example by window capture

capture.swift

// origanl code : https://stackoverflow.com/questions/78846311/screencapturekit-example-in-go-c

import Foundation
import ScreenCaptureKit
import CoreGraphics
import AppKit

func captureScreenshot(display: SCDisplay?, window: SCWindow, app: SCRunningApplication,completion: @escaping (NSImage?) -> Void) {

    let filter: SCContentFilter
    if let display = display {
        filter = SCContentFilter(display: display, including: [app], exceptingWindows: [])
    } else {
        filter = SCContentFilter()
    }
    
    let configuration = SCStreamConfiguration()
    configuration.showsCursor = true
    configuration.scalesToFit = false
    
    SCScreenshotManager.captureImage(contentFilter: filter, configuration: configuration) { image, error in
        if let error = error {
            print("Error capturing screenshot: \(error.localizedDescription)")
            completion(nil)
        } else if let image = image {

            let cropRect = CGRect(x: window.frame.origin.x, y: window.frame.origin.y, width: window.frame.width, height: window.frame.height)
            guard let croppedCGImage = image.cropping(to: cropRect) else { return}

            completion(NSImage(cgImage: croppedCGImage, size: NSSize( width: window.frame.width, height: window.frame.height)))
            //completion(NSImage(cgImage: image, size: NSSize(width: image.width, height: image.height)))
        } else {
            print("No image captured")
            completion(nil)
        }
    }
}

// Main execution
func main() {
    let semaphore = DispatchSemaphore(value: 0)
    Task {
        do {

            let content = try await SCShareableContent.current

            guard let runapp = content.applications.first(where: { $0.applicationName == "Safari" }) else {
                print("\nSafari is not running.")
                return
            }

            guard let app_window = content.windows.first(where: { 
                $0.owningApplication == runapp && 
                $0.title != nil && 
                !$0.title!.isEmpty 
            }) else {
                return
            }
            
            guard !content.displays.isEmpty else {
                print("No displays found")
                semaphore.signal()
                return
            }
            
            print("Available displays:")
            for (index, display) in content.displays.enumerated() {
                print("\(index + 1). \(display.displayID) - \(display.width)x\(display.height)")
            }
            print("Enter the number of the display to capture (or press Enter for main display):")
            let input = readLine()?.trimmingCharacters(in: .whitespacesAndNewlines)
            
            let selectedDisplay: SCDisplay?
            if let index = Int(input ?? ""), (1...content.displays.count).contains(index) {
                selectedDisplay = content.displays[index - 1]
            } else {
                selectedDisplay = content.displays.first
            }
            
            captureScreenshot(display: selectedDisplay, window: app_window, app: runapp) { image in
                if let image = image {
                    

                        let currentDirectoryURL = URL(fileURLWithPath: FileManager.default.currentDirectoryPath)
                        let fileURL = currentDirectoryURL.appendingPathComponent("screenshot.png")
                        
                        if let tiffData = image.tiffRepresentation,
                        let bitmapImage = NSBitmapImageRep(data: tiffData),
                        let pngData = bitmapImage.representation(using: .png, properties: [:]) {
                            do {
                                try pngData.write(to: fileURL)
                                print("Screenshot saved to: \(fileURL.path)")
                            } catch {
                                print("Error saving screenshot: \(error.localizedDescription)")
                            }
                        } else {
                            print("Error converting image to PNG data")
                        }
                } else {
                    print("Failed to capture screenshot")
                }
                semaphore.signal()
            }
        } catch {
            print("Error getting shareable content: \(error.localizedDescription)")
            semaphore.signal()
        }
    }
    
    semaphore.wait()
}

main()