如何从 swift 中的 UIImage 获取图像 extension/format？

Question

我正在尝试将图片上传到我的服务器，但在上传之前，我需要检查它是否是有效格式。

假设我只想要 .jpeg 和 .png，所以如果用户从他们的 phone 中选择 .gif 格式的图像，我会显示一些警告。

我从用户那里得到图片gallery/camera，然后我想查看格式，但我不知道如何查看格式

@IBAction func selectPictureButtonDidPressed(_ sender: Any) {
    let imagePickerController = UIImagePickerController()
    imagePickerController.delegate = self
    imagePickerController.allowsEditing = true
    
    let actionSheet = UIAlertController(title: "Photo Source", message: "please choose your source", preferredStyle: .actionSheet)
    
    // action camera
    let actionCamera = UIAlertAction(title: "Camera", style: .default) { (action) in
        if UIImagePickerController.isSourceTypeAvailable(.camera) {
            imagePickerController.sourceType = .camera
            self.present(imagePickerController, animated: true, completion: nil)
        } else {
            self.showAlert(alertTitle: "Opppss", alertMessage: "camera can't be used / not available", actionTitle: "OK")
            print("camera can't be used / not available")
        }
    }
    
    // action photo library
    let actionPhotoLibrary = UIAlertAction(title: "Photo Library", style: .default) { (action) in
        imagePickerController.sourceType = .photoLibrary
        self.present(imagePickerController, animated: true, completion: nil)
    }
    
    //action cancel
    let actionCancel = UIAlertAction(title: "Cancel", style: .cancel, handler: nil)
    
    actionSheet.addAction(actionCamera)
    actionSheet.addAction(actionPhotoLibrary)
    actionSheet.addAction(actionCancel)
    
    self.present(actionSheet, animated: true, completion: nil)
}

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
    let image = info[UIImagePickerControllerOriginalImage] as! UIImage
    postImage.image = image
    picker.dismiss(animated: true, completion: nil)
    
    doesItHasImage = true
}

func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
    picker.dismiss(animated: true, completion: nil)
}

如何检查该格式？

我试图在 google 上找到，但如果它是从 URL 派生的，我只能得到图像格式。不是像这样直接来自 UIImage

import UIKit
import ImageIO

struct ImageHeaderData{
    static var PNG: [UInt8] = [0x89]
    static var JPEG: [UInt8] = [0xFF]
    static var GIF: [UInt8] = [0x47]
    static var TIFF_01: [UInt8] = [0x49]
    static var TIFF_02: [UInt8] = [0x4D]
}

enum ImageFormat{
    case Unknown, PNG, JPEG, GIF, TIFF
}

extension NSData{
    var imageFormat: ImageFormat{
        var buffer = [UInt8](repeating: 0, count: 1)
        self.getBytes(&buffer, range: NSRange(location: 0,length: 1))
        if buffer == ImageHeaderData.PNG
        {
            return .PNG
        } else if buffer == ImageHeaderData.JPEG
        {
            return .JPEG
        } else if buffer == ImageHeaderData.GIF
        {
            return .GIF
        } else if buffer == ImageHeaderData.TIFF_01 || buffer == ImageHeaderData.TIFF_02{
            return .TIFF
        } else{
            return .Unknown
        }
    }
}

// USAGE
let imageURLFromParse = NSURL(string : "https://i.stack.imgur.com/R64uj.jpg")
let imageData = NSData(contentsOf: imageURLFromParse! as URL)
print(imageData!.imageFormat)

Answer 1

您需要将图像覆盖为原始数据，可能使用 UIImagePNGRepresentation() 或 UIImageJPEGRepresentation()，然后将其发送到您的服务器。该数据将分别采用 PNG 或 JPEG 格式。

Answer 2

你可以试试这个：

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])
{
    let assetPath = info[UIImagePickerControllerReferenceURL] as! NSURL
    if (assetPath.absoluteString?.hasSuffix("JPG"))! {
        print("JPG")
    }
    else if (assetPath.absoluteString?.hasSuffix("PNG"))! {
        print("PNG")
    }
    else if (assetPath.absoluteString?.hasSuffix("GIF"))! {
        print("GIF")
    }
    else {
        print("Unknown")
    }
}

Answer 3

如果首选使用 URL，在 swift 5.2 中您可以使用

enum ImageFormat {
    case png
    case jpeg
    case gif
    case tiff
    case unknown
    
    init(byte: UInt8) {
        switch byte {
        case 0x89:
            self = .png
        case 0xFF:
            self = .jpeg
        case 0x47:
            self = .gif
        case 0x49, 0x4D:
            self = .tiff
        default:
            self = .unknown
        }
    }
}

extension Data {
    var imageFormat: ImageFormat{
        guard let header = map({ [=10=] as UInt8 })[safe: 0] else {
            return .unknown
        }
        
        return ImageFormat(byte: header)
    }
}

extension Collection {
    
    /// Returns the element at the specified index iff it is within bounds, otherwise nil.
    /// - Parameters:
    ///   - Parameter index: The index of the item to get safely the element
    /// - Returns: The element if available or nil otherwise
    subscript(safe index: Index) -> Element? {
        return indices.contains(index) ? self[index] : nil
    }
    
}

我发现：

jpegData(compressionQuality: CGFloat)
pngData()

总是成功，而且内存效率不高。在一个案例中，我看到一张 1.6Mb 的图像变成了 6MB 只是因为 pngData()

Answer 4

更新代码：

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {

    guard let image = info[.editedImage] as? UIImage else { return }

    if let assetPath = info[.imageURL] as? URL{
        let URLString = assetPath.absoluteString.lowercased()
        if (URLString.hasSuffix("jpg")) {
            print("JPG")
            uploadedImage = image
            uploadImage(type: ImageTypes.JPG)
        }
        else if (URLString.hasSuffix("jpeg")) {
            print("JPEG")
        }
        else if (URLString.hasSuffix("png")) {
            print("PNG")
        }
        else {
            print("Invalid Type")
        }
    }
    dismiss(animated: true)
}

如何从 swift 中的 UIImage 获取图像 extension/format？

How to get Image extension/format from UIImage in swift?

uiimagepickercontroller

uiimage

nsdata

ios

swift