    func assetPortraitCellSize(forViewSize size: CGSize) -> CGSize {
        let count = CGFloat(assetPortraitColumnCount)
        let edge = (size.width - (count - 1) * assetPortraitInteritemSpace) / count
        return CGSize(width: edge, height: edge)
    }
    
    open var assetLandscapeColumnCount: Int = 7
    open var assetLandscapeInteritemSpace: CGFloat = 1.5
    open var assetLandscapeLineSpace: CGFloat = 1.5