Hi everyone!
My apologies for not seeing this thread sooner, I was out on leave.
Sorry that there is some confusion about what this plugin does. I’m going to try to clarify it here, and I will update the description to avoid others being confused going forward.
Prior to WordPress 5.3, there were many instances where an upload would fail silently. This most commonly happened when an image the post-processing of the registered image sizes failed to be generated. This was common on sites with low server resources, many (10s or 100s) of registered image sizes, or very large registered image sizes.
Starting in 5.3, a new message will be displayed for all miscellaneous failures that occur during upload suggesting the user try uploading a smaller image. This is the error message quoted above.
“Post-processing of the image failed. If this is a photo or a large image, please scale it down to 2500 pixels and upload it again.”
If you are experiencing this issue, and have tried this plugin, then there is likely something else happening with your site that is causing the issue. This should be investigated separately in the general support forums. It’s possible that the new image processing features need to be adjusted to work on more servers. Investigating these issues will help find where adjustments are needed.
For further context, the concept of BIG images is only used when it comes to the full size image. Starting with version 5.3, if an image is uploaded that is larger than 2500px (by default), a 2500px wide image will be created. That image will be used as the source anywhere that “Full” is selected as the image size, and for generating any smaller image sizes on upload (larger ones will use the true original size).
The only purpose of this plugin is to disable that feature. Some sites need to be able to display the true, un-scaled, original image as the “Full” image size (Photography sites, sites with large format infographics, etc.).
I am going to mark this resolved because the issues being described are unrelated to the code in the plugin.
Also, in the future, please open a separate support forum topic for each time you experience an issue. This adds wider visibility to problems, and helps you receive better support.