agent failed to read faded receipt: ocr returned empty with error

TL;DR

Faded thermal receipts fall below the OCR contrast threshold, so the engine returns nothing. Preprocess the image (grayscale, contrast stretch, upscale 2x) before OCR, and route anything still empty to a human review queue instead of failing the run.

Error

agent failed to read faded receipt: ocr returned empty

Steps

1. Inspect a failing receipt image: check whether any text is visible to the human eye. Expected: faint but present text, or truly blank paper.
2. Add a preprocessing step before OCR: convert to grayscale, apply contrast stretching, and upscale to at least 300 DPI equivalent. Expected: the same image now shows stronger text edges.
3. Re-run OCR on the preprocessed image. Expected: text is extracted where the raw image returned empty.
4. For images that still return empty, push the expense to a manual-review queue with the image attached. Expected: a human reads what the OCR cannot.
5. Log the empty-OCR rate per vendor to identify systematic faded-receipt sources. Expected: a short list of vendors to handle manually by default.

When to use

• Agent OCR returns empty on faded or low-contrast receipts.
• The receipt is legible to a human but not to the OCR engine.

When not to use

• The receipt is physically crumpled or torn (see the thermal-paper skill).
• OCR returns garbage text rather than empty (see the OCR-garbage skill).

Tool compatibility

• Tesseract, cloud OCR APIs, and custom agent OCR pipelines.

Variant phrasings

OCR returned no text for receipt

Same failure, alternate wording.

Empty OCR result on faded receipt

Names the cause directly.

Why it happens

OCR engines threshold on contrast: faded thermal ink sits below the binarization cutoff, so the engine sees a blank page. Preprocessing raises the text above the threshold before recognition runs.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_yPbKs0Lqz3kolpn3Mb84Gw