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OCR basics

OCR turns a picture of a page into text a computer can search, copy and export. These posts explain the ideas and vocabulary behind it in plain terms, so the rest of the blog makes sense. Start with PDF text recognition, which covers what OCR is and what it gives you, then use the glossary to look up any term.

  1. Scanned PDF Metadata: What the File Says About Itself

    Scanned PDF metadata explained: the dates, title, author and producer fields a scan carries, where a PDF stores them, and what they can and cannot tell you.

    metadatascanned pdfdocument properties

  2. What Is Optical Mark Recognition? Checkboxes and OMR

    What optical mark recognition is, how OMR decides a checkbox or bubble is filled, how it differs from reading text, and what to verify on a legal form.

    omrcheckboxesforms

  3. OCR Text Recognition Online: What Happens After Upload

    OCR text recognition online means a web page reads your scan. See what happens after upload, where the reading runs, and what limits and free tiers mean.

    online ocrocr basicsuploads

  4. Does OCR Use a Dictionary? Why Names Get Corrected

    Does OCR use a dictionary? Many engines do, and it is one reason a surname or legal term comes back as a common word. See how it works and what to test.

    dictionarylanguage modelocr errors

  5. What Is PDF/A? The Archival PDF and What OCR Adds to It

    PDF/A is the ISO standard for PDF files meant to be kept for years. What it forbids, what the version labels mean, and how a scan with OCR text fits.

    pdf/aarchivingcourt filing

  6. How Is OCR Accuracy Measured? Character and Word Rates

    How OCR accuracy is measured: character and word error rates, the checked transcript behind every figure, and how to measure a sample of your own pages.

    ocr accuracyerror rateground truth

  7. ICR vs OCR: Handprint Recognition Explained

    ICR vs OCR in plain terms: OCR reads machine print, ICR reads characters printed by hand in form fields. What each label covers and what to test.

    icrhandprintocr basics

  8. What Is Zonal OCR? Reading Set Areas of a Form

    Zonal OCR reads only the marked areas of a page, using a template drawn for one form layout. See how it works, which legal forms suit it and where it fails.

    zonal ocrformstemplates

  9. Table OCR: How Software Reads Rows, Columns and Cells

    Table OCR reads a scanned table as rows, columns and cells, not loose text. Learn the vocabulary, why merged cells fail, and how a table is stored.

    tablesocr basicsstructured data

  10. How to Make PDF Readable to Search, Software and People

    How to make a PDF readable depends on who reads it: search needs a text layer, software needs structure, a screen reader needs tags. Fixes and tests for each.

    readable pdfmachine-readableaccessibility

  11. Searchable PDF: What the File Holds and How to Spot One

    A searchable PDF pairs each page with real characters a reader can find. What the file holds, the two ways it is built, and what the label does not promise.

    searchable pdftext layerocr basics

  12. OCR Glossary for Lawyers: Terms Vendors and Courts Use

    An OCR glossary for legal work: recognition, file, scanning, quality, layout and production terms, each defined in a line with a link to the full post.

    glossaryocr basicsdefinitions

  13. Grayscale vs Black and White Scanning for OCR

    Grayscale vs black and white scanning for OCR: what each mode records, what black and white throws away, how file size changes, and a table to choose by.

    color modegrayscalescanner settings

  14. PDF Text Recognition: What OCR Is and What It Gives You

    PDF text recognition is OCR: software reads the picture of a scanned page and records the characters. What goes in, what comes out, and how far to trust it.

    ocr basicstext recognitionscanned pdf

  15. Best Font for OCR: Typefaces That Scan and Read Cleanly

    The best font for OCR depends on letter shapes, not a brand name. See OCR-A and OCR-B, the typeface features that cause misreads, and a test for your own pages.

    fontstypefacesocr basics

  16. Scan a PDF for Text: How Search Inside a PDF Works

    To scan a PDF for text, your reader matches what you type against characters stored in the file. How that works, the options, and why searches come up empty.

    pdf searchtext layerocr basics

  17. OCR Extract Text From PDF: What Happens Inside

    What happens when OCR tools extract text from a PDF: six stages from upload to output, how each stage fails, and how the failure shows on a legal page.

    text extractionocr basicspdf

  18. Convert PDF to Non Searchable PDF: Flattening Explained

    To convert a PDF to a non searchable PDF, turn each page into an image and rebuild the file. Methods, a test for leftover text, and what the reader loses.

