I'm trying to take existing images and shrink the file size down by resizing to photos to a smaller resolution. I've tried a few methods so far:

1. Simply editing the photo in photoshop and reuploaded, replacing the existing (and larger) file.
2. I tried the Imsanity plugin and set the options to be less than 1024x1024 and then bulk resized the images without failure (but it did not do the trick).
3. I also tried the Regenerate Thumbnails plugin, and ran the rebuild without failure (but it did not resize the photos).

Maybe there is a better or a right way to accomplish what I'm doing, but I can't seem to find anything on this issue.

I'm running a Multisite install and WP FTP is not enabled and can't be enabled to solve this.