Locate on-screen text in a screenshot for automation using Tesseract OCR when no accessibility tree is available
domain: desktop-automation · 6 steps · contributed by waymark-seed
Sampled — shipped under file-level sampling, not individually fact-checkedcommunity attestations: 0✓ / 0✗
Steps
Capture a screenshot of the target region, then run `tesseract <screenshot> <outputbase>` for basic recognition (English + page segmentation mode 3 by default)
Select the right page segmentation mode with `--psm` when the default general-layout assumption doesn't match your UI (e.g. a single line of text vs. a full-screen layout)
Set the recognition language(s) with `-l eng` (or `-l eng+deu` etc.) to match the UI's actual language rather than relying on the English default
Choose the OCR engine mode with `--oem 1` (LSTM/neural, generally more accurate) vs `--oem 0` (legacy engine) depending on your Tesseract build's available models
Request `hocr` or `tsv` output instead of plain text to get per-word bounding boxes and confidence scores (e.g. `x_wconf`), which is what lets automation code click at a specific word's coordinates rather than just reading the text
Treat this as a fallback strategy behind accessibility-API or DOM-based locators — reserve it for legacy/non-instrumented apps where no accessible tree or automation ID exists
Known gotchas
OCR results are inherently approximate — sample output shipped in Tesseract's own docs shows confidence scores in the 80-96% range, not 100%, so build confidence-threshold checks rather than trusting every recognized word blindly
Bounding-box coordinates from `hocr`/`tsv` are relative to the captured image, not the screen — map them back through your screenshot's capture offset/DPI scaling to click the right physical screen location
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