get_pgm_diff.cpp

/*
 * Simpledjvu-0.1
 * Based on djvulibre (http://djvu.sourceforge.net/)
 * Copyright 2012, Mikhail Dektyarev <mihail.dektyarow@gmail.com>
 *
 * This file is part of Simpledjvu.
 * 
 * Simpledjvu is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * Simpledjvu is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with Simpledjvu.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include <djvulibre.h>

#include <iostream>
#include <cmath>
#include <vector>

using std::vector;

vector<vector<int> > get_image_diff(const GBitmap &image1, const GBitmap &image2) {
    vector<vector<int> > result(image1.columns(), vector<int> (image1.rows()));

    for (int i = 0; i < result.size(); ++i) {
        for (int j = 0; j < result[i].size(); ++j) {
            result[i][j] = static_cast<int>(image1[i][j])  - static_cast<int>(image2[i][j]);
        }
    }

    return result;
}

double Lp_norm(const vector<vector<int> > &data, double p = 1.0) {
    double result(0.0);

    for (int i = 0; i < data.size(); ++i) {
        for (int j = 0; j < data[i].size(); ++j) {
            result += pow(fabs(data[i][j]), p);
        }
    }

    return pow(result, 1.0 / p);
}

double Lp_diff(const GBitmap &image1, const GBitmap &image2, double p = 2.0) {
    vector<vector<int> > diff = get_image_diff(image1, image2);

    return Lp_norm(diff, p);
}

int main(int argc, char *argv[]) {
    GP<GBitmap> gimage1 = GBitmap::create(*ByteStream::create(GURL::Filename::UTF8(argv[1]), "rb"));
    GP<GBitmap> gimage2 = GBitmap::create(*ByteStream::create(GURL::Filename::UTF8(argv[2]), "rb"));

    if (gimage1->columns() != gimage2->columns() || gimage1->rows() != gimage2->rows()) {
        std::cerr << "Image sizes don't match\n";
        return 1;
    }

    auto diff = get_image_diff(*gimage1, *gimage2);

    std::cout << Lp_norm(diff, 1.0) << "  " << Lp_norm(diff, 2.0) << '\n';
    return 0;
}