hsl_colors #metapost-sandbox

main.mp

vardef hsl_color(expr h, s, l) =
  save chroma, hh, x, m;
  chroma = (1 - abs(2 * l - 1)) * s;
  hh = h / 60;
  x = chroma * (1 - abs(hh mod 2 - 1));
  m = l - chroma / 2;
  if hh < 1: (chroma,x,0)+(m,m,m)
  elseif hh < 2: (x,chroma,0)+(m,m,m)
  elseif hh < 3: (0,chroma,x)+(m,m,m)
  elseif hh < 4: (0,x,chroma)+(m,m,m)
  elseif hh < 5: (x,0,chroma)+(m,m,m)
  else: (chroma,0,x)+(m,m,m)
  fi
enddef;

beginfig(0);

numeric s[], l[];
s0 = 0.5; l0 = 0.3;  % First row: medium saturation, high lightness
s1 = 0.75; l1 = 0.4;  % Second row: high saturation, high lightness
s2 = 1; l2 = 0.5;  % Third row: high saturation, medium lightness

path r;
for y = 0, 1, 2:
  for h = 0 step 15 until 360:
    r := fullcircle scaled 24 shifted (h, -36 * y if y = 2: +8 fi);
    fill r withcolor hsl_color(h, s[y], l[y]);
    draw r withcolor white;
  endfor
endfor

label.urt("Less saturation", (-20, 14));
label.lrt("Lower lightness", (-20, -78));
drawarrow (-15, -21) -- (-15, 12);
drawarrow (-15, -43) -- (-15, -76);

endfig;
end