Abstract
We present an image processing technique, the improved OMC filter (also called Madmax), which selects maxima of convexities of intensity modulations of an image. The filter computes second derivatives of the image in multiple directions around each pixel. It is shown to be efficient for pattern recognition, and bright hair-like or small anisotropic features can be enhanced. The filter is tested on artificially generated images, and the effect of a different number of directions in which the second derivatives are calculated is evaluated. Ca ii H line images of spicules and prominences obtained with Hinode/SOT are also used to illustrate its efficiency on real data. It is shown how to make the choice of the sensitive parameters to be used in improving the image visibility.
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Acknowledgements
Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA, ESA and STFC (UK) as international partners. This work has been supported by the Center for International Scientific Studies & Collaboration (CISSC) and the French Embassy in Tehran and by the Iran National Foundation (INSF) that E.T. gratefully acknowledges. This work has been supported financially by Center for Excellence in Astronomy & Astrophysics (CEAA – RIAAM) under research project No. 1/2648. The image processing OMC software (often called Madmax for 8 directions) written for IDL is easily downloadable from the O. Koutchmy site at UPMC, see http://www.ann.jussieu.fr/~koutchmy/debruitage/madmax.pro .
Discussions and remarks from our anonymous referee were very helpful in improving the first version of this manuscript.
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Image Processing in the Petabyte Era
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Tavabi, E., Koutchmy, S. & Ajabshirizadeh, A. Increasing the Fine Structure Visibility of the Hinode SOT Ca ii H Filtergrams. Sol Phys 283, 187–194 (2013). https://doi.org/10.1007/s11207-012-0011-z
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DOI: https://doi.org/10.1007/s11207-012-0011-z