Swift 使用jpegData（compressionQual

图像表示将占用大量的CPU和内存资源。 因此，在这种情况下，最好遵循以下几条规则：

• 不要在主队列上运行jpegData（compressionQuality :)

• 同时运行一个jpegData（compressionQuality :)

错误：

for i in 0...50 {
    DispatchQueue.global(qos: .utility).async {
        let quality = 0.02 * CGFloat(i)
        //let data = image.toJpegData(compressionQuality: quality)
        let data = image.jpegData(compressionQuality: quality)
        let size = CGFloat(data!.count)/1000.0/1024.0
        print("\(i), quality: \(quality), \(size.rounded()) mb")
    }
}

正确

let serialQueue = DispatchQueue(label: "queue", qos: .utility, attributes: [], autoreleaseFrequency: .workItem, target: nil)

for i in 0...50 {
    serialQueue.async {
        let quality = 0.02 * CGFloat(i)
        //let data = image.toJpegData(compressionQuality: quality)
        let data = image.jpegData(compressionQuality: quality)
        let size = CGFloat(data!.count)/1000.0/1024.0
        print("\(i), quality: \(quality), \(size.rounded()) mb")
    }
}

原文地址：https://www.itranslater.com/qa/details/2325693309395665920