How Lampka keeps figures in colour on dark pages

Why inverting breaks figures

Inverting swaps every colour for its opposite. White paper becomes black, which is what you want. But an orange bar turns blue, a blue one turns orange, and faces in photos look like film negatives. When colour carries meaning, the chart no longer matches its own legend.

What Lampka does instead

Lampka draws each page twice. The first copy is the page as printed. In the second, which you never see, it removes everything except pictures and strongly coloured shapes. That shows exactly which parts of the page belong to figures.

Everything else, the paper, the text and the lines, is recoloured from light to dark in your theme's colours, keeping the soft edges of letters smooth. The figures are left exactly as they were.

Lampka's Night theme: the text goes dark, the chart keeps its real colours.

The awkward cases

• Scanned books. A scan is one big picture of the whole page, so keeping it would leave the page bright white. A picture that fills most of the page is darkened like text instead.
• Pale shading. Light grey table rows and tinted boxes are treated like paper, so they don't glow on a dark page.
• Slides designed dark. Pages that are already light-on-dark are matched to your theme, so turning a page never dazzles you.
• Icons from icon sheets. Manuals often show one small icon cut from a large sheet. Only the part you can actually see is kept in colour.

Your PDF stays as it was

All of this happens only on your screen, on your computer. The file itself is never changed, and nothing is sent anywhere.

More about Lampka: All guides Dark mode Read aloud Papers and theses Manual