Saving a transparent image from a URL in PHP

I am trying to build a class that does many photo operations, one method will upload images from a user but I am also needing to build a method to grab a photo from a URL and run other methods on it just like if it were being uploaded with a POST form from user.

Below is my start of the function for getting image from URL, it works but needs work still. Below the code you can see a image that is the result of th开发者_如何学JAVAis function being ran. Also is the original image to see what it should look like. You can see that this function makes the image have a black background on this transparent image. How can I make it look better like it should look?

$url = 'http://a0.twimg.com/a/1262802780/images/twitter_logo_header.png';

//run our function
savePhotofromURL($url, 'no');



// photo function should grab an photo from a URL
function savePhotofromURL($photo_url, $saveimage = 'yes'){
    if(isset($photo_url) && $photo_url != '') {

        //get info about photo
        $photo_info = getimagesize($photo_url);
        $source_width = $photo_info['0'];
        $source_height = $photo_info['1'];
        $source_type = $photo_info['mime'];

        //grab the Photo from URL
        $photo = imagecreatefromstring(file_get_contents($photo_url));

        if (is_resource($photo) === true){
            if($saveimage === 'yes'){
                // TO DO: resize image and make the thumbs code would go here if we are saving image:
                // TO DO: resize source image if it is wider then 800 pixels
                // TO DO: make 1 thumbnail that is 150 pixels wide
            }else{
                // We are not saving the image show it in the user's browser
                // TO DO: we will add in correct photo type soon
                header('Content-Type: image/gif');
                imagejpeg($photo, null, 100);
                imagedestroy($photo); 
            }
        }else{
            // not a valid resource, show error
            echo 'error getting URL photo from ' .$photo_url;
        }
    }else{
        // url of image was empty
        echo 'The URL was not passed into our function';
    }
}

The result looks like this

alt text http://img2.pict.com/52/05/1f/2429493/0/screenshot2b181.png

Instead of like this

The following two calls will tell php to use the alpha blending present in the png image:

        ImageAlphaBlending($photo, false);
        ImageSaveAlpha($photo, true);

Edit: I see you're outputting the image as a JPEG also. JPEGs don't support transparency, so no matter what you do you will end up with an incorrect background color. Also see this related question: PHP/GD ImageSaveAlpha and ImageAlphaBlending

You need to add better support for image types and by extension their transparency.

Since the image is transparent we can know that its either a GIF or a PNG yet your sending the GIF header while using imagejpeg() - jpegs dont support any kind of transparency. But if its a png you may also have to account for if its alpha trans or index transparency.