With Watermark on, the Export dialog shows the first photo it will export
(its cached thumbnail) with the watermark drawn as the file will have it.
The watermark is redrawn on a copy only when it or the output size changes.
draw_watermark_preview scales the 6 px minimum text size and the 1 px
minimum shadow offset by the preview size over the export size, so a small
watermark doesn't look bigger in the preview than in the file. Exports draw
with a scale of 1 and are unchanged.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
