OCR Guide — How to Extract Text from Images and Scanned PDFs

What is OCR?

OCR stands for Optical Character Recognition. It analyses an image of text and converts it into actual editable characters. Without OCR, a scanned document is just a picture you cannot edit.

How OCR works

The process: pre-processing (straighten, enhance contrast, remove noise), segmentation (divide into lines, words, characters), recognition (match character shapes to trained model), post-processing (language model corrects errors from context).

When OCR gives excellent results

Clean printed text on white background, standard fonts, high-resolution scans (300 DPI or higher), good contrast, horizontal text.

When OCR struggles

Handwritten text, low-resolution or blurry images, decorative fonts, low contrast, rotated text, complex tables, background patterns.

Tips for better results

Scan at 300 DPI minimum. Convert to black and white before running OCR. Straighten the image first. Clean up background patterns.

Working with OCR output

Always proofread against the original. Commonly confused characters: 0 and O, 1 and l and I, rn and m. Tables often come out as plain text needing reconstruction.

FAQ

Can OCR read handwriting? Neat block printing works moderately. Cursive handwriting gives poor results.

What accuracy can I expect? For clean high-quality scans: 98 to 99 percent. For lower quality images, always check the output.