在图片上添加透明度渐变的效果

今天因为临时需要，要动态的在图片上添加透明度渐变的效果，在网上找了半天没有相应功能的算法.... ////$imgsrc = imagecreatefromstring($strimgsrc);$imgsrc = imagecreatefromjpeg("5307754.jpg");$imgsrcw = imagesx($imgsrc);$imgsrch = imagesy($imgsrc);$width = 30;$x1 = 2;$x2 = $imgsrcw - $x1 - 20;$y1 = ($imgsrch - $width) - 2;$y2 = $y1 + $width;$steps = $x2 - $x1; for($i = 0; $i { $alphax = round($i/($steps/127))+60; if($alphax >= 128) $alphax = 127; $alpha = imagecolorallocatealpha($imgsrc, 255, 255, 255, $alphax); imagefilledrectangle($imgsrc, ($i+$x1), $y1, ($i+$x1+1), $y2, $alpha);}header('content-type: image/jpeg');imagejpeg($imgsrc);imagedestroy($imgsrc);?>