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From: Mateusz Loskot (mateusz_at_[hidden])
Date: 2020-08-11 18:38:24

On Mon, 10 Aug 2020 at 08:45, Debabrata Mandal
<mandaldebabrata123_at_[hidden]> wrote:
> I have been doing some reading up for the past few days on the adaptive
> histogram equalization which is expected to have superior performance to HE.
> There are a few options:

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

> 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 one?
AFAIK, there are variants, block overlapped, multiple/layered block
overlapped, perhaps more.

> 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?

> 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

Contrast enhancement using non-overlapped sub-blocks and local
histogram projection, 2011
by Bin Liu ; Weiqi Jin ; Yan Chen ; Chongliang Liu ; Li Li

or something else?


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

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,

If possible, I think, we should try to settle on common sources of 'truth' :-)

> 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

> 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"

> FYI, I have already implemented CLAHE once in MATLAB so doing it in C++
> would not be difficult for me.

Sounds good indeed.

Best regards,

Mateusz Loskot,

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