7 kyu
link to kata
my solution
Grayscale colors in RGB color model are colors that have the same values for Red, Green and Blue. For example, #606060 is a grayscale color, while #FF0055 is not.
In order to correctly convert a color to grayscale, one has to use luminance Y for Red, Green and Blue components. One can calculate luminance Y through the formula introduced in the NTSC standard:
Y = 0.299 * R + 0.587 * G + 0.114 * B
This formula closely represents the average person's relative perception of the brightness of red, green, and blue light.
Given a color in 6-digit hexidecimal notation #RRGGBB in upper case, convert it to grayscale #YYYYYY. The answer should be a string representing the color code in 6-digit hexidecimal notation in upper or lower case.
Round the value of luminance Y to the closest integer.
All inputs will be valid.