Smart Payment Solutions
Bespoke Software Tool
Paul Huxley at Smart Payment Solutions was building up a library of product images for the till software he supplies to his customers. His existing method was to ask ChatGPT for around ten product images at a time. It would hand back a single collage with all ten products spaced out on one picture, and he would then cut each product out by hand before it could be loaded onto a till button. It worked, but it was slow, fiddly and inconsistent.
What he actually needed was the opposite of a collage: one image per product, every one built to the same fixed format, saved as its own file and named after the product. The written spec was specific — 1000×1000, product centred, plain white background, no props, filenames generated from the product name, a CSV mapping each product to its file, and the whole batch downloadable as a ZIP.
This was delivered as a fixed-scope, fixed-price software build, entirely separate from the Smart Payment Solutions website so that nothing about the tool could affect the live business site. Paul supplies his own OpenAI key and pays for image generation directly, so there is no cost sitting between him and the tool. Ownership of the underlying code is retained by lukeduff.co.uk with the client licensed to use it.
| Problem | Solution Implemented |
|---|---|
| Ten products came back as one collage that had to be cut apart by hand | Built a batch generator that calls the image API once per product, so each product returns as its own separate file ready to load straight onto a till button. Individual products can also be regenerated on their own without rerunning the whole batch. |
| Output format and file naming had to be consistent, not left to whatever the model felt like | The image instructions are assembled server-side and locked, so the user only ever supplies a product name and an optional description — never a raw prompt. Filenames are slugified from the product name automatically, and the CSV map, ZIP writer and slugger were all written from scratch rather than pulled in as third-party libraries. |
| No way to know what a batch would cost before running it | Added a live cost estimate that updates as the product list is built, plus three selectable quality tiers. The cheapest Draft tier works out at roughly a penny an image against roughly thirteen pence on High — around a fifteenfold spread, made visible in the dropdown so the choice is an informed one. |
| Paul asked whether he could import a spreadsheet instead of retyping his product list | Added CSV upload with a dependency-free parser that handles quoted fields with embedded commas, escaped quotes, mixed line endings, a UTF-8 byte order mark and an optional header row, and falls back to the simpler pipe format. Shipped a downloadable CSV template alongside it so the column order is never in question. |
| The OpenAI key is a live billing credential and must not sit on a server | The key is encrypted with AES-256-GCM and held in an httpOnly cookie in Paul’s own browser — the server never stores it. Access is gated by a passphrase check in edge middleware before any generation endpoint is reachable, and the app carries in-product guidance on setting a hard monthly spend cap on the key itself. |
| A private tool still has to survive being reachable on the public internet | Hardened in-house rather than bolting on a third-party access product: security headers, a noindex policy, constant-time passphrase comparison, and a durable rate limiter backed by object storage so it keeps counting across serverless cold starts. An independent black-box then authenticated penetration test passed 40 of 40 checks, including a critical authentication bypass that was caught and fixed during testing. |