How Image Watermarking Works

Image Watermark draws your text directly onto the image's own canvas using the browser's 2D drawing API — the same technology every other image tool on PDFPilot uses to decode and re-encode photos. Nothing is overlaid as a separate layer; the watermark becomes part of the image's actual pixels, the same way it would if you'd edited it in any image editor.

Font size scales automatically with the image's dimensions — set as a percentage of the image's shorter side, rather than a fixed pixel size — so the same setting produces a legible watermark whether you upload a 400px thumbnail or a 4000px photo.

The five fixed positions (center and each corner) place one instance of your text with a margin from the edge. Tiled is different: it repeats the text diagonally across the entire image at a -30 degree angle, the same style used for proof watermarking, specifically because a single corner watermark is trivial to crop out, while a diagonal tiled pattern covers the whole frame.

Opacity is a straightforward transparency setting from 5% (barely visible) to 100% (fully solid) — lower values keep more of the underlying photo visible through the text, useful when the watermark is there to deter reuse rather than to be the focal point.

As with every tool on PDFPilot, watermarking happens entirely in your browser. Your image is never uploaded to a server.