屏幕截图
capture-screen
by daymade
在 macOS 上用 Swift 定位窗口 ID,配合 AppleScript 控制缩放、滚动与选区,再用 screencapture 批量截取应用窗口,适合文档配图和多步骤视觉流程自动化。
想把 macOS 截图流程自动化,它能精确定位窗口并用 AppleScript 联动操作,做文档截图和多步视觉采集尤其顺手。
安装
claude skill add --url github.com/daymade/claude-code-skills/tree/main/capture-screen文档
Capture Screen
Programmatic screenshot capture on macOS: find windows, control views, capture images.
Quick Start
# Find Excel window ID
swift scripts/get_window_id.swift Excel
# Capture that window (replace 12345 with actual WID)
screencapture -x -l 12345 output.png
Overview
Three-step workflow:
1. Find Window → Swift CGWindowListCopyWindowInfo → get numeric Window ID
2. Control View → AppleScript (osascript) → zoom, scroll, select
3. Capture → screencapture -l <WID> → PNG/JPEG output
Step 1: Get Window ID (Swift)
Use Swift with CoreGraphics to enumerate windows. This is the only reliable method on macOS.
Quick inline execution
swift -e '
import CoreGraphics
let keyword = "Excel"
let list = CGWindowListCopyWindowInfo(.optionOnScreenOnly, kCGNullWindowID) as? [[String: Any]] ?? []
for w in list {
let owner = w[kCGWindowOwnerName as String] as? String ?? ""
let name = w[kCGWindowName as String] as? String ?? ""
let wid = w[kCGWindowNumber as String] as? Int ?? 0
if owner.localizedCaseInsensitiveContains(keyword) || name.localizedCaseInsensitiveContains(keyword) {
print("WID=\(wid) | App=\(owner) | Title=\(name)")
}
}
'
Using the bundled script
swift scripts/get_window_id.swift Excel
swift scripts/get_window_id.swift Chrome
swift scripts/get_window_id.swift # List all windows
Output format: WID=12345 | App=Microsoft Excel | Title=workbook.xlsx
Parse the WID number for use with screencapture -l.
Step 2: Control Window (AppleScript)
Verified commands for controlling application windows before capture.
Microsoft Excel (full AppleScript support)
# Activate (bring to front)
osascript -e 'tell application "Microsoft Excel" to activate'
# Set zoom level (percentage)
osascript -e 'tell application "Microsoft Excel"
set zoom of active window to 120
end tell'
# Scroll to specific row
osascript -e 'tell application "Microsoft Excel"
set scroll row of active window to 45
end tell'
# Scroll to specific column
osascript -e 'tell application "Microsoft Excel"
set scroll column of active window to 3
end tell'
# Select a cell range
osascript -e 'tell application "Microsoft Excel"
select range "A1" of active sheet
end tell'
# Select a specific sheet
osascript -e 'tell application "Microsoft Excel"
activate object sheet "DCF" of active workbook
end tell'
# Open a file
osascript -e 'tell application "Microsoft Excel"
open POSIX file "/path/to/file.xlsx"
end tell'
Any application (basic control)
# Activate any app
osascript -e 'tell application "Google Chrome" to activate'
# Bring specific window to front (by index)
osascript -e 'tell application "System Events"
tell process "Google Chrome"
perform action "AXRaise" of window 1
end tell
end tell'
Timing and Timeout
Always add sleep 1 after AppleScript commands before capturing, to allow UI rendering to complete.
IMPORTANT: osascript hangs indefinitely if the target application is not running or not responding. Always wrap with timeout:
timeout 5 osascript -e 'tell application "Microsoft Excel" to activate'
Step 3: Capture (screencapture)
# Capture specific window by ID
screencapture -l <WID> output.png
# Silent capture (no camera shutter sound)
screencapture -x -l <WID> output.png
# Capture as JPEG
screencapture -l <WID> -t jpg output.jpg
# Capture with delay (seconds)
screencapture -l <WID> -T 2 output.png
# Capture a screen region (interactive)
screencapture -R x,y,width,height output.png
Retina displays
On Retina Macs, screencapture outputs 2x resolution by default (e.g., a 2032x1238 window produces a 4064x2476 PNG). This is normal. To get 1x resolution, resize after capture:
sips --resampleWidth 2032 output.png --out output_1x.png
Verify capture
# Check file was created and has content
ls -la output.png
file output.png # Should show "PNG image data, ..."
Multi-Shot Workflow
Complete example: capture multiple sections of an Excel workbook.
# 1. Open file and activate Excel
osascript -e 'tell application "Microsoft Excel"
open POSIX file "/path/to/model.xlsx"
activate
end tell'
sleep 2
# 2. Set up view
osascript -e 'tell application "Microsoft Excel"
set zoom of active window to 130
activate object sheet "Summary" of active workbook
end tell'
sleep 1
# 3. Get window ID
# IMPORTANT: Always re-fetch before capturing. CGWindowID is invalidated
# when an app restarts or a window is closed and reopened.
WID=$(swift -e '
import CoreGraphics
let list = CGWindowListCopyWindowInfo(.optionOnScreenOnly, kCGNullWindowID) as? [[String: Any]] ?? []
for w in list {
let owner = w[kCGWindowOwnerName as String] as? String ?? ""
let wid = w[kCGWindowNumber as String] as? Int ?? 0
if owner == "Microsoft Excel" { print(wid); break }
}
')
echo "Window ID: $WID"
# 4. Capture Section A (top of sheet)
osascript -e 'tell application "Microsoft Excel"
set scroll row of active window to 1
end tell'
sleep 1
screencapture -x -l $WID section_a.png
# 5. Capture Section B (further down)
osascript -e 'tell application "Microsoft Excel"
set scroll row of active window to 45
end tell'
sleep 1
screencapture -x -l $WID section_b.png
# 6. Switch sheet and capture
osascript -e 'tell application "Microsoft Excel"
activate object sheet "DCF" of active workbook
set scroll row of active window to 1
end tell'
sleep 1
screencapture -x -l $WID dcf_overview.png
Failed Approaches (DO NOT USE)
These methods were tested and confirmed to fail on macOS:
| Method | Error | Why It Fails |
|---|---|---|
System Events → id of window | Error -1728 | System Events cannot access window IDs in the format screencapture needs |
Python import Quartz (PyObjC) | ModuleNotFoundError | PyObjC not installed in system Python; don't attempt to install it — use Swift instead |
osascript window id | Wrong format | Returns AppleScript window index, not CGWindowID needed by screencapture -l |
Supported Applications
| Application | Window ID | AppleScript Control | Notes |
|---|---|---|---|
| Microsoft Excel | Swift | Full (zoom, scroll, select, activate sheet) | Best supported |
| Google Chrome | Swift | Basic (activate, window management) | No scroll/zoom via AppleScript |
| Any macOS app | Swift | Basic (activate via tell application) | screencapture works universally |
AppleScript control depth varies by application. Excel has the richest AppleScript dictionary. For apps with limited AppleScript, use keyboard simulation via System Events as a fallback.
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