Unwanted dashed black border when rotating image in php -

i getting unwanted dashed black border when rotate image. have tried remove not finding success. using following function image rotation. try preserve transparency. have provided image well.

here image url: http://s23.postimg.org/hep2pkol7/border.png    function imagerotation ($source, $rotang) {     imagealphablending($source, false);     imagesavealpha($source, true);     $rotation = imagerotate($source, $rotang, imagecolorallocatealpha($source, 0, 0, 0, 127));     imagealphablending($rotation, false);     imagesavealpha($rotation, true);      return $rotation; }  

i call function that:

$rotatedimage = imagerotation($image, 10); 

here full code

<?php     // settings     $text = "previously blogging";      $fontface = 'days.ttf';     $fontsize = 90;     $angle = 0;       $bbox = calculatetextbox($text, $fontface, $fontsize, $angle);     $image = imagecreatetruecolor($bbox['width'], $bbox['height']);     // define colors     $black = imagecolorallocate($image, 0, 0, 0);     $yellow = imagecolorallocate($image, 0xff, 0xff, 0xff);     //fill image background color     imagefill($image, 0, 0, $yellow);     // draw text     imagettftext($image, $fontsize, $angle, $bbox['left'], $bbox['top'], $black, $fontface, $text);       $image = imagerotation($image, 20);       $im = imagecreatefromjpeg('weight-loss.jpg');         // switch antialiasing on 1 image     imageantialias($im, true);     $destwidth = imagesx($im);     $destheight = imagesy($im);     $src_w = imagesx($image);     $src_h = imagesy($image);      $dst_x = ($destwidth - $src_w)/2;     $dst_y = ($destheight - $src_h)/2;      imagecopy($im, $image, $dst_x, $dst_y, 0, 0, $src_w, $src_h);      header ('content-type: image/jpeg');     imagejpeg($im, null, 100);     imagedestroy($im);     imagedestroy($image);           function calculatetextbox($text,$fontfile,$fontsize,$fontangle)     {         $rect = imagettfbbox($fontsize,$fontangle,$fontfile,$text);          $minx = min(array($rect[0],$rect[2],$rect[4],$rect[6]));         $maxx = max(array($rect[0],$rect[2],$rect[4],$rect[6]));         $miny = min(array($rect[1],$rect[3],$rect[5],$rect[7]));         $maxy = max(array($rect[1],$rect[3],$rect[5],$rect[7]));          return array(             "left"   => abs($minx),             "top"    => abs($miny),             "width"  => $maxx - $minx,             "height" => $maxy - $miny,             "box"    => $rect             );     }         function imagerotation ($source, $rotang)     {         imagealphablending($source, false);         imagesavealpha($source, true);         $rotation = imagerotate($source, $rotang, imagecolorallocatealpha($source, 0, 0, 0, 127), 0);         imagealphablending($rotation, false);         imagesavealpha($rotation, true);          return $rotation;     }      ?> 

this neither dashed border, nor border @ actually. happens because images low-resolution, cause the rotated borders "break", because actual pixels don't rotate.

that's i'm trying explain:

1. a line, parallel "pixel construction"; 1 px 3 dashes long:

   ------------------------------------- 

   it smooth.

2. rotated line:

   ---    ---       ---          ---             ---                ---                   ---  

   as see, due low resolution, steps, not smoothly goes down.

if use higher resolution, issue go away. visual effect of "black" border appears because white image contrasts other part of image.