图片相似算法phash

phash.cpp

string pHashValue(Mat &src) {
    // gray
    assert(src.channels() == 1);

    string hash(64, '\0');
    Mat img, dst;
    
    resize(src, img, Size(32, 32));
    img = Mat_<double>(img);

    dct(img, dst);

    dst = dst( Rect(1, 1, 8, 8) );
    Scalar imageMean = mean(dst);

    Mat mask = (dst >= imageMean[0]);
    for (int i = 0; i<mask.rows; i++) {
        for (int j = 0; j<mask.cols; j++) {
            mask.at<uchar>(i, j) == 0 ? (hash[i*mask.cols + j] = '0') 
                : (hash[i*mask.cols + j] = '1');
        }
    }
    return hash;
}

Rect(1, 1, 8, 8) // important