I built a tool that puts two people into one Christmas photo — then tested whether the AI keeps their faces

Every December, the same small problem shows up in my messages: couples who don't have a single good photo together. One of them travels for work, they live in different cities, or they simply never got around to taking a proper holiday picture. The photos exist — just never in the same frame.

So I built a small tool for exactly that. It's called SnapDuo. You upload one portrait of each person, pick a style, and it generates one photo of the two of you together.

How it works

Two photos in, one photo out. There are three styles right now:

• Christmas Couple — the classic: matching red sweaters in front of a Christmas tree, mugs of cocoa, holiday-card energy.
• Christmas Market — a candid-style shot at a Christmas market, Santa hats on, hot drinks in hand, crowds blurred behind you.
• Tiny Boyfriend — the meme one: she holds a miniature version of him standing in her palm.

Under the hood, generation runs on the nano-banana-2-1 model through the Kie API, at 1K resolution (about 3 credits per image). Before paying for any production generations, I validated the prompts with a free image tool first — I didn't want to burn credits discovering a prompt was broken.

The flow is deliberately boring: upload two portraits, get a watermarked preview for free, and only pay if the result actually looks like you.

The part I actually cared about: does it keep their faces?

AI couple photos have one failure mode that kills the whole product: the output looks nice, but it doesn't look like them. A pretty picture of two strangers is worthless here.

So before calling this done, I ran a stability test. Three templates, two generations each, six images total. Same input portraits every time. For each output I checked three things:

1. Faces — do both people still look like the people in the input photos?
2. Hands — the usual AI disaster zone. Any extra fingers, melted grips on the mugs, broken palms?
3. Composition — does the same template produce a comparable shot twice, or is it a slot machine?

Result: 6 out of 6 passed. Faces were recognizable in every generation, no hand or face failures in any of the six, and each template's two runs were consistent in composition and quality — similar framing, similar lighting, no wild swings. That consistency matters more to me than one lucky great shot, because users will re-roll and compare.

Each photo also gets 3 free re-rolls, because "usually consistent" is not "always," and nobody should pay to find out.

Pricing: flat pack, no credits

I went back and forth on pricing and landed on the simplest thing I could: previews are free (watermarked), and a single $9.99 pack unlocks any 3 photos in full HD without the watermark. No subscription, no expiring coins, no credit math.

The reasoning: the preview is the product demo. If the free preview doesn't look like you, you shouldn't pay — and if it does, $9.99 for three finished photos is an easy yes or no. I didn't want a pricing page that needs its own tutorial.

What went wrong (so far)

The honest flaw: background signage. In the Christmas Market shots, text on the market stall signs in the background comes out garbled — readable-looking at a glance, nonsense up close. It's blurred background detail, so it doesn't ruin the photos, but it's there and I'm not going to pretend otherwise. Faces, hands, and clothing rendered clean; distant text did not.

Privacy-wise, I kept it strict: uploaded photos are used only to generate your picture and are automatically deleted within 7 days. They're never sold or used for training.

What's next

It's Christmas season, which is either perfect timing or a deadline, depending on how you look at it. The product is live and the templates are tested. What I don't have yet is proof that strangers want this — so the real test for me is whether real users show up and unlock photos before the end of November. If they do, I'll add more scenes. If they don't, I'll have learned something cheap.

If you want to try it: SnapDuo — the preview is free. There's also a short guide on how it works, including the photo rules that make results look most like you.

I'd genuinely like feedback on two things: does the face consistency hold up with your photos, and is the flat-pack pricing clearer than the credit systems other tools use? Building this solo, so outside eyes help.