Hello,

Unfortunately, this isn't possible without writing some custom code. I would recommend you to check our code of our image editor, to see, how to programmatically resize an image. It is located in the method "private void SaveImage(string name, string extension, string mimetype, byte[] binary, int width, int height)" in the file "CMSAdminControls\ImageEditor\ImageEditor.ascx.cs". You would have also to alter the MediaGalery web part.

I hope this helps.

Best regards,
Boris Pocatko