WordPress Thumbnails. Errr, don't you mean 'Alternate Image Sizes'? Well, yes. But WordPress life started out referring to them as 'thumbnails'. A thumbnail being a downsized (as in dimensionally and quality) to a smaller size, which in turn usually represented a link to a larger, full sized image. That's how it began with WordPress. And sort of like Max Headroom, the name just sort of stuck, even though it doesn't refer to the same thing anymore.
Image Management
I do not like the way Apple devices organize files. IE, the 'organization' is done by the software and the user is presented with files, etc. with a big abstraction layer in between. And yes, I know, even a very basic file system / structure from DOS and Linux, as presented to users via a Shell, has an abstraction layer in between the user and what's going on with where the files are on the disk drive. Yes, there's a bunch of abstraction layers. But I am of the opinion (because I have to fix stuff when it doesn't work correctly, or something has to be found, etc.) that there's still a need for a usable File and Directory / Folder structure available to an end user. No so with Apple products.
WordPress is almost like that. And I'm not trying to be dismissive about how they do it. Out of the box, Images are sorted by date, I never liked it, but hey it's better than Apple. The alternative, which is better, but not by much, is to have WordPress store everything in a flat structure. OK, that's fine, but unfortunately, WordPress, along with plugins, themes, etc., also generate additional 'Alternative Image Sizes' (Dimensional
The Notes
Image Services
Watch out for Plugins that are only gateways to a subscription service for compressing images. Really, one's own server can't do that? Well, given the state of some WordPress servers, that's actually understandable, but not for someone who has their own web server (virtual or not). Example (one of many): Imagify.
WebP Files
For well managed JPEG / JPG Files there is an infinitesimally small gain in image size.
Regenerating 'Thumbnails' (AKA Alternate Image Sizes)
By far and away the one I've found to be the best is Real Thumbnail Generator.
Controlling the number of 'Thumbnails' (AKA Alternative Image Sizes)
There are lots of good plugins for managing this. 'Stop Generating Unnecessary Thumbnails' is right at the top. But be warned, weird things can happen. For example, if you see this freaky image size that doesn't seem to make any sense, and has an equally unhelpful name in terms of identifying its origin, watch out. For example, the Astra Theme has an odd image size it wants / needs to display a logo in it's header builder. If that alternate image size isn't created, you won't see anything in the Astra builder utility, just a blank spot. Why doesn't it just use the full size image and downsize / scale it to fit in the available space? I don't know, but it doesn't.
Oh and on another note, the 'Stop Generating Unnecessary Thumbnails' Plugin only 'prevents' unwanted sizes for the automatic WordPress generation of alternate image sizes when a new image is uploaded (and also for itself). It doesn't prevent other Thumbnail regeneration products from generating whatever they want to or are configured to purposely generate.
Cleanup of 'Thumbnails' (AKA Alternative Image Sizes)
Thumbnail Cleaner, Regenerate Thumbnails (from ShortPixels) and Media Cleaner (Pro version for the latter)
Thumbnail Cleaner: Good for focusing on getting rid of old thumbnails (Alternate Image Sizes). OK, here's the situation: You're switching to Real Thumbnail Generator and want to get rid of all the Alternate Image Sizes (AIS) in the Uploads Directory / 'flat file structure'. Clean up thumbnails before installing the Real Thumbnail Generator is the best option. That's because it will scan and delete files in sub directories and those will need to be re-created too. No big deal unless there are a lot of images.
Media Cleaner (Pro): Good for identifying any unused images (IE, the full size / original images)