MyBB Community Forums

Is there a way when people add an image with this function
and it is larger as for example 601 pixels (width) to resize it 600 pixels.

When somebody add an image from 800x600 this must be resized to 600x450
When somebody add an image from 600x800 no resize

to give more details to developers:

1)Does your server's PHP have GD Support.
2)Does this function need to work for just uploaded images or images in signatures too?

GD support yes, but people cannot upload pictures in the message only add a hyperlink (for example photobucket).
Only pictures in the posts must be resized.

Does anyone know a plugin for this? I could have sworn that MyBB did this automatically but when someone posted a bunch of large images on my new 1.4.1 forum, the page was stretched twofold.