Function harris_demo

examples/computer_vision/harris.cpp:16–118

using namespace af;

static void harris_demo(bool console) {
    af::Window wnd("Harris Corner Detector");

    // 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;

    // Calculate image gradients
    array ix, iy;
    grad(ix, iy, img);

    // Compute second-order derivatives
    array ixx = ix * ix;
    array ixy = ix * iy;
    array iyy = iy * iy;

    // Compute a Gaussian kernel with standard deviation of 1.0 and length of 5
    // pixels These values can be changed to use a smaller or larger window
    array gauss_filt = gaussianKernel(5, 5, 1.0, 1.0);

    // Filter second-order derivatives with Gaussian kernel computed previously
    ixx = convolve(ixx, gauss_filt);
    ixy = convolve(ixy, gauss_filt);
    iyy = convolve(iyy, gauss_filt);

    // Calculate trace
    array itr = ixx + iyy;
    // Calculate determinant
    array idet = ixx * iyy - ixy * ixy;

    // Calculate Harris response
    array response = idet - 0.04f * (itr * itr);

    // Gets maximum response for each 3x3 neighborhood
    // array max_resp = maxfilt(response, 3, 3);
    array mask     = constant(1, 3, 3);
    array max_resp = dilate(response, mask);

    // Discard responses that are not greater than threshold
    array corners = response > 1e5f;
    corners       = corners * response;

    // Discard responses that are not equal to maximum neighborhood response,
    // scale them to original response value
    corners = (corners == max_resp) * corners;

    // Gets host pointer to response data
    float* h_corners = corners.host<float>();

    unsigned good_corners = 0;