如何提高UIImage到UIImageView的性能？

Question

我有UITableView和UITableViewCell，它包含6个UIImageView：2（140x140）和4个（18x18）以及其他一些视图。

我还使用了所有最佳实践，例如：

• dequeueReusableCell;
• 没有阻止主线程;
• 使用不透明视图;
• 在设置为UIImageView之前调整图像大小。

但我的iPad滚动性能有问题。有6个可见细胞（iPad专业版9.7），滚动性能非常糟糕。我发现，当我评论设置图像滚动效果非常好，所以，图像的问题。此外，我使用Time Profiler并检测到我的代码运行速度很快，但在设置图像时系统库会做很多工作。

那么，有没有办法改善设置和滚动性能？

func setImage(from string: String?, to view: UIImageView) {
        DispatchQueue(label: "com.myCompany.image-converter", qos: .userInitiated).async {
            let imageData = Data(base64Encoded: string ?? "", options: Data.Base64DecodingOptions(rawValue: 0))
            if let correctImageData = imageData {
                let sourceImage = UIImage(data: correctImageData)

                let size = CGSize(width: view.bounds.width, height: view.bounds.height)
                let rect = CGRect(x: 0, y: 0, width: size.width, height: size.height)

                UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
                sourceImage?.draw(in: rect)
                let resizedImage = UIGraphicsGetImageFromCurrentImageContext()
                UIGraphicsEndImageContext()

                DispatchQueue.main.async {
                    view.image = resizedImage
                }
            }
        }
    }

在这里，我调用自定义UITableViewCell中的update方法设置图像。

DispatchQueue.global(qos: .userInitiated).async {
            let imageConverter = ImageBase64Converter()
            imageConverter.setImage(from: contest.contestPlayerOne.player.image, to: self.leftPlayerImageView)
            imageConverter.setImage(from: contest.contestPlayerTwo.player.image, to: self.rightPlayerImageView)
            imageConverter.setImage(from: contest.contestPlayerOne.schedule.teamHome.image, to: self.leftTeamLeftPlayerImageView)
            imageConverter.setImage(from: contest.contestPlayerOne.schedule.teamAway.image, to: self.rightTeamLeftPlayerImageView)
            imageConverter.setImage(from: contest.contestPlayerTwo.schedule.teamHome.image, to: self.leftTeamRightPlayerImageView)
            imageConverter.setImage(from: contest.contestPlayerTwo.schedule.teamAway.image, to: self.rightTeamRightPlayerImageView)
        }