    flatteningimage-only pdfredaction

  19. OCR Text Scanner: Does the Scanner or Software Read It?

    An OCR text scanner photographs the page; software does the reading. Where that software runs, what a copier's searchable PDF button does, and what to pick.

    scannerscopier ocrocr basics

  20. Lossy vs Lossless Compression in a Scanned PDF

    Lossy vs lossless compression in a scanned PDF: what Group 4, JPEG, JBIG2 and Flate each do, how a digit can change, and which to accept for a record copy.

    compressionscanned pdfjbig2

  21. Document OCR: How Software Maps a Page Before Reading It

    Document OCR maps a page into regions before it reads any letters. See how layout analysis works, what word coordinates record, and how to test software.

    layout analysisbounding boxesocr basics

  22. Best DPI for OCR: What Resolution Means on a Scanned Page

    The best DPI for OCR is 300 for ordinary type and 400 to 600 for small print. See what the number means in pixels per letter and when it stops helping.

    dpiscan resolutionscanner settings

  23. What Is Duplex Scanning? Both Sides of a Page in One Pass

    What duplex scanning is, how single-pass and manual two-sided scans differ, how back sides get lost, and how to tell from the page order what was captured.

    duplex scanningscanner settingspage order

  24. OCR Hallucination: When Software Adds Words to a Page

    An OCR hallucination is fluent text in the output that the page never contained. Learn why it happens, which pages invite it, and how to catch it in a file.

    hallucinationai ocrproofreading

  25. What Is Intelligent Document Processing? IDP vs Plain OCR

    What is intelligent document processing? IDP adds classifying, extracting and validating on top of OCR. See the stages and what to ask a vendor.

    idpocr basicsclassificationextraction

  26. What Is an OCR Engine? The Part Inside Every OCR Tool

    An OCR engine is the component that turns a page image into characters. How it differs from the OCR program you use, and when a law firm should ask about it.

    ocr engineocr basicsvendor questions

  27. What Is an OCR File? The Forms Recognized Text Takes

    What is an OCR file? Any file holding text recognized from a page image: a searchable PDF, a text file, Word or data. How to tell if you have one.

    ocr basicsfile formatssearchable pdf

  28. OCR vs Manual Data Entry: Retype the Page or Read It?

    OCR vs manual data entry for legal documents: how a typist's errors differ from a machine's, checks such as double keying, and a timing test for your own file.

    data entryocr errorsproofreading

  29. Native PDF vs Scanned PDF: Why the Difference Matters

    Native PDF vs scanned PDF: one stores the characters that were typed, the other stores a photograph of paper. How to tell them apart and why to ask for native.

    native pdfscanned pdfocr basics

  30. OCR Confidence Score: What the Number Does and Does Not Say

    An OCR confidence score is the software's own estimate that it read text correctly. Learn how the score is made, where it misleads and how to use it.

    confidence scoreocr reviewproofreading

  31. How Does OCR Work? From Page Image to Characters

    How does OCR work? Follow a scanned page from pixels to lines, words and letters, see how each shape is classified, and trace an error to its stage.

    ocr basicssegmentationcharacter recognition

  32. OCR Preprocessing: What Software Does to a Scan First

    OCR preprocessing is the image cleanup software runs before it reads a scan. Learn what binarization and despeckling do, and what they can erase.

    ocr basicsbinarizationimage cleanup

  33. Hidden Text in a PDF: What Sits Under a Redaction Box

    Hidden text in a PDF is text the file stores but the page does not show. Why a drawn black box leaves words readable, how to find them and remove them.

    redactionhidden textmetadata

  34. Flatbed vs Sheet Fed Scanner for Legal Files and OCR

    Flatbed vs sheet fed scanner for legal papers: which originals stay off the feeder, the faults each device adds to a scan, and what that means for OCR.

    scannersdocument feederflatbedscan quality

  35. OCR for PDF Documents: Which Files Need It, Which Do Not

    OCR for PDF documents is needed only where pages are pictures. How to sort scans, typed files and mixed files, and when running OCR again does harm.

    ocr basicsscanned pdftext layer

  36. What Is a TIFF File? The Scanner Format Lawyers Still Get

    What a TIFF file is: single-page and multi-page layouts, the tags that record resolution and software, why it holds no text, and why some viewers fail.

    tifffile formatsscanned images