Handle max_kb in nokia.image-processing localmsg api

I tested with several images, the size of generated image is about 10%-20% larger than the given size which I think it's acceptable.
Did you mean the three cases:
  - only `max_kb` is specified
  - `max_hres` and `max_vres` are specified, but no `max_kb`
  - `max_kb`, `max_hres` and `max_vres` are all specified
?
Is there any order for those three limits?