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dc9ba74cb3
* Add docs for histogram * Add docs and make changes: - Made changes suggested in first review - Add docs for relevant files * Rename docs file and correct typos * Change doc for cumulative histogram * Add docs for histogram equalization * Make changes suggested in review * Add docs * Remove docs for algorithms * Move images to test_images Co-authored-by: Mateusz Łoskot <mateusz@loskot.net>
67 lines
1.7 KiB
ReStructuredText
67 lines
1.7 KiB
ReStructuredText
.. _sub_histogram:
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Making a sub-histogram
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======================
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Overview
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--------
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Sub-histogram is a subset of a histogram or one that is formed by masking out a
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few axis of the parent histogram.
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GIL class histogram provides these functions as members and returns an instance of
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the desired sub-class.
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#. Histogram over fewer axes
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**Task** - Get a 2D histogram from a 3D RGB histogram over red and green axes
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.. code-block:: cpp
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histogram<int, int, int> h;
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gil::rgb8_image_t img;
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/*
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Fill img ...
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*/
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fill_histogram(view(img), h, false);
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auto sub_h = h.sub_histogram<0, 1>(); // sub_h is a 2D histogram
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Demo output:
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.. code-block:: cpp
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h is {{1, 2, 3} : 1,
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{1, 4, 3} : 2,
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{1, 2, 5} : 3}
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sub_h would be {{1, 2} : 4, {1, 4} : 2}
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#. Histogram using a particular key range
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**Task** - Get a 2D histogram from a 3D RGB histogram for bins whose red color lie between 10 - 20
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and blue color lie between 2 - 10
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.. code-block:: cpp
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histogram<int, int, int> h;
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gil::rgb8_image_t img;
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/*
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Fill img ...
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*/
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fill_histogram(view(img), h, false);
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std::tuple<int, int, int> low, high;
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low = {10, 0, 2} // Since no check over blue channel pass any dummy value
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high = {20, 0, 10} // Since no check over blue channel pass any dummy value
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auto sub_h = h.sub_histogram<0, 2>(low, high); // In angle brackets pass the relevant dimensions in order
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Demo Output:
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.. code-block:: cpp
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h is {{11, 2, 3 } : 1,
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{1 , 4, 11} : 2,
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{1 , 2, 1 } : 3,
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{11, 3, 3 } : 4}
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sub_h would be {{11, 2, 3} : 1, {11, 3, 3} : 4}
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