Screenshot Capture Testing

Cross-platform screenshot capture for visual testing, UI verification, and automated comparison. Supports full screen, specific app/window, and pixel region captures.

Tool Priority

• Prefer tool-specific screenshot capabilities when available (Playwright for browsers, Figma MCP for designs)
• Use this skill for whole-system desktop captures or when tool-specific capture cannot get what you need
• Default for desktop apps without a better-integrated capture tool

macOS Capture

Full screen

screencapture -x output/screen.png

Pixel region (x,y,w,h)

screencapture -x -R100,200,800,600 output/region.png

Specific window by ID

screencapture -x -l12345 output/window.png

Interactive selection

screencapture -x -i output/interactive.png

Linux Capture

Using scrot

# Full screen
scrot output/screen.png

# Pixel region
scrot -a 100,200,800,600 output/region.png

# Active window
scrot -u output/window.png

Using gnome-screenshot

gnome-screenshot -f output/screen.png
gnome-screenshot -w -f output/window.png

Using ImageMagick

import -window root output/screen.png
import -window root -crop 800x600+100+200 output/region.png

Windows Capture (PowerShell)

# Full screen
powershell -ExecutionPolicy Bypass -File take_screenshot.ps1

# Pixel region
powershell -ExecutionPolicy Bypass -File take_screenshot.ps1 -Region 100,200,800,600

# Active window
powershell -ExecutionPolicy Bypass -File take_screenshot.ps1 -ActiveWindow

Visual Testing Workflow

1. Capture baseline — Take reference screenshots of correct UI state
2. Capture current — Take screenshots of current UI state after changes
3. Compare — Diff the screenshots to detect visual regressions
4. Report — Generate visual diff reports with highlighted changes

Multi-Display Behavior

• macOS: Full-screen captures save one file per display with multiple monitors
• Linux/Windows: Full-screen captures use virtual desktop (all monitors in one image)
• Use --region to isolate a single display when needed

Error Handling

• On macOS, check Screen Recording permission before window/app capture
• On Linux, verify tool availability: command -v scrot, command -v gnome-screenshot
• If saving fails with permission errors, check directory permissions
• Always report the saved file path in the response

Best Practices

• Use consistent viewport sizes for comparable screenshots
• Mask dynamic content (timestamps, animations) before comparison
• Set appropriate diff thresholds for anti-aliasing tolerance
• Store baseline screenshots in version control
• Run visual tests in consistent environments (same OS, resolution, DPI)