function pngMerge($o_pic,$out_pic){
 $begin_r = 255;
 $begin_g = 250;
 $begin_b = 250;
 list($src_w, $src_h) = getimagesize($o_pic);// 获取原图像信息 宽高
 $src_im = imagecreatefrompng($o_pic); //读取png图片
 print_r($src_im);
 imagesavealpha($src_im,true);//这里很重要 意思是不要丢了$src_im图像的透明色
 $src_white = imagecolorallocatealpha($src_im, 255, 255, 255,127); // 创建一副白色透明的画布
 for ($x = 0; $x < $src_w; $x++) {
  for ($y = 0; $y < $src_h; $y++) {
    $rgb = imagecolorat($src_im, $x, $y);
    $r = ($rgb  16) & 0xFF;
    $g = ($rgb  8) & 0xFF;
    $b = $rgb & 0xFF;
    if($r==255 && $g==255 && $b == 255){
    imagefill($src_im,$x, $y, $src_white); //填充某个点的颜色
    imagecolortransparent($src_im, $src_white); //将原图颜色替换为透明色
    }
    if (!($r <= $begin_r && $g <= $begin_g && $b <= $begin_b)) {
     imagefill($src_im, $x, $y, $src_white);//替换成白色
     imagecolortransparent($src_im, $src_white); //将原图颜色替换为透明色
    }
  }
 }
 $target_im = imagecreatetruecolor($src_w, $src_h);//新图
 imagealphablending($target_im,false);//这里很重要,意思是不合并颜色,直接用$target_im图像颜色替换,包括透明色;
 imagesavealpha($target_im,true);//这里很重要,意思是不要丢了$target_im图像的透明色;
 $tag_white = imagecolorallocatealpha($target_im, 255, 255, 255,127);//把生成新图的白色改为透明色 存为tag_white
 imagefill($target_im, 0, 0, $tag_white);//在目标新图填充空白色
 imagecolortransparent($target_im, $tag_white);//替换成透明色
 imagecopymerge($target_im, $src_im, 0, 0, 0, 0, $src_w, $src_h, 100);//合并原图和新生成的透明图
 imagepng($target_im,$out_pic);
 return $out_pic;
}
$o_pic = '1.png';
$name = pngMerge($o_pic,'aaaa.png');
print_r($name);

$o_pic = '1.jpg';
//要处理的色阶起始值
$begin_r = 215;
$begin_g = 215;
$begin_b = 215;
list($src_w,$src_h,$src_type) = getimagesize($o_pic);// 获取原图像信息
$file_ext = get_ext($o_pic);//获取扩展名
$target_im = imagecreatetruecolor($src_w,$src_h);//新图
if($file_ext == 'jpg') //转换JPG 开始
{
  $src_im = ImageCreateFromJPEG($o_pic);
  imagecopymerge($target_im,$src_im,0,0,0,0,$src_w,$src_h,100);
  for($x = 0; $x < $src_w; $x++)
  {
    for($y = 0; $y < $src_h; $y++)
    {
      $rgb = imagecolorat($src_im, $x, $y);
      $r = ($rgb  16) & 0xFF;
      $g = ($rgb  8) & 0xFF;
      $b = $rgb & 0xFF;
      if($r > $begin_r && $g > $begin_g && $b > $begin_b ){  
        imagecolortransparent($target_im, imagecolorallocate($target_im,$r, $g, $b));        
      }
    }
  }
}

$begin_r = 98;
$begin_g = 98;
$begin_b = 98;
list($src_w, $src_h) = getimagesize($o_pic);// 获取原图像信息
$src_im = imagecreatefromjpeg($o_pic);
//imagecopymerge($target_im, $src_im, 0, 0, 0, 0, $src_w, $src_h, 100);
//imagecopyresampled($target_im, $src_im, 0, 0, 0, 0, $src_w, $src_h, $src_w, $src_h);
$i = 0;
$src_white = imagecolorallocate($src_im, 255, 255, 255);
for ($x = 0; $x < $src_w; $x++) {
  for ($y = 0; $y < $src_h; $y++) {
   $rgb = imagecolorat($src_im, $x, $y);
   $r = ($rgb  16) & 0xFF;
   $g = ($rgb  8) & 0xFF;
   $b = $rgb & 0xFF;
   if($r==255 && $g==255 && $b == 255){
     $i ++;
     continue;
   }
   if (!($r <= $begin_r && $g <= $begin_g && $b <= $begin_b)) {
     imagefill($src_im, $x, $y, $src_white);//替换成白色
   }
  }
}
$target_im = imagecreatetruecolor($src_w, $src_h);//新图
$tag_white = imagecolorallocate($target_im, 255, 255, 255);
imagefill($target_im, 0, 0, $tag_white);
imagecolortransparent($target_im, $tag_white);
imagecopymerge($target_im, $src_im, 0, 0, 0, 0, $src_w, $src_h, 100);