Cologne: A Day in Motion (Dynamic Wallpaper)

The Process

This project began with a single aerial photograph of Cologne. To bring it to life, I generated seven distinct lighting passes ranging from the deep blues of 2 AM, the beatiful sunrise, the bright mid-day sun of 11 AM, stunning sunset

• Image generation: I used Gemini with the 'Nanobana Pro' model to generate the frames. (I first tried chatgpt and the results were unusuable. Nanobana got the geometry much more right!)
• Upscaling: I used Pixelmator Pro Image editor to upscale the final renders, ensuring the textures of the Cologne Cathedral remained crisp at 4K resolution.
• Dynamic Wallpaper: To create a native macOS Dynamic Desktop, I used wallpapper CLI tool to pack these images into a single HEIC file.
  (I actually had to fork the wallpapper repository to fix a specific issue with how it handled time-interval transitions, ensuring the light shifts perfectly with the local clock.)

Previews

05:00 - City Wakes Up 06:00 - Pre-rise Pink 08:30 - Sunrise 10:00 - Bright Morning 16:00 - Soft Afternoon 18:00 - Sunset 20:00 - City Lights 22:00 - Night Lights 00:00 - Deep Night

Dynamic Wallpaper for MacOS

The following JSON schema was used to define the timings for the macOS HEIC container:

[
    {
        "fileName": "00_0000.heic",
        "time": "00:00:00"
    },

    {
        "fileName": "01_0500.heic",
        "time": "05:00:00"
    },
    {
        "fileName": "02_0700_prerise.heic",
        "time": "07:00:00"
    },
    {
        "fileName": "03_0830.heic",
        "time": "08:30:00"
    },
    {
        "fileName": "04_1000.heic",
        "isPrimary": true,
        "isForLight": true,
        "time": "10:00:00"
    },
    {
        "fileName": "05_1600.heic",
        "time": "16:00:00"
    },
    {
        "fileName": "06_1800_sunset.heic",
        "time": "18:00:00"
    },
    {
        "fileName": "07_2000.heic",
        "time": "20:00:00"
    },
    {
        "fileName": "08_2200_night.heic",
        "isForDark": true,
        "time": "22:00:00"
   }
]
		

$ wallpapper -i CologneDay.txt 
		

Dynamic Wallpaper for iOS

There is no built-in format like on macOS, BUT you can use the Shortcuts app to trigger wallpaper changes at a specific time.

How:

1. Create a Shortcut

• Open Shortcuts
• Create a new shortcut
• Add action → Find Photos
• Add action → Set Wallpaper

2. Create an Automation

• Go to Automation
• Tap ➕ → Create Personal Automation
• Choose trigger (e.g., Time of Day)
• Turn OFF “Ask Before Running”