Is there a way to download the high-resolution photo after editing it on Google Photos built-in editing tool? I often upload pictures and fool around with the editing, but then I'm only able to download a much smaller version. For instance, a 5.8MB file downloads to only 1.36MB, clearly a large reduction in file size.
When I use Google Photos, I always seem to have option of downloading high-res original or edited image. I guess, you used to save image by right-click on image and press "Save Image As" or something similar, like you save images from websites.
But you can download high-res image from menu.
Image "size" may refer to a couple of different things:
Resolution: Most people mean "full resolution" when they say "full size". It is possible to download full-resolution images from Google Photos (as long as they are less than 16mp, you own a Pixel phone, or you pay for storage). (See answer by @aaaaaa.)
If you own a Pixel phone, all images uploaded from the phone will automatically be stored at full resolution. This resolution will apply to any edits performed from within Google Photos.
If you pay for storage, to use resolutions greater than 16mp, you must change the Google Photos upload size to "Original" on each device that you use to access Google Photos.
If any of your edits includes rotation or cropping, the resolution will be reduced to reflect your edits. This is true regardless of whether Google is storing "High Quality" or "Original" images.
Storage Size: This appears to be what you are referring to when you note that a 5.8MB file downloads as 1.36MB. This happens because Google Photos uses JPEG settings that are lower than those used by most digital cameras. Regardless of whether a photo has been edited from within Google Photos, you cannot force Google to use higher JPEG settings.