Implementation of different conversion algorithms using OpenCV.
For each pixel, it selects one of the RGB components and assigns it to the other two components of the pixel.
Calculates the average of the three color components and assigns it to all subpixels.
Calculates the average between the maximum and minimum color components and assigns it to all subpixels.
All subpixels get the value obtained by: 0.2126R + 0.7152G + 0.0722B