Perspective Correction (De-skewing)
Phone photos of documents are almost always taken at an angle. Good scanning apps detect the document edges and apply a perspective transform, producing a flat, rectangular image that looks like a proper scan. Without this step, the output is a photo, not a scan.
The transform is a homographic projection — four corner points on the angled photo are mapped to four corners of a rectangle matching the document's aspect ratio.
Image Enhancement for Readability
Post-capture enhancement options:
- Black and white — converts to high-contrast monochrome. Best for printed text, smallest file size.
- Grayscale — reduces color to shades of gray. Good for mixed content.
- Color — preserves original color. Best for forms with color-coded sections, photos, or stamps.
- Auto-enhance — boosts contrast and removes background noise. Works well for handwritten notes.
Lighting Tips
- Use even, diffuse lighting — avoid direct overhead light that creates shadows
- Avoid shadows across the document; use two light sources if possible
- Glossy paper reflects light; tilt the camera slightly or use a diffuser
- Natural daylight works well; avoid yellow incandescent bulbs
Multi-Page Documents
A good scanner lets you capture multiple pages in one session and combines them into a single PDF. Number your document pages before scanning so you can verify the order if you need to re-scan a page.
Scan Documents to PDF
Open ToolsVito's PDF Scanner, capture your document with your camera, apply enhancement, and download the scanned PDF — nothing uploaded to a server.