View/Helper/GalleryHelper.php
public function cover($model = null, $model_id = null, $album_id = null, $style = 'medium')
    {
        if ($album = $this->getAlbum($model, $model_id, $album_id)) {
            if (!empty($album['Picture'][0])) {
                return '<img src="' . $album['Picture'][0]['styles'][$style] . '" alt="">';
            }
        }
    }
public function cover($model = null, $model_id = null, $album_id = null, $style = 'medium')
    {
        if ($album = $this->getAlbum($model, $model_id, $album_id)) {
            if (!empty($album['Picture'][0])) {
                return '<img src="' . $album['Picture'][0]['styles'][$style] . '" alt="">';
            }
        }
    }
Get cover picture from an album (The first picture)

@example
<?php echo $this->Gallery->cover('product', 10) ?>

@param null $model
@param null $model_id
@param null $album_id
@param string $style
@return string