Two layers to stop tesseract hallucinating text on phone photos:
1. Bradley adaptive threshold (O(N) via integral images) turns the
downscaled grayscale image into a binary B/W mask. Cuts out
gradients, shadows, and surface texture that tesseract
misreads as ink.
2. After recognise(), filter data.words by confidence >= 60 and
re-assemble lines from kept words. Status line surfaces how
many were dropped so the cost is visible.
Output of preprocess stage is PNG (not JPEG) so the sharp B/W
edges don't get re-blurred.
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