GreenshotMac

A native, Apple-silicon macOS screenshot tool modelled on Greenshot for Windows. Written in Swift with AppKit, SwiftUI and ScreenCaptureKit — no Mono, no Wine, no .NET runtime.

The original C# sources are kept in reference-greenshot/ purely as the behavioural reference for the port. GreenshotMac is a rewrite, not a transpile: Greenshot's Win32 foundations (GDI+, WinForms, RegisterHotKey, the shell tray API) have no direct macOS counterparts.

Requirements

• macOS 14 (Sonoma) or later
• Xcode 16 or later
• Apple silicon (the target builds arm64 only)

Building

open GreenshotMac.xcodeproj      # then ⌘R
# or
xcodebuild -project GreenshotMac.xcodeproj -scheme GreenshotMac -configuration Release build

The target is configured for ad-hoc signing (CODE_SIGN_IDENTITY = "-") so it builds without a developer account. Set your own team in Signing & Capabilities if you want a stable signature — macOS ties Screen Recording permission to the signature, so an ad-hoc build may ask for permission again after some rebuilds.

On first launch macOS asks for Screen Recording permission (System Settings › Privacy & Security › Screen Recording). Nothing can be captured until it is granted.

Using it

GreenshotMac is a menu bar app (LSUIElement), so it has no Dock icon. The camera icon in the menu bar holds every command.

Default global hotkeys — Greenshot's PrintScreen-based defaults don't exist on a Mac keyboard, so these use combinations macOS leaves free:

Action	Shortcut
Capture region	⌥⇧⌘4
Capture full screen	⌥⇧⌘3
Capture window	⌥⇧⌘5
Capture last region	⌥⇧⌘6

All four are re-recordable in Preferences › Hotkeys.

During a capture the desktop freezes under a dimmed overlay: drag to select a region, press Space to switch to window mode and click a window, Esc to cancel. A magnifier and a live pixel-size readout follow the cursor.

Editor

Tool	Key
Select	V
Rectangle / Ellipse	R / E
Line / Arrow	L / A
Freehand	F
Text	T
Highlight	H
Obfuscate (pixelate or blur)	O
Step counter	C
Crop	K

Shift constrains shapes to squares/circles and lines to 45° steps. Arrow keys nudge the selection (⇧ for 10 px steps). ⌘Z / ⇧⌘Z undo and redo, including crops.

Destinations

After a capture the destination picker appears: a preview of what you grabbed, one button per destination, ⌘1…⌘9 to pick from the keyboard, Esc to discard, and "Always use this destination" to skip the dialog next time. The buttons default to Edit / Save to Disk / Copy to Clipboard / Send as Mail, matching Greenshot.

The full destination set is clipboard, save with a filename pattern, Save As…, print, email, the macOS share sheet, and "open with". Set a destination as the default (skipping the picker) in Preferences › General, from the menu bar, or via the picker's checkbox.

Filename patterns use Greenshot's syntax, ported verbatim:

${capturetime:d"yyyy-MM-dd HH_mm_ss"}-${title}

Supported variables: ${capturetime}, ${now}, ${title}, ${appname}, ${user}, ${hostname}, ${mode}, ${NUM} (with :d4 for zero padding), plus the :t, :u, :l, :s, :r parameters.

How the port maps onto Greenshot

Greenshot (Windows)	GreenshotMac
MainForm + tray icon	StatusMenuController (NSStatusItem)
CaptureForm	CaptureOverlay (one borderless window per display)
WindowCapture / GDI+	CaptureEngine (ScreenCaptureKit)
HotkeyControl / RegisterHotKey	HotkeyManager (Carbon RegisterEventHotKey)
Surface + DrawableContainer	Surface + Element hierarchy
ImageEditorForm	EditorWindowController + EditorCanvasView
FilenameHelper	FilenamePattern
ImageIO	ImageExporter
IDestination implementations	Destinations
SettingsForm	PreferencesView (SwiftUI)
IniConfig / greenshot.ini	Configuration (UserDefaults)

Not ported

The plugin destinations (Imgur, Box, Dropbox, Confluence, Jira, Office, OCR, external command), the speech-bubble and SVG/emoji containers, .gst templates, and Greenshot's language packs. The destination layer is a single switch in Destinations.swift, so adding an upload target is a small, self-contained change.

Licence

Greenshot is GPL-3.0; this port keeps the same licence.