Boost C++ Libraries

libs/gil/example/morphology.cpp

//
// Copyright 2021 Prathamesh Tagore <prathameshtagore@gmail.com>
//
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//

#include <boost/gil.hpp>
#include <boost/gil/extension/io/png.hpp>
#include <iostream>
#include <map>
#include <string>
#include <vector>


// Demonstrates a number of morphological operations
// The structuring element is defined as an instance of a kernel_2d<float>:
// Default structuring element is SE = [1,1,1]
//                                     |1,1,1|
//                                     [1,1,1]
// SE(1,1)(center pixel) is the one which coincides with the currently
// considered pixel of the image to be convolved. The structuring element can be
// easily changed by the user.
// The example demonstrates the following morphological operations:
//     - black_hat
//     - top_hat
//     - morphological_gradient
//     - dilation
//     - erosion
//     - opening
//     - closing
//     - binary
// These operations are defined in include/boost/gil/image_processing/morphology.hpp

namespace gil = boost::gil;
int main(int argc, char** argv)
{
    std::map<std::string, bool> operations;
    if (argc < 4 || argc > 11)
    {
        throw std::invalid_argument(
            "Wrong format of command line arguments.\n"
            "Correct format is <Input_image.png> <Output_image_template>"
            " <operation1> <operation2> <operation3> <operation4> <operation5> "
            "<operation6>"
            " <operation7> <operation8>\n");
        // User has to enter atleast one operation and they can enter maximum 8
        // operations considering binary conversion to be an
        // operation.Output_image_template argument is the common component which
        // will be added in names of all output images followed by a hyphen and
        // the operation name.
        // Example :
        // ./example_morphology morphology_original.png out black_hat top_hat
        // morphological_gradient dilation erosion opening closing binary
        // Order of arguments entered will not matter with the exception of binary
        // operation used for binary morphological operations.If binary is entered
        // through the command line, it will always be the first operation to be
        // applied.
        return -1;
    }
    else
    {
        for (int i = 3; i < argc; ++i)
            operations[argv[i]] = true;
    }
    gil::gray8_image_t img;
    gil::read_image(argv[1], img, gil::png_tag{});

    // Image can be converted to a binary format with high value as 255 and low
    // value as 0 by using the threshold operator . This can be used for binary
    // morphological operations . Convenient threshold for binary conversion may
    // be chosen by the user.
    if (operations["binary"])
    {
        threshold_binary(view(img), view(img), 170, 255);
        std::string name = argv[2];
        name += "-binary.png";
        gil::write_view(name, view(img), gil::png_tag{});
    }

    std::vector<float> ker_vec(9, 1.0f); // Structuring element
    gil::detail::kernel_2d<float> ker_mat(ker_vec.begin(), ker_vec.size(), 1, 1);
    gil::gray8_image_t img_out_dilation(img.dimensions()), img_out_erosion(img.dimensions()),
        img_out_opening(img.dimensions());
    gil::gray8_image_t img_out_closing(img.dimensions()), img_out_mg(img.dimensions()),
        img_out_top_hat(img.dimensions());
    gil::gray8_image_t img_out_black_hat(img.dimensions());

    // Do not pass empty input image views in functions defined below for
    // morphological operations to avoid errors.
    if (operations["dilation"])
    {
        // dilate(input_image_view,output_image_view,structuring_element,iterations)
        dilate(view(img), view(img_out_dilation), ker_mat, 1);
        std::string name = argv[2];
        name += "-dilation.png";
        gil::write_view(name, view(img_out_dilation), gil::png_tag{});
    }

    if (operations["erosion"])
    {
        // erode(input_image_view,output_image_view,structuring_element,iterations)
        erode(view(img), view(img_out_erosion), ker_mat, 1);
        std::string name = argv[2];
        name += "-erosion.png";
        gil::write_view(name, view(img_out_erosion), gil::png_tag{});
    }

    if (operations["opening"])
    {
        // opening(input_image_view,output_image_view,structuring_element)
        opening(view(img), view(img_out_opening), ker_mat);
        std::string name = argv[2];
        name += "-opening.png";
        gil::write_view(name, view(img_out_opening), gil::png_tag{});
    }

    if (operations["closing"])
    {
        // closing(input_image_view,output_image_view,structuring_element)
        closing(view(img), view(img_out_closing), ker_mat);
        std::string name = argv[2];
        name += "-closing.png";
        gil::write_view(name, view(img_out_closing), gil::png_tag{});
    }

    if (operations["morphological_gradient"])
    {
        // morphological_gradient(input_image_view,output_image_view,structuring_element)
        morphological_gradient(view(img), view(img_out_mg), ker_mat);
        std::string name = argv[2];
        name += "-morphological_gradient.png";
        gil::write_view(name, view(img_out_mg), gil::png_tag{});
    }

    if (operations["top_hat"])
    {
        // top_hat(input_image_view,output_image_view,structuring_element)
        top_hat(view(img), view(img_out_top_hat), ker_mat);
        std::string name = argv[2];
        name += "-top_hat.png";
        gil::write_view(name, view(img_out_top_hat), gil::png_tag{});
    }

    if (operations["black_hat"])
    {
        // black_hat(input_image_view,output_image_view,structuring_element)
        black_hat(view(img), view(img_out_black_hat), ker_mat);
        std::string name = argv[2];
        name += "-black_hat.png";
        gil::write_view(name, view(img_out_black_hat), gil::png_tag{});
    }
}