is it correct to say 'will be agreed
It will be agreed on a specific size for those images so that developed in large size, and the system will coordinate them by three or four sizes used on the site and determine their directions.

Question

Answer

It's actually really confusing.

How about, "A specific size will be agreed upon..."? (We need the subject to be clear.) Still, the rest of the paragraph needs revision.

No pierdas la oportunidad de aprender un idioma desde la comodidad de tu casa. ¡Explora nuestra selección de profesores de idiomas con experiencia e inscríbete ya en tu primera clase!