ios - 有没有办法检查 UIImage 是否已解压缩？

Question

我相信你们中的大多数人都在后台线程上处理过强制解压以提高渲染性能。我的问题是是否有办法检查图像是否已解压缩。

Answer 1

它帮助我通过以下技术检查图像是否已解压缩。这是易于理解的简单代码：-

import UIKit
    class ViewController: UIViewController {
        var compressedImage:NSString?
        var decompressedImage:NSString?

        override func viewDidLoad() {
            super.viewDidLoad()

            let image = compressImage()
            var imageView = UIImageView(image: image)
            //self.view.addSubview(imageView)

          let decompressImage = deCompressImage(image: image)
            let imageData =  Data(UIImagePNGRepresentation(decompressImage)! )
            print("*****  Size after decompred \(imageData.description) **** ")
            imageView = UIImageView(image: decompressImage)
            decompressedImage = imageData.description as NSString?

            let decompressed = checkImageBeenDecompressed(decompressedImage: decompressedImage!, compressedImage: compressedImage!)
            print(decompressed)
                   //self.view.addSubview(imageView)

        }

        override func didReceiveMemoryWarning() {
            super.didReceiveMemoryWarning()
            // Dispose of any resources that can be recreated.
        }


        func checkImageBeenDecompressed(decompressedImage:NSString , compressedImage:NSString) -> Bool {
             let decompressedSize  = Int( decompressedImage.getNumFromString()! )
             let  compressedSize  =   Int (compressedImage.getNumFromString()! )
             if( decompressedSize!  >  compressedSize! ) {
                print("Image has been decompressed")
               return true
            }
            print("Image has not been decompressed")
            return false
        }


        func compressImage() -> UIImage {

            let oldImage = UIImage(named: "background.jpg")
            var imageData =  Data(UIImagePNGRepresentation(oldImage!)! )
            print("***** Original Uncompressed Size \(imageData.description) **** ")
            imageData = UIImageJPEGRepresentation(oldImage!, 0.025)!
            print("***** Compressed Size \(imageData.description) **** ")
            compressedImage = imageData.description as NSString?
            let image = UIImage(data: imageData)
            return image!
        }


        func deCompressImage(image:UIImage) -> UIImage {
            UIGraphicsBeginImageContextWithOptions(image.size, true, 0)
            image.draw(at: CGPoint.zero)
            let decompressedImage = UIGraphicsGetImageFromCurrentImageContext()
            UIGraphicsEndImageContext()
            return decompressedImage!
            }

    }


    extension NSString {
        func getNumFromString() -> String? {
            var numberString: NSString?
            let thisScanner = Scanner(string: self as String)
            let numbers = NSCharacterSet(charactersIn: "0123456789")
            thisScanner.scanUpToCharacters(from: numbers as CharacterSet, into: nil)
            thisScanner.scanCharacters(from: numbers as CharacterSet, into: &numberString)
            return numberString as? String;
        }
    }

演示参考