iPhoto had 6 “killer” features:
• Smart Browsing
• Multi-Touch Editing
• Professional-Quality Effects
• Brushes
• Photo Journals
• Sharing
In the interest of brevity, we’ll focus on just the five editing tools: crop, exposure, color, brushes, and auto-enhance.
Cropping is the most straightforward. You pinch and zoom to crop, there are some preset constraints under the gear button menu.
If iPhoto detects something resembling a horizon line, it’ll show a line flanked by some extremely period-correct radial brushed metal buttons to either accept or reject the changes. Today, building this would’ve been significantly easier with the nifty VNHorizonObservation class in the Vision framework.