The SwiftUI Playground code below demonstrates that a .jpeg image can be read and written to the iOS file system. While, a.png image can only be read; the writing request appears to be ignored. Can anyone please tell me how to code to save a .png image using SwiftUI to the iOS file system.
Code:
import SwiftUI
import UniformTypeIdentifiers
/*
(Copied from Playground 'Help' menu popup.)
UIImage Summary
An object that manages image data in your app.
You use image objects to represent image data of all kinds, and the UIImage class is capable of managing data for all image formats supported by the underlying platform. Image objects are immutable, so you always create them from existing image data, such as an image file on disk or programmatically created image data. An image object may contain a single image or a sequence of images for use in an animation.
You can use image objects in several different ways:
Assign an image to a UIImageView object to display the image in your interface.
Use an image to customize system controls such as buttons, sliders, and segmented controls.
Draw an image directly into a view or other graphics context.
Pass an image to other APIs that might require image data.
Although image objects support all platform-native image formats, it’s recommended that you use PNG or JPEG files for most images in your app. Image objects are optimized for reading and displaying both formats, and those formats offer better performance than most other image formats. Because the PNG format is lossless, it’s especially recommended for the images you use in your app’s interface.
Declaration
class UIImage : NSObject
UIImage Class Reference
*/
@main
struct MyApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
struct ImageFileDoc: FileDocument {
static var readableContentTypes = [UTType.jpeg, UTType.png]
static var writableContentTypes = [UTType.jpeg, UTType.png]
var someUIImage: UIImage = UIImage()
init(initialImage: UIImage = UIImage()) {
self.someUIImage = initialImage
}
init(configuration: ReadConfiguration) throws {
guard let data = configuration.file.regularFileContents,
let some = UIImage(data: data)
else {
throw CocoaError(.fileReadCorruptFile)
}
self.someUIImage = some
}
func fileWrapper(configuration: WriteConfiguration) throws -> FileWrapper {
switch configuration.contentType {
case UTType.png:
if let data = self.someUIImage.pngData() {
return .init(regularFileWithContents: data)
}
case UTType.jpeg:
if let data = self.someUIImage.jpegData(compressionQuality: 1.0) {
return .init(regularFileWithContents: data)
}
default:
break
}
throw CocoaError(.fileWriteUnknown)
}
}
struct ContentView: View {
@State private var showingExporterPNG = false
@State private var showingExporterJPG = false
@State private var showingImporter = false
@State var message = "Hello, World!"
@State var document: ImageFileDoc = ImageFileDoc()
@State var documentExtension = ""
var body: some View {
VStack {
Image(systemName: "globe")
.imageScale(.large)
.foregroundColor(.accentColor)
Text(message)
Button("export") {
if documentExtension == "png" {
message += ", showingExporterPNG is true."
showingExporterPNG = true
}
if documentExtension == "jpeg" {
message += ", showingExporterJPG is true."
showingExporterJPG = true
}
}
.padding(20)
.border(.white, width: 2.0)
.disabled(documentExtension == "")
Button("import") {
showingImporter = true
}
.padding(20)
.border(.white, width: 2.0)
Image(uiImage: document.someUIImage)
.resizable()
.padding()
.frame(width: 300, height: 300)
}
// exporter .png
.fileExporter(isPresented: $showingExporterPNG, document: document, contentType: UTType.png) { result in
switch result {
case .success(let url):
message += ", .\(documentExtension) Saved to \(url.lastPathComponent)"
case .failure(let error):
message += ", Some error saving file: " + error.localizedDescription
}
}
// exporter .jpeg
.fileExporter(isPresented: $showingExporterJPG, document: document, contentType: UTType.jpeg) { result in
switch result {
case .success(let url):
message += ", .\(documentExtension) Saved to \(url.lastPathComponent)"
case .failure(let error):
message += ", Some error saving file: " + error.localizedDescription
}
}
// importer
.fileImporter(isPresented: $showingImporter, allowedContentTypes: [.png, .jpeg]) { result in
switch result {
case .failure(let error):
message += ", Some error reading file: " + error.localizedDescription
case .success(let url):
let gotAccess = url.startAccessingSecurityScopedResource()
if !gotAccess {
message += ", Unable to Access \(url.lastPathComponent)"
return
}
documentExtension = url.pathExtension
guard let fileContents = try? Data(contentsOf: url)
else {
message += ",\n\nUnable to read file: \(url.lastPathComponent)\n\n"
url.stopAccessingSecurityScopedResource()
return
}
url.stopAccessingSecurityScopedResource()
message += ", Read file: \(url.lastPathComponent)"
message += ", path extension is '\(documentExtension)'."
if let uiImage = UIImage(data: fileContents) {
self.document.someUIImage = uiImage
}else{
message += ", File Content is not an Image."
}
}
}
}
}
