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From: Debabrata Mandal (mandaldebabrata123_at_[hidden])
Date: 2020-08-12 06:16:57

First of all thanks for providing references to some of the new papers that
I had not discovered myself.

Can you give references to any particular papers?
> The names listed below, I think, may be ambiguous to some.

The thing is I did not reference any particular paper when I mentioned
these techniques. One reason was that I could not find the original sources
for the 3 techniques mentioned. But there are dozens of papers discussing
improvements to these 3 barebones algorithms.

For example,
In this book,
Pg - 474 (By, Karel Zuiderveld, 1994) the CLAHE algorithm (a type of block
overlapping HE) is mentioned.

> > 1. Block overlapping HE
> Block Overlapped Intensity-Pair Distribution Approach for Image
> Contrast Enhancement, 2007
> by Md. Hasanul Kabir, M. Abdullah-Al-Wadud, Mohammad A.U. Khan, Abdur
> Rashid and Saghir Ahmad
This paper also talks about an additional 'Intensity-Pair distribution
method' which I am not currently familiar with.

> 2. Partially overlapping HE
> An advanced contrast enhancement using partially overlapped sub-block
> histogram equalization, 2001
> by Joung-Youn Kim ; Lee-Sup Kim ; Seung-Ho Hwang
> This one?

Yes I too was referencing from this paper.

> 3. Non-overlapping HE
> Block based Intensity-Pair Distribution for Image Contrast Enhancement,
> 2006
> by Md. Hasanul Kabir, M. Abdullah-Al-Wadud, Mohammad A.U. Khan, Abdur
> Rashid and Saghir Ahmad
I was unable to find the link to the full paper for this. From the abstract
it seems an re-application of the 'Intensity-Pair distribution method' to
non-overlapping blocks which they had published in a previous paper (the
first paper that you mentioned).

> Another example of possibilities for the 1. and 3., that is
> - non-overlapped sub-blocks HE
> - overlapped sub-blocks HE (as an improvement of the former, to remove
> the blocking effect)
> is explained in this paper, referred w/ citations [13] and [14]:
> Image Contrast Enhancement based Sub-histogram Equalization Technique
> without Over-equalization Noise, 2009
> by Hyunsup Yoon, Youngjoon Han, and Hernsoo Hahn
These are the newer publications on the topic. I have not read them yet.

where the citations [13] and [14] are none of the papers I listed
> earlier, but these:
> [13] F. Lamberti, B. Montrucchio, A. Sanna, "CMBFHE_a novel contrast
> enhancement technique based on cascaded multistep binomial filtering
> histogram equalization", IEEE Transactions on Consumer Electronics,
> 52(3), pp.966-974, 2006.
> [14] Z. Q. Wu, J. A. Ware, I. D. Wilson, J. Zhang, "Mechanism analysis
> of highly overlapped interpolation contrast enhancement", IEEE
> Proceedings Vision, Image & Signal Processing, 153(4), pp.512-520,
> 2006.
> If possible, I think, we should try to settle on common sources of 'truth'
> :-)

Yes I agree, that should be the way. I am keeping that in mind from now

> > The main difference between the three are the technique in which they
> > improve the computation time while keeping undesired effects out.
> > For example, Block overlapping HE performs equalization on a window
> around
> > each and every pixel in the image thus suffering from huge computational
> > costs. Non overlapping HE on the other hand does a bilinear interpolation
> > to find the transformation function for equalization but suffering from
> > something called blocking effect.
> All the three above are techniques for local contrast enhancement.
> Are we also having implementation of classic/canonial global contrast
> enhancement?
Yes, I have already implemented the Global HE which was part of the
proposal. Is that what you had meant by classic/canonial global contrast

> > My goal, as I had mentioned in the proposal was to implement Block
> > overlapping HE (specifically CLAHE - which makes some additions to it).
> But
> > I am not sure which to choose.
> For archives, I'll quote Pranam from #boost-gil channel,
> "if you already have implemented one technique then you should proceed
> with it to speed up things"
> Sure, thanks for the advice. We can make improvements based on the results
we obtain on the initial implementations, since it is difficult both to
decide beforehand which is the best one and at the same time implementing
all possible approaches.

Debabrata Mandal.

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