Update brightness tutorial

[s-trinh]

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Update brightness tutorial:

• use vpDisplayFactory and scale the image by 2 for small display resolution
• display both color and gray results
• cycle across the different automatic gamma method to display the results

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 53.90%. Comparing base (520efed) to head (db58506). Report is 23 commits behind head on master.

Files with missing lines	Patch %	Lines
modules/imgproc/src/vpImgproc.cpp	0.00%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1482      +/-   ##
==========================================
+ Coverage   53.88%   53.90%   +0.02%     
==========================================
  Files         442      442              
  Lines       53778    53791      +13     
==========================================
+ Hits        28978    28996      +18     
+ Misses      24800    24795       -5     

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[s-trinh]

Not a tutorial code but I have added tutorial-compare-auto-gamma.cpp sample code that can be used to easily compare the results between the different auto Gamma methods.

Can be used with one image:

• ./tutorial-compare-auto-gamma --input Sample_low_brightness.png

or with a sequence of images:

• ./tutorial-compare-auto-gamma --input visp-images/mbt/cube/image%04d.png --output Results/cube

---

I don't know if the inverse Gamma is needed here: https://github.com/lagadic/visp/blob/a65eebc2fffc3814889fbe40c3b1a8ee182d1bd4/modules/imgproc/src/vpImgproc.cpp#L332

Without

log_gamma_computed=0.254357

log_gamma_computed=2.69225

log_gamma_computed=1.24885

• image from wikimedia

• images from Testing Images/DICM

With