如何在UITableViewRowAction图像中缩放图像以适合动态单元格高度

Question

我尝试自定义UITableViewRowAction按钮，因此我使用的是image而不是默认按钮。

我的问题是单元格高度是动态的，所以如果单元格的高度太大，UITableViewRowAction中的图像会重复！，如下所示：

那么如何保持图像始终居中，无论细胞高度如何？

我的代码是：

    func tableView(tableView: UITableView, editActionsForRowAtIndexPath indexPath: NSIndexPath) -> [UITableViewRowAction]? {

    //delete location 

    let deleteAction: UITableViewRowAction = UITableViewRowAction(style: UITableViewRowActionStyle.Default, title: "         ", handler: {(tableViewRowAction:UITableViewRowAction, index:NSIndexPath) -> Void in


        self.deleteFavouriteLocationFromList(indexPath.row)


    })


    let image:UIImage = UIImage(named: "delete_icon_cell")!
    image.imageWithRenderingMode(UIImageRenderingMode.Automatic)

    let size = CGSizeApplyAffineTransform(image.size, CGAffineTransformMakeScale(0.29, 0.3))
    let hasAlpha = false
    let scale: CGFloat = 0.0 // Automatically use scale factor of main screen

    UIGraphicsBeginImageContextWithOptions(size, !hasAlpha, scale)
    image.drawInRect(CGRect(origin: CGPointZero, size: size))

    let scaledImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()


    deleteAction.backgroundColor = UIColor(patternImage: scaledImage)


    //edit location name

    let editAction: UITableViewRowAction = UITableViewRowAction(style: UITableViewRowActionStyle.Default, title: "         ", handler: {(tableViewRowAction:UITableViewRowAction, index:NSIndexPath) -> Void in


        self.presentEditFavouriteLocationNamePopUp(indexPath.row)


    })


    let editImage:UIImage = UIImage(named: "edit_icon_cell")!
    UIGraphicsBeginImageContextWithOptions(size, !hasAlpha, scale)
    editImage.drawInRect(CGRect(origin: CGPointZero, size: size))

    let editScaledImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    editAction.backgroundColor = UIColor(patternImage: editScaledImage)



    return [deleteAction,editAction]


}

感谢。