php - Calculating a value range in percent -

the following function takes dpi value , returns percentage:

    100%        if value bigger 200     50% 100% if value between 100 , 200     25% 50%  if value between 80 , 100     0%  25%  if value lower 80      static public function interpretdpi($x) {         if ($x >= 200) return 100;         if ($x >= 100 && $x < 200) return 50 + 50 * (($x - 100) / 100);         if ($x >= 80 && $x < 100) return 25 + 25 * (($x - 80) / 20);         if ($x < 80) return 25 * ($x / 80);     } 

now have change function according these rules, returning:

    100%        if value bigger 100     75% 100% if value between 72 , 100     50% 75%  if value between 50 , 72     0%  50%  if value lower 50 

in order achieve this, tried re-model function according how understood behaviour:

    static public function interpretdpi($x) {         if ($x >= 100) return 100;         if ($x >= 72 && $x < 100) return 75 + 75 * (($x - 72) / 28);         if ($x >= 50 && $x < 72) return 50 + 50 * (($x - 50) / 22);         if ($x < 50) return 25 * ($x / 50);     } 

but results plain wrong. dpi of 96 instance give me 141% result. wrong lack mathematical understanding know why - , how fix it.

i must have misunderstood how function works.

can elaborate on this?

that's right idea coefficient numbers in formulas wrong, results 141%.

you should try :

  static public function interpretdpi($x) {    if ($x > 100) return 100;    if ($x > 72 && $x <= 100) return 75 + 25 * (($x - 72) / 28);    if ($x >= 50 && $x <= 72) return 50 + 25 * (($x - 50) / 22);    if ($x < 50) return 50 * ($x / 50);   } 

i think you'll results want, checked it, looks :)