Automatic Gamma correct

[rolalaro]

• Added several methods for automatic Gamma correction
• Added some methods for mean, stdev and sum in vpImage

[codecov]

Codecov Report

Attention: Patch coverage is 9.09091% with 240 lines in your changes are missing coverage. Please review.

Project coverage is 52.45%. Comparing base (6462b34) to head (d66ad95).

Files	Patch %	Lines
modules/imgproc/src/vpImgproc.cpp	10.64%	193 Missing ⚠️
modules/core/include/visp3/core/vpImage.h	2.08%	47 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1346      +/-   ##
==========================================
- Coverage   52.71%   52.45%   -0.27%     
==========================================
  Files         399      399              
  Lines       51911    52175     +264     
==========================================
+ Hits        27366    27367       +1     
- Misses      24545    24808     +263     

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