Manipulating an image in PHP results in striped pattern - php

Question

Edit: Just ended up using Image Magick and that fixed it.
Long story short, I'm attempting to pull some basic information about a series of schools from Wikipedia using a combination of PHP and jQuery. Part of that information is the school's emblem or logo, which is easy enough to find in the elements list.
The problem lies in trying to do some tweaking on the image in PHP. I know the image exists at the target URL (which is on a different domain, if that helps any) and that it's the one I want, but certain images come out looking like this:
This is the original image:
Others, of all file types, come out perfectly fine.
The code for that part is as follows:
$ext = end(explode('.', $image));
if($ext == 'png') {
$img = imagecreatefrompng($image);
}
else if($ext == 'jpeg' || $ext == 'jpg') {
$img = imagecreatefromjpeg($image);
}
else if($ext == 'gif') {
$img = imagecreatefromgif($image);
}
else $img = false;
if($img) {
$raw_x = imagesx($img);
$raw_y = imagesy($img);
if($raw_x > $raw_y && $raw_x > 500)
{
$y = (500 / $raw_x) * $raw_y;
$tmp_img = imagecreatetruecolor(500, $y);
$white = imagecolorallocate($tmp_img, 255, 255, 255);
imagefill($tmp_img, 0, 0, $white);
imagecopyresampled($tmp_img, $img, 0, 0, 0, 0, 500, $y, $raw_x, $raw_y);
$img = $tmp_img;
}
else if($raw_y > 500)
{
$x = (500 / $raw_y) * $raw_x;
$tmp_img = imagecreatetruecolor($x, 500);
$white = imagecolorallocate($tmp_img, 255, 255, 255);
imagefill($tmp_img, 0, 0, $white);
imagecopyresampled($tmp_img, $img, 0, 0, 0, 0, $x, 500, $raw_x, $raw_y);
$img = $tmp_img;
}
if(!file_exists("../images/schools/" . $id)) mkdir("../images/schools/" . $id, 0755, true);
imagejpeg($img, "../images/schools/" . $id . "/photo.jpg", 100);
}
I've been at this for a couple days and I can't figure out what's wrong, I'm hoping a fresh set of eyes might be able to see something I don't

Answer 1

My guess is that your conditional logic around raw image size is causing you problems. You are not handling the case where you image equal in width and height and you are not handling cases where the images are less than 500 pixels (not sure if this is intentional, but could lead to problems with HTML layout if you specify specific heights/widths for your img elements). You should do all your math to calculate expected scaled image size up front and then do image creation/resizing in one place (not in if conditionals).
I am assuming you want to always scale your image to be either 500px in height (if image is portrait) or 500px in width if image is landscape. You would calculate expected dimensions as follows:
$target_width = 500;
$target_height = 500;
if($raw_x >= $raw_y) { // set scaling factor based on x dimension
$scaling_factor = 500.0 / $raw_x;
$target_height = intval(500 * $scaling_factor);
} else { // set scaling factor based on y dimension
$scaling_factor = 500.0 / $raw_y;
$target_width = intval(500 * $scaling_factor)
}
And then only have one code block for setting new temp image and resizing original into it:
$tmp_img = imagecreatetruecolor($target_width, $target_height);
$white = imagecolorallocate($tmp_img, 255, 255, 255);
imagefill($tmp_img, 0, 0, $white);
imagecopyresampled($tmp_img, $img, 0, 0, 0, 0, $target_width, $target_height, $raw_x, $raw_y);
$img = $tmp_img;