I built a Windows tool that turns screenshots into one searchable PDF — here's what I learned

For months I had the same annoying problem: folders full of screenshots I couldn't actually use. Lecture slides, PDFs I own, scanned pages — all just images . I couldn't Ctrl-F them, couldn't copy a line out, couldn't get my OS to index them. A picture of text is useless the moment you need to find something in it. So I built CapDrop to automate the whole chain on Windows. This is a write-up of how it works under the hood and the bugs that nearly broke me. The core idea You draw a capture box over a page, pick a page key (Page Down, arrow keys), set an interval, and walk away. CapDrop then: Captures each page on the interval Presses the page key for you to advance Auto-crops margins and toolbars out of every shot Runs OCR locally Binds everything into a single PDF with a real text layer The result is one document you can search, not a pile of images. The stack Electron for the app shell and capture/UI (I already had window management, hotkeys, and floating-bubble export working — no reason to rewrite). A Python OCR sidecar (RapidOCR) spawned as a child process. OCR runs 100% locally; nothing is ever uploaded. jimp for auto-crop, with a 12px safety pad so edge text never gets clipped. pdf-lib to bind the pages and inject the OCR text layer. The Electron + Python-sidecar split was a deliberate choice. People kept telling me to rewrite the whole thing in Python "for the OCR," but the Electron app already had everything except OCR. Adding a sidecar was a few hundred lines; a rewrite would've been months. The bug that cost me two days After adding the OCR pipeline, my global capture hotkey developed a 4-second delay on the first press. Cold, every time. I guessed wrong twice — thumbnail size, then a race condition. Both were dead ends. The only thing that actually found it was instrumenting the hot path with timing logs. The culprit: a fs.readFile of a tiny 749-byte settings.json on every hotkey press. On a cold start that read was taking 2–4 seconds — Windows Defender's