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60 lines
1.7 KiB
C++
60 lines
1.7 KiB
C++
// Copyright 2019 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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// clang-format off
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//[ getting_started_listing_04
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#include <algorithm> // std::max_element
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#include <boost/format.hpp> // only needed for printing
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#include <boost/histogram.hpp> // make_histogram, integer, indexed
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#include <iostream> // std::cout, std::endl
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#include <sstream> // std::ostringstream
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int main() {
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using namespace boost::histogram;
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using namespace boost::histogram::literals;
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/*
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We make a 3d histogram for color values (r, g, b) in an image. We assume the values
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are of type char. The value range then is [0, 256).
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*/
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auto h = make_histogram(
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axis::integer<>(0, 256, "r"),
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axis::integer<>(0, 256, "g"),
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axis::integer<>(0, 256, "b")
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);
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/*
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We don't have real image data, so fill some fake data.
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*/
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h(1, 2, 3);
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h(1, 2, 3);
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h(0, 1, 0);
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/*
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Now let's say we want to know which color is most common. We can use std::max_element on an
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indexed range for that.
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*/
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auto ind = indexed(h);
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auto max_it = std::max_element(ind.begin(), ind.end());
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/*
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max_it is the iterator to the maximum counter. This is the special iterator from indexed_range,
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you can use it to access the cell index as well and the bin values. You need to
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double-dereference it to get to the cell count.
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*/
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std::ostringstream os;
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os << boost::format("count=%i rgb=(%i, %i, %i)")
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% **max_it % max_it->bin(0_c) % max_it->bin(1) % max_it->bin(2);
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std::cout << os.str() << std::endl;
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assert(os.str() == "count=2 rgb=(1, 2, 3)");
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}
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//]
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