php - centre text between 2 coords -

i trying centre line of text, of known width along line specified start , end coordinates.

the purpose write text around polygon, lines not horizontal.

currently have following function takes start x , y , finish x , y of line , width of text (in pixels).

the text drawn starting @ x1, y1 @ correct angle follow line.

to centre text on line have tried calculate left padding in pixels should applied x1, y1 move text correct amount left origin.

the following function attempt @ modifying coordinates implement above concept. not quite right. end text off line, x out y, depends on face neither x or y correct.

    private function centertextonline(&$x1, &$y1, &$x2, &$y2, $width) {             $distance = $this->getdistance($x1, $y1, $x2, $y2);     //calculate left padding required in pixels     $padding = ($distance - $width) / 2;     //what factor need alter x1, y1 by?     $factor = ($distance / $padding);     $gradient = ($y2-$y1)/($x2-$x1);  //gradient alter y      $x1 += abs($x2-$x1) / $factor; //move start x factor     $y1 += ($gradient / $factor); //add factor of gradient start y     return; } 

if can see error, or knows algorithm purpose, appreciate input.

thanks time.

i think should work:

$y1 += ($y2-$y1)/$factor;  $k = $how_much_distance_i_want/sqrt(1+$gradient*$gradient);  $x1 += $k*$gradient; $y1 -= $k;  return; 

while @ it, think abs in

$x1 += abs($x2-$x1) / $factor; 

can lead unexpected results in case ($x2-$x1) negative (maybe better leave without abs), , depending on how php deals infinities, might want have plan case $factor === 0.