ConsoleUI
Demo repository to showcase how to programmatically generate images from a command-line tool with SwiftUI.
The Basics: Hello, world!
Create a new command-line executable
$ mkdir mytool && cd mytool
$ swift package init --type executable
$ swift run
Hello, world!
Generate Xcode project (optional)
Xcode does not support live previews on Swift packages yet (FB8979344). To allow for realtime previews follow these steps:
- Generate an Xcode project
- Add a macOS target to the project
- Add your view (see next section) to the macOS target
$ swift package generate-xcodeproj
$ open mytool.xcodeproj
Add SwiftUI view
Create a view with a red label over white background
import SwiftUI
struct MySwiftUIView : View {
var body: some View {
ZStack {
Color.blue.edgesIgnoringSafeArea(.all)
Text("Hello, world!")
.foregroundColor(.white)
.font(.largeTitle)
}
}
}
#if DEBUG
struct MySwiftUIView_Previews : PreviewProvider {
static var previews: some View {
MySwiftUIView()
}
}
#endif
Rasterize view and save to file
We will use this method to rasterize views to images:
func rasterize(view: NSView, format: NSBitmapImageRep.FileType) -> Data? {
guard let bitmapRepresentation = view.bitmapImageRepForCachingDisplay(in: view.bounds) else {
return nil
}
bitmapRepresentation.size = view.bounds.size
view.cacheDisplay(in: view.bounds, to: bitmapRepresentation)
return bitmapRepresentation.representation(using: format, properties: [:])
}The following code instantiates the SwiftUI view, wrapped inside a NSHostingView which is then
rasterized and saved to disk
let wrapper = NSHostingView(rootView: MySwiftUIView())
wrapper.frame = CGRect(x: 0, y: 0, width: 800, height: 450)
let png = rasterize(view: wrapper, format: .png)
try png?.write(to: URL(fileURLWithPath: "test.png"))
Run the command and open in Preview
$ swift run && open test.png
