This pull request introduces a change to the `Hsva` struct in the
`crates/ecolor/src/hsva.rs` file to enable serialization and
deserialization when the `serde` feature is enabled.
* Closes <https://github.com/emilk/egui/issues/7131>
* [x] I have followed the instructions in the PR template
The bug was in `Color32::from_rgba_unmultiplied` and by extension
affects:
* `Color32::from_rgba_unmultiplied`
* `hex_color!`
* `HexColor`
* `ColorImage::from_rgba_unmultiplied`
* All images with transparency (png, webp, …)
* `Color32::from_white_alpha`
The bug caused translucent colors to appear too bright.
## More
Color is hard.
When I started out egui I thought "linear space is objectively better,
for everything!" and then I've been slowly walking that back for various
reasons:
* sRGB textures not available everywhere
* gamma-space is more _perceptually_ even, so it makes sense to use for
anti-aliasing
* other applications do everything in gamma space, so that's what people
expect (this PR)
Similarly, pre-multiplied alpha _makes sense_ for blending colors. It
also enables additive colors, which is nice. But it does complicate
things. Especially when mixed with sRGB/gamma (As @karhu [points
out](https://github.com/emilk/egui/pull/5824#issuecomment-2738099254)).
## Related
* Closes https://github.com/emilk/egui/issues/5751
* Closes https://github.com/emilk/egui/issues/5771 ? (probably; hard to
tell without a repro)
* But not https://github.com/emilk/egui/issues/5810
## TODO
* [x] I broke the RGBA u8 color picker. Fix it
---------
Co-authored-by: Andreas Reich <andreas@rerun.io>
Added some DragValue widgets in the color_picker widget as input fields
for managing the RGBA values.
In case the provided values result in a not valid premultiplied alpha
RGBA color, a button will appear next to the input fields, to be used to
multiply the values with the alpha channel.

Closes <https://github.com/emilk/egui/issues/2716>.
---------
Co-authored-by: IVANMK-7 <68190772+IVANMK-7@users.noreply.github.com>
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>
Co-authored-by: Brian Janssen <tosti007@users.noreply.github.com>
* split out ecolor crate
* split up ecolor crate in lots of modules
* add changelog notes
* add readme to ecolor
* put clippy::manual_range_contains on cranky allow list
* fix hex color issues
* doc fixes
* more hex_color fixes
* Document features
* Rename hex_color module to avoid warning
* Sort the feature names
* fix link in CHANGELOG.md
* better wording
Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>