Image via Wikipedia

I’ve run into an error using an image resizing script by Victor Teixeira, which has worked wonderfully until I noticed an issue related to using the Featured Image uploader. If I a Featured Image, then attempt to re-insert a different image in its place I get this error:

function vt_resize( $attach_id = null, $img_url = null, $width, $height, $crop = false ) {

// this is an attachment, so we have the ID
if ( $attach_id ) {

    $image_src = wp_get_attachment_image_src( $attach_id, 'full' );
    $file_path = get_attached_file( $attach_id );

// this is not an attachment, let's use the image url
} else if ( $img_url ) {

    $file_path = parse_url( $img_url );
    $file_path = $_SERVER['DOCUMENT_ROOT'] . $file_path['path'];

    //$file_path = ltrim( $file_path['path'], '/' );
    //$file_path = rtrim( ABSPATH, '/' ).$file_path['path'];

    $orig_size = getimagesize( $file_path );

    $image_src[0] = $img_url;
    $image_src[1] = $orig_size[0];
    $image_src[2] = $orig_size[1];
}

$file_info = pathinfo( $file_path );
$extension = '.'. $file_info['extension'];

// the image path without the extension
$no_ext_path = $file_info['dirname'].'/'.$file_info['filename'];

$cropped_img_path = $no_ext_path.'-'.$width.'x'.$height.$extension;

// checking if the file size is larger than the target size
// if it is smaller or the same size, stop right here and return
if ( $image_src[1] > $width || $image_src[2] > $height ) {

    // the file is larger, check if the resized version already exists (for $crop = true but will also work for $crop = false if the sizes match)
    if ( file_exists( $cropped_img_path ) ) {

        $cropped_img_url = str_replace( basename( $image_src[0] ), basename( $cropped_img_path ), $image_src[0] );

        $vt_image = array (
            'url' => $cropped_img_url,
            'width' => $width,
            'height' => $height
        );

        return $vt_image;
    }

    // $crop = false
    if ( $crop == false ) {

        // calculate the size proportionaly
        $proportional_size = wp_constrain_dimensions( $image_src[1], $image_src[2], $width, $height );
        $resized_img_path = $no_ext_path.'-'.$proportional_size[0].'x'.$proportional_size[1].$extension;            

        // checking if the file already exists
        if ( file_exists( $resized_img_path ) ) {

            $resized_img_url = str_replace( basename( $image_src[0] ), basename( $resized_img_path ), $image_src[0] );

            $vt_image = array (
                'url' => $resized_img_url,
                'width' => $proportional_size[0],
                'height' => $proportional_size[1]
            );

            return $vt_image;
        }
    }

    // no cache files - let's finally resize it
    $new_img_path = image_resize( $file_path, $width, $height, $crop );
    $new_img_size = getimagesize( $new_img_path );
    $new_img = str_replace( basename( $image_src[0] ), basename( $new_img_path ), $image_src[0] );

    // resized output
    $vt_image = array (
        'url' => $new_img,
        'width' => $new_img_size[0],
        'height' => $new_img_size[1]
    );

    return $vt_image;
}

// default output - without resizing
$vt_image = array (
    'url' => $image_src[0],
    'width' => $image_src[1],
    'height' => $image_src[2]
);

return $vt_image;
}