Histogram - bins values?

I have come across a definition of a term, uniformity which is
"the sum of the square of the histogram bins value".

I don't understand what this means. Please can someone explain what it means? thanks

Judging from the first few paragraphs of this wikipedia article I would interpret a 'bin value' as the number of things in the 'bin', which are the intervals, and you square that and sum it up. If this is misleading I shall delete my post.

well that's what I thought it meant but it didn't make much sense to me...but if you agree then I suppose thats good enugh

Does it make sense for the defintion/context?

well the context is uniformity in images. If you consider the image in terms of its pixel values then you get a histogram. An image with 100 pixels of the same value should have a uniformity of 1. So I don't know how the definition fits...unless it is considering the probability value squred?

could it be talking about doing a chi squared test (of uniformity)?

probably more context would help.

Here is a link to the original source

https://books.google.co.uk/books?id=rr7LBQAAQBAJ&pg=PA324&lpg=PA324&dq=uniformity+square+histogram+bins&source=bl&ots=wrtDTzDBUc&sig=DVZFMtf8s_Yi_NJzTDeI6yRwsO8&hl=en&sa=X&ved=0CC0Q6AEwAmoVChMI7IG2kNLtyAIVwVkaCh005AGt#v=onepage&q=uniformity%20square%20histogram%20bins&f=false