GD lib resize image few turns black - php

Question

I am experiencing an issue with image upload by users, out of 100 say 1 or 2 images uploaded are completely black.
here is the function i use for resizing their images, can someone see what could be wrong here?
function resize_image($oldimage_name, $new_image_name){
list($owidth,$oheight) = getimagesize($oldimage_name);
$width = 250; $height = 250;
$im = imagecreatetruecolor($width, $height);
$img_src = imagecreatefromjpeg($oldimage_name);
imagecopyresampled($im, $img_src, 0, 0, 0, 0, $width, $height, $owidth, $oheight);
imagejpeg($im, $new_image_name, 90);
imagedestroy($im);
unlink($oldimage_name);
return true;
}
my error handling code
if($_FILES['file']['name'] == ''){
$error[] = 'Please attach your photo.';
}elseif($_FILES["file"]["size"] > 2097152){
$error[] = 'Selected image size is too large, upload under 2mb.';
}elseif(!in_array($_FILES["file"]["type"], array("image/jpg", "image/jpeg"))){
$error[] = 'We accept only JPG / JPEG image format.';
}
Here is the file upload
if($_FILES['file']['name']!='')
{
$tmp_name = $_FILES["file"]["tmp_name"];
$namefile = $_FILES["file"]["name"];
$cname = str_replace(' ', '-', $candidate_name);
$ext = end(explode(".", $namefile));
$fileUpload = move_uploaded_file($tmp_name,"uploads/images/".$image_name);
$image_name= $cname.'-'.time().".".$ext;
resize_image($tmp_name,"uploads/images/".$image_name);
$img = ''.$image_name.'';
}
what could be causing this? i just cannot seem to understand. out of 100 just 1 or 2 images are completely black i do not know what the users are uploading either because when i try to upload different image types it definitely does not allow me to upload any png or gif files.
Appreciate your time and help