How to convert Colors to Grayscale in java with just the java.io.*; library?

Question

Well, i got this.. cause in my place they request it like that.. Well i have this: //some variables and coments are a possible code.. But i mean i don\'t know how to do it exact

Answer 1

// constant factors
            final double GS_RED   = 0.299;
            final double GS_GREEN = 0.587;
            final double GS_BLUE  = 0.114;

Now retrieve each and gett it's red, blue, green component and alpha if exist and multiply them with their corresponding factor.

R = G = B = (int)(GS_RED * R + GS_GREEN * G + GS_BLUE * B);