Image Auto-Resizer is a plugin for MyBB 1.8. It auto-resizes uploaded images so that they do not exceed a stipulated maximum width and height (defaulting to 900 pixels for both). It can detect animated GIF and PNG files and (if supported) auto-resize or ignore them. It also supports automatic watermarking of images.

Via the Admin Control Panel (ACP), it is possible to:

• Set the maximum image height and width for image attachments.
  
• Set policies for animated GIFs and for animated PNGs.
  
• Set a watermark image.
  
• Resize all preexisting uploaded image attachments, by clicking "Go" beside Tools & Maintenance -> Recount & Rebuild -> Resize Uploaded Images.
  

Minimum requirements

• MyBB >= 1.8.27.
  

This is because the plugin relies on the mk_path_abs() function introduced in 1.8.27 (in this commit). If you wish to use the plugin on an earlier version of MyBB, then you can copy that function definition into the plugin file.
Installing

1. Download.
   Download an archive of the plugin's files.
   
2. Copy files.
   Extract the files in that archive to a temporary location, and then copy the files in "root" into the root of your MyBB installation.
   
3. Install via the ACP.
   In a web browser, open the "Plugins" module in the ACP of your MyBB installation. You should see "Image Auto-Resizer" under "Inactive Plugins". Click "Install & Activate" next to it. You should then see the plugin listed under "Active Plugins" on the reloaded page.
   
4. Configure settings.
   Navigate in the ACP to Settings -> Plugin Settings -> Image Auto-Resizer and configure your preferred values for the settings.
   
5. Resize preexisting images
   Optionally (but recommended), run "Resize Uploaded Images" as described above.
   

Licence

Image Auto-Resizer is licensed under the GPL version 3.

Maintainers and credits

Image Auto-Resizer was originally authored by Laird to be maintained by the unofficial MyBB Group, as inspired by azalea4va in the MyBB Community Forums thread Resize image attachments, and as suggested by Eldenroot after he read that thread.