computer_vision/fast.cpp

/*******************************************************
 * Copyright (c) 2015, ArrayFire
 * All rights reserved.
 *
 * This file is distributed under 3-clause BSD license.
 * The complete license agreement can be obtained at:
 * https://arrayfire.com/licenses/BSD-3-Clause
 ********************************************************/

#include <arrayfire.h>
#include <cstdio>
#include <cstdlib>

using namespace af;

static void fast_demo(bool console) {
    // Load image
    array img_color;
    if (console)
        img_color = loadImage(ASSETS_DIR "/examples/images/square.png", true);
    else
        img_color = loadImage(ASSETS_DIR "/examples/images/man.jpg", true);
    // Convert the image from RGB to gray-scale
    array img = colorSpace(img_color, AF_GRAY, AF_RGB);
    // For visualization in ArrayFire, color images must be in the [0.0f-1.0f]
    // interval
    img_color /= 255.f;

    features feat = fast(img, 20.0f, 9, true, 0.05);

    float* h_x = feat.getX().host<float>();
    float* h_y = feat.getY().host<float>();

    // Draw draw_len x draw_len crosshairs where the corners are
    const int draw_len = 3;
    for (size_t f = 0; f < feat.getNumFeatures(); f++) {
        int x                                            = h_x[f];
        int y                                            = h_y[f];
        img_color(y, seq(x - draw_len, x + draw_len), 0) = 0.f;
        img_color(y, seq(x - draw_len, x + draw_len), 1) = 1.f;
        img_color(y, seq(x - draw_len, x + draw_len), 2) = 0.f;

        // Draw vertical line of (draw_len * 2 + 1) pixels centered on  the
        // corner Set only the first channel to 1 (green lines)
        img_color(seq(y - draw_len, y + draw_len), x, 0) = 0.f;
        img_color(seq(y - draw_len, y + draw_len), x, 1) = 1.f;
        img_color(seq(y - draw_len, y + draw_len), x, 2) = 0.f;
    }

    freeHost(h_x);
    freeHost(h_y);

    printf("Features found: %zu\n", feat.getNumFeatures());

    if (!console) {
        af::Window wnd("FAST Feature Detector");

        // Previews color image with green crosshairs
        while (!wnd.close()) wnd.image(img_color);
    } else {
        af_print(feat.getX());
        af_print(feat.getY());
    }
}

int main(int argc, char** argv) {
    int device   = argc > 1 ? atoi(argv[1]) : 0;
    bool console = argc > 2 ? argv[2][0] == '-' : false;

    try {
        af::setDevice(device);
        af::info();
        printf("** ArrayFire FAST Feature Detector Demo **\n\n");
        fast_demo(console);

    } catch (af::exception& ae) {
        fprintf(stderr, "%s\n", ae.what());
        throw;
    }

    return 0;
}