Proper image preparation significantly improves OCR accuracy. Understanding these techniques helps you get better results from any OCR service.
Resolution and Size
Higher resolution provides more detail for recognition. 300 DPI is the standard for document scanning—lower resolutions lose fine details. However, extremely large images slow processing without improving accuracy. Resize very large images to reasonable dimensions (2000-4000 pixels on the longest edge) while maintaining aspect ratio.
Contrast and Lighting
Strong contrast between text and background improves recognition. Dark text on light backgrounds works best. Uneven lighting creates shadows that can be misread. If capturing documents, use even, diffuse lighting. For post-processing, increasing contrast and converting to grayscale often helps.
Alignment and Cropping
Skewed text reduces accuracy—align images so text runs horizontally. Crop to remove borders, margins, and non-text elements. The less noise in the image, the better the results. Deskew algorithms can correct small rotations automatically, but major tilts should be fixed before OCR.
File Format Considerations
PNG preserves image quality without compression artifacts—ideal for OCR. JPEG compression can introduce artifacts around text, especially at low quality settings. For screenshots and documents, PNG is preferred. Avoid multiple re-saves in lossy formats.