ナレッジハブ・技術ガイド
PDF・画像回転ツール（90度・180度・270度）
PDF・画像回転ツール（90度・180度・270度）
本ツールは100%クライアントサイド（ブラウザ内）で動作します。写真、動画、音声、PDFファイルが外部サーバーにアップロードされることは一切なく、お使いの端末のメモリ内で安全に処理されます。
コアアーキテクチャ & 計算式
Affine Transform = [cos(θ), sin(θ), -sin(θ), cos(θ), tx, ty]
Where θ is the rotation angle in radians, and tx/ty are the translation offsets required to keep the rotated content within the visible canvas bounds. For 90° and 270° rotations, the output dimensions (width and height) are swapped.
ベストプラクティスとガイドライン
- Understand Lossless PDF Rotation: PDF page rotation modifies only the page's /Rotate dictionary entry. The actual content streams (text, vectors, embedded images) are not re-encoded, making this a metadata-only, zero-quality-loss operation.
- Swap Dimensions for 90°/270°: When rotating an image by 90° or 270°, the output canvas must swap its width and height dimensions. A 1920×1080 landscape photo becomes a 1080×1920 portrait image after a 90° rotation.
- Check Scanner Settings First: If you frequently receive sideways scans, configure your scanner's auto-orientation detection (available on most modern scanners) rather than correcting every document after the fact.
よくある質問 (FAQ)
Does rotating a PDF reduce its quality or increase file size?
No. PDF rotation is a lossless metadata operation. The tool modifies the page's rotation property in the PDF dictionary without touching the actual content streams, so file size and quality remain identical.
Can I rotate individual pages of a multi-page PDF?
The current tool rotates all pages by the same angle. For per-page rotation, use the PDF Splitter to extract the target page, rotate it individually, then merge it back into the original document.
What image formats are supported for rotation?
Any format your browser can render: JPEG, PNG, WebP, GIF, BMP, AVIF, and SVG raster. The output is always PNG to preserve maximum quality and transparency.