ナレッジハブ・技術ガイド
PDFから高解像度画像への変換ツール
PDFから高解像度画像への変換ツール
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
Extraction = Decode(Binary Stream) ➔ Parse(Font Subsets) ➔ Render(Canvas Context)
To extract an image, the browser must act as a virtual printer. It reads the PDF drawing commands and mathematically paints the vectors and fonts onto an invisible HTML5 Canvas, which is then exported as a JPEG.
ベストプラクティスとガイドライン
- Set High DPI for Print: If you are converting a PDF to a JPEG for professional printing, you must render the canvas at a minimum of 300 DPI (Dots Per Inch). Rendering at standard web 72 DPI will look horribly pixelated on paper.
- Understand Text Boundaries: PDF text is not structured like a Word document; it is just characters placed at exact X/Y coordinates. Extracting text often results in weird line breaks because the PDF has no concept of 'paragraphs'.
- Beware of Scanned PDFs: If a PDF is just a scanned photo of a piece of paper, the text extractor will find zero text. It will only see a single giant image.
よくある質問 (FAQ)
Why did my extracted text lose its formatting?
PDFs do not store structural formatting (like bold, italics, or tables) in a semantic way like HTML. They only store the visual coordinates of the ink. All structural context is permanently lost upon extraction.
Can I convert the JPEG back into a perfectly editable PDF?
No. Converting a PDF to a JPEG 'flattens' or 'rasterizes' the document. The text is no longer math; it is just pixels. You cannot un-bake the cake.
Is it safe to convert bank statements here?
Absolutely. The PDF.js engine runs locally. The document never leaves your machine, ensuring total data privacy for sensitive financial extraction.