[IPOL announce] new article: Midway Video Equalization
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Mon Apr 24 00:57:55 CEST 2017
A new article is available in IPOL: http://www.ipol.im/pub/art/2017/181/
Javier Sánchez,
Midway Video Equalization,
Image Processing On Line, 7 (2017), pp. 65–80.
https://doi.org/10.5201/ipol.2017.181
Abstract
This article presents an implementation of the 'Midway Equalization'
method for videos. This technique allows us to modify the image
histograms so that they present similar luminances. We propose two
algorithms: the first one based on histogram inversion and the second
one on the sorting of images intensities. The former computes the
histograms and then finds the contrast change functions by convolving
the inverse histograms with a Gaussian function. The latter starts by
sorting the pixels of each image by intensity; the temporal signals,
composed of all gray levels of the same rank, are then convolved with a
Gaussian function. In this sorting method, the resulting histograms are
more similar and homogeneous. Nevertheless, the histogram strategy is
faster and provides good results in general. The algorithms include a
'dithering' option for reducing quantization artifacts. The whole
implementation depends on a single parameter, the standard deviation,
that is used for Gaussian convolutions. The experiments show several
examples, including the quantization artifacts that appear in some
situations and the benefits of dithering. We observe that these
artifacts are usually more important in the histogram method.
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