How to perform skin tone matching

Question

( face )

( body )

Hi, i am new to image processing and openCV C/C++. I am wondering that is it possible to extract skin tone from the first image (face

Answer 1

For finding skin you can use one of this formulas:

1) With normilized RGB space:

for(int i = 0; i < m_image->height; ++i)
{
    for(int j = 0; j < m_image->width; ++j)
    {
        if (m_image->nChannels == 3)
        {
            int valueR = (reinterpret_cast(m_image->imageData + i * m_image->widthStep))[j * 3 + 2];
            int valueG = (reinterpret_cast(m_image->imageData + i * m_image->widthStep))[j * 3 + 1];
            int valueB = (reinterpret_cast(m_image->imageData + i * m_image->widthStep))[j * 3];

            float normR = static_cast(valueR) / static_cast(valueR + valueG + valueB);
            float normG = static_cast(valueG) / static_cast(valueR + valueG + valueB);
            float normB = static_cast(valueB) / static_cast(valueR + valueG + valueB);

            if ((normB / normG < 1.249) &&
                (( normR + normG + normB ) / ( 3 * normR ) > 0.696 ) &&
                ( 1/3.0 - normB/( normR + normG + normB ) > 0.014 ) &&
                (normG/(3* (normR + normG + normB)) < 0.108 ))
            {
              //pixel is skin
            }
        }
 }

2) in RGB space:

for(size_t i = 0; i < m_image->height; ++i)
{
    for(size_t j = 0; j < m_image->width; ++j)
    {
        if (m_image->nChannels == 3)
        {
            int R = (reinterpret_cast(m_image->imageData + i * m_image->widthStep))[j * 3 + 2];
            int G = (reinterpret_cast(m_image->imageData + i * m_image->widthStep))[j * 3 + 1];
            int B = (reinterpret_cast(m_image->imageData + i * m_image->widthStep))[j * 3];

            if (( R > 95) && ( G > 40 ) && ( B > 20 ) &&
                (std::max(R, std::max( G, B) ) - std::min(R, std::min(G, B) ) > 15) &&
                (std::abs(R - G) > 15) && (R > G) && (R > B))
            {
                //skin pixel
            }

        }
    }

3) in YCrCb space:

for(size_t i = 0; i < m_image->height; ++i)
{
    for(size_t j = 0; j < m_image->width; ++j)
    {
        if (m_image->nChannels == 3)
        {
            int Cr = (reinterpret_cast(image->imageData + i * image->widthStep))[j * 3 + 2];
            int Cb = (reinterpret_cast(image->imageData + i * image->widthStep))[j * 3 + 1];
            int Y = (reinterpret_cast(image->imageData + i * image->widthStep))[j * 3];

            if (( Y > 80 ) && ( Cb > 85 ) && ( Cb < 135 ) &&
                (Cr > 135) && (Cr < 180))
            {
              //skin pixel
            }           
        }
    }
}