#1776 True black inverted pdf color

[Speck Pratt]

"Invert colors in dark mode" maps the white page background to dark gray (45/255, or 30/255 with Increase Contrast) rather than black — the mapping is fixed in colorInvertFilters (NSGraphics_SKExtensions.m, factor f = 1.8972 / 1.9338).

Could the mapped level be made configurable, down to true black (f = 2.0)? A hidden defaults key would be fine.

Use case: reading outdoors at maximum brightness on a mini-LED/OLED display. At high nits the gray background becomes a large luminous field; a true-black background keeps emitted light to the text alone, which is also easier on photosensitive eyes. I'm running a locally patched build with f = 2.0 and the rendering holds up (text stays legible, images unaffected).

Happy to attach the diff from my local build or test a beta, if useful.

Skim 1.7.15, macOS 27.

[Speck Pratt]

Apologies — this duplicates #1774, which I missed before posting. I see from there and #1722 that the gray level is deliberate, so no need to relitigate. I'm running a locally patched build (f = 2.0) which covers my OLED/outdoor case.

[Speck Pratt]

For anyone else landing here from #1722/#1774 (or #1659/#1757): notarized builds of Skim with these available as options live at https://github.com/speckofthecosmos/skim-plus — an Advanced preferences pane with the inverted page background level (down to true black), background colors that render as picked under the invert filter, tooltip timing, and a View-menu toggle for invert. The patches only expose options: with nothing set, the builds behave exactly like stock Skim, and new upstream releases are picked up automatically.