The Document Deskewer straightens tilted document scans, slanted mobile receipts, and misaligned photographic captures using precision angular canvas rotation.

### How Canvas Deskewing Works When flatbed scanners or phone camera angles tilt a page, text lines slant across the page. This tool rotates the raster image to realign text horizontally: - **Trigonometric Bounding Box Expansion**: Standard rotation can crop the corners of rotated rectangles. The deskewer calculates the expanded bounding dimensions using absolute sine and cosine offsets: $$W_{\text{new}} = W \cdot |\cos(\theta)| + H \cdot |\sin(\theta)|$$ $$H_{\text{new}} = W \cdot |\sin(\theta)| + H \cdot |\cos(\theta)|$$ - **Paper Tone Background**: Fills newly created triangular corner margins with pure white (#FFFFFF) to match standard printer paper. - **Fine Angular Slider**: Allows decimal-degree tilt adjustments so you can dial in the exact alignment angle without quality loss.

### Worked Example Straightening a document tilted 2.5 degrees clockwise: 1. Upload a crooked scan (e.g., $1200 \times 1600$ px). 2. Set the Tilt Angle slider to **2.5°** to apply a counter-clockwise correction of $-2.5^{\circ}$. 3. The canvas resizes dynamically to encompass the rotated corners and renders the straightened page against a crisp white background. 4. Download the straightened PNG ready for OCR indexing or PDF compilation.

### Local In-Browser Processing Image loading, trigonometric canvas resizing, and pixel rotation execute strictly on your local computer using the HTML5 Canvas 2D API. Sensitive tax returns, medical bills, and legal contracts are never uploaded to any remote server.