image_processing/pyramids.cpp

/*******************************************************
 * Copyright (c) 2014, ArrayFire
 * All rights reserved.
 *
 * This file is distributed under 3-clause BSD license.
 * The complete license agreement can be obtained at:
 * http://arrayfire.com/licenses/BSD-3-Clause
 ********************************************************/
 
#include <arrayfire.h>
#include <stdio.h>
#include <cstdlib>
 
using namespace af;
 
static const float pyramid_kernel[] = {1,  4, 6,  4,  1,  4, 16, 24, 16,
                                       4,  6, 24, 36, 24, 6, 4,  16, 24,
                                       16, 4, 1,  4,  6,  4, 1};
 
array pyramid(const array& img, const int level, const bool sampling) {
    array pyr = img.copy();
    array kernel(5, 5, pyramid_kernel);
    kernel = kernel / 256.f;
    if (sampling) {  // Downsample
        for (int i = 0; i < level; i++) {
            for (int j = 0; j < pyr.dims(2); j++)
                pyr(span, span, j) = convolve(pyr(span, span, j), kernel);
            pyr = pyr(seq(0, pyr.dims(0) - 1, 2), seq(0, pyr.dims(1) - 1, 2),
                      span);
        }
    } else {  // Up sample
        for (int i = 0; i < level; i++) {
            array tmp =
                constant(0, pyr.dims(0) * 2, pyr.dims(1) * 2, pyr.dims(2));
            tmp(seq(0, 2 * pyr.dims(0) - 1, 2), seq(0, 2 * pyr.dims(1) - 1, 2),
                span) = pyr;
            for (int j = 0; j < pyr.dims(2); j++)
                tmp(span, span, j) = convolve(tmp(span, span, j), kernel * 4.f);
            pyr = tmp;
        }
    }
    return pyr;
}
 
void pyramids_demo() {
    af::Window wnd_rgb("Image Pyramids - RGB Images");
    af::Window wnd_gray("Image Pyramids - Grayscale Images");
    wnd_rgb.setPos(25, 25);
    wnd_gray.setPos(150, 150);
 
    array img_rgb =
        loadImage(ASSETS_DIR "/examples/images/atlantis.png", true) /
        255.f;  // 3 channel RGB       [0-1]
    array img_gray = colorSpace(img_rgb, AF_GRAY, AF_RGB);
 
    array downc1 = pyramid(img_rgb, 1, true);
    array downc2 = pyramid(img_rgb, 2, true);
    array upc1   = pyramid(img_rgb, 1, false);
    array upc2   = pyramid(img_rgb, 2, false);
 
    array downg1 = pyramid(img_gray, 1, true);
    array downg2 = pyramid(img_gray, 2, true);
    array upg1   = pyramid(img_gray, 1, false);
    array upg2   = pyramid(img_gray, 2, false);
 
    while (!wnd_rgb.close() && !wnd_gray.close()) {
        wnd_rgb.grid(2, 3);
        wnd_rgb(0, 0).image(img_rgb, "color image");
        wnd_rgb(1, 0).image(downc1, "downsample 1 level");
        wnd_rgb(0, 1).image(downc2, "downsample 2 levels");
        wnd_rgb(1, 1).image(upc1, "upsample 1 level");
        wnd_rgb(0, 2).image(upc2, "upsample 2 level");
        wnd_rgb.show();
 
        wnd_gray.grid(2, 3);
        wnd_gray(0, 0).image(img_gray, "grayscale image");
        wnd_gray(1, 0).image(downg1, "downsample 1 level");
        wnd_gray(0, 1).image(downg2, "downsample 2 levels");
        wnd_gray(1, 1).image(upg1, "upsample 1 level");
        wnd_gray(0, 2).image(upg2, "upsample 2 level");
        wnd_gray.show();
    }
}
 
int main(int argc, char** argv) {
    int device = argc > 1 ? atoi(argv[1]) : 0;
 
    try {
        af::setDevice(device);
        af::info();
        printf("** ArrayFire Image Pyramids Demo **\n\n");
        pyramids_demo();
 
    } catch (af::exception& e) {
        fprintf(stderr, "%s\n", e.what());
        throw;
    }
 
    return 0;
}