Decades, skin color-based face detection algorithms have been developed by means of various color models. As for skin color characteristics, however, false positive rates would increase and detection rates
decrease when an image contains a complicated background or many
spots whose colors are similar to the skin color. In contrast, as the
appearance-based face detection method based mainly on the sliding window means scans the whole image and utilizes learning data,
it maintains high face detection rates but the computational costs are
also high. Thus, as the size of an image increases, the scanning process involves a lot of computational costs and processing time.