从零构建图片编辑应用：Swift实现图片选择功能详解

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从零构建图片编辑应用：Swift实现图片选择功能详解

引用

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来源

https://blog.csdn.net/kicinio/article/details/118247125

https://swiftsenpai.com/development/photo-library-permission/

https://developer.apple.com/documentation/uikit/uiimagepickercontroller

https://developer.apple.com/documentation/uikit/customizing-an-image-picker-controller

https://www.hangge.com/blog/cache/detail_1512.html

https://developer.aliyun.com/article/57185

在移动应用开发中，图片选择功能是最常见的需求之一。本文将介绍如何使用Swift和UIKit实现这一功能，并探讨在线图片编辑软件（如Pixso）的优势。

使用Swift和UIKit实现图片选择功能

从相册选择图片

要实现从相册选择图片的功能，我们需要使用UIImagePickerController。首先，确保在info.plist文件中添加了NSPhotoLibraryUsageDescription键，用于描述应用程序为什么需要访问照片库。

接下来，在ViewController中实现以下代码：

import UIKit

class ImageViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    var buttonSelect: UIButton!
    var imageView: UIImageView!

    private func initView(){
        buttonSelect = UIButton(type: .system)
        buttonSelect.setTitle("Select", for: UIControl.State.normal)
        buttonSelect.frame = CGRect(x: ((self.view.frame.width / 2) - 35), y: (self.view.frame.width - 200), width: 70, height: 30)
        buttonSelect.addTarget(self, action: #selector(selectPicture), for: UIControl.Event.touchDown)
        self.view.addSubview(buttonSelect)
        
        imageView = UIImageView(frame: CGRect(x: ((self.view.frame.width / 2) - 120), y: ((self.view.frame.height / 2) + 50), width: 240, height: 240))
        imageView.image = UIImage(named: "taylor")
        self.view.addSubview(imageView)
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        initView()
    }
    
    @objc func selectPicture(){
        if UIImagePickerController.isSourceTypeAvailable(.photoLibrary) {
            let pickerVC = UIImagePickerController()
            pickerVC.delegate = self
            pickerVC.sourceType = UIImagePickerController.SourceType.photoLibrary
            self.present(pickerVC, animated: true, completion: nil)
        } else {
            print("------> ERROR")
        }
    }
    
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {
        if let image = info[.originalImage] as? UIImage {
            self.imageView.image = image
        }
        picker.dismiss(animated: true, completion: nil)
    }
}

从相机选择图片

从相机选择图片的实现方式与从相册选择类似，只需要将sourceType设置为.camera即可。

@objc func selectPictureFromCamera(){
    if UIImagePickerController.isSourceTypeAvailable(.camera) {
        let pickerVC = UIImagePickerController()
        pickerVC.delegate = self
        pickerVC.sourceType = UIImagePickerController.SourceType.camera
        self.present(pickerVC, animated: true, completion: nil)
    } else {
        print("Camera is not available")
    }
}

iOS 14及更高版本的照片库权限处理

在iOS 14及更高版本中，苹果引入了有限照片访问权限，用户可以选择只允许应用访问部分照片。这要求开发者必须正确处理各种权限状态。

首先需要在info.plist中添加NSPhotoLibraryUsageDescription键。然后在代码中请求权限：

import PhotosUI

override func viewDidLoad() {
    super.viewDidLoad()
    PHPhotoLibrary.requestAuthorization(for: .readWrite) { [unowned self] (status) in
        DispatchQueue.main.async { [unowned self] in
            showUI(for: status)
        }
    }
}

注意：请求完成处理程序不在主线程上运行，因此在更新视图时需要切换回主线程。