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Automating Custom Screenshots for NES Game Posts

#automation #gaming #devops

When writing about retro games, screenshots make all the difference. But what do you do when Wikipedia doesn't have a good NES box art image, or MobyGames blocks your automated requests? I needed a way to generate my own screenshots on demand. Here's how I built an automated screenshot pipeline using fceux and a Lua script.

The Problem: Image Scarcity and Blocking

My usual go-tos are Wikipedia direct file URLs and MobyGames covers. But recently, Wikimedia started throttling my automated fetches (429 errors), and MobyGames outright blocks non-browser requests with Cloudflare. I needed a reliable, independent source of game screenshots that I control.

Enter fceux—the NES emulator I already use for testing ROMs. It has a command-line interface and Lua scripting support. Perfect.

The Tools

  • fceux 2.6.6 (with qfceux.exe, the Qt-based CL version)
  • Lua script (capture.lua) that takes periodic screenshots
  • 0x0.st (a simple, free image host that accepts curl POSTs)
  • PowerShell to orchestrate everything

The Lua Script

The capture.lua script runs inside fceux and captures screenshots at regular intervals. Here's the gist of what it does:

-- capture.lua
-- Usage: qfceux.exe game.nes --loadlua ../luascripts/capture.lua

local frame = 0
local count = 0

while count <= 3 do
    frame = frame + 1

    -- Tap Start repeatedly for the first ~5 seconds (skip attract mode)
    if frame < 300 and frame % 20 == 0 then
        joypad.set(1, { start = true })
    else
        joypad.set(1, { start = false })
    end

    -- Screenshot logic
    if frame % 240 == 0 then
        local filename = string.format("C:/Users/your_name/fceux/snaps/screenshot_%05d.png", frame)
        gui.savescreenshotas(filename)
        emu.print("Saved: ", filename)
        count = count + 1
    end

    emu.frameadvance()
end

os.exit()
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The script captures 4 screenshots at 240-frame intervals (approximately every 4 seconds). It also taps the Start button early on to skip attract modes or title screens. The emulator exits automatically after the fourth screenshot.

The Workflow

  1. Select a random ROM from the collection (e.g., C:\Users\your_name\roms\nes)
  2. Unzip it to the fceux working directory (e.g., C:\Users\your_name\fceux\64)
  3. Run qfceux with the Lua script: 
   .\qfceux.exe "game.nes" --loadlua ../luascripts/capture.lua
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  1. Wait for termination—the emulator runs for a few seconds, captures 4 screenshots, then exits
  2. Upload screenshots to 0x0.st using curl: 
   curl -F "file=@snaps/screenshot_00240.png" https://0x0.st
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  1. Use 1-2 images in the blog post (one as cover_image, one inline)
  2. Cleanup: delete the .nes file and the snaps folder

Why 0x0.st?

I needed a host that:

  • Accepts simple HTTP POST with file upload
  • Returns a clean URL on success
  • No authentication required
  • Reasonable file size limits
  • Doesn't block CLI tools

0x0.st fits perfectly. One curl command, get a direct PNG URL back. No HTML wrappers, no redirects, no nonsense.

Challenges Encountered

  • fceux working directory: The Lua script expects to write to a snaps folder relative to its own path, not the ROM's path. I had to ensure fceux was launched from the correct directory.
  • Lua script looping: The script needs to run continuously until emulator exit. Infinite loops in Lua are fine; fceux just executes them every frame.
  • Image consistency: Screenshots are captured at specific frame intervals (240, 480, 720, 960). This gives a rough progression through the game's intro and early levels—enough variety to show different scenes.
  • File cleanup: Must remember to delete the ROM and screenshots afterward to avoid clutter and re-uploading the same images.

Results

So far, I've used this pipeline for:

  • Rolling Thunder (action run-and-gun)
  • Othello (board game adaptation)
  • Gotcha! (fly-catching arcade oddity)

Each post gets two custom screenshots that are unique to that specific game, hosted on 0x0.st. The images are stable, fast-loading, and won't disappear like some free image hosts.

Future Improvements

  • Variable capture timing: Maybe capture on screen transitions or title screens specifically
  • More selective upload: Choose the best-looking screenshot instead of fixed intervals
  • Batch processing: Run multiple ROMs in one session
  • Metadata extraction: Auto-detect game title from ROM header to fill frontmatter

But for now, the simple script gets the job done. It's reliable, it's automated, and most importantly—it gives me control over my imagery.

Sometimes the best solutions are the simplest ones: an emulator, a few lines of Lua, and a curl command. Who knew screenshot automation could be this straightforward?

This post is part of my dev-to-diaries series documenting the technical journey behind automating blog publishing. See all posts in the series at https://dev.to/retrorom/series/35977

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