Add NAP-5: proposal for an updated napari logo (napari#5084)

* Add NAP-5 new logo proposal

* Text updates to NAP5

* Update logo to have a small (8%) margin

* Fix header reference in NAP-5

* Add NAP5 to TOC

* Add comparison image

* Add missing comparison file for NAP5

* Fix typo in relative image url

docs/_toc.yml

@@ -107,6 +107,7 @@ subtrees:
               - file: naps/2-conda-based-packaging
               - file: naps/3-spaces
               - file: naps/4-async-slicing
+              - file: naps/5-new-logo
           - file: developers/documentation/index
             subtrees:
             - entries:

docs/naps/5-new-logo.md

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+(nap-5-new-logo)=
+
+# NAP-5 — New logo (2022)
+
+```{eval-rst}
+:Author: Juan Nunez-Iglesias <[email protected]>
+:Created: 2022-09-08
+:Resolution: <url> (required for Accepted | Rejected | Withdrawn)
+:Resolved: <date resolved, in yyyy-mm-dd format>
+:Status: Draft
+:Type: Standards Track
+:Version effective: 0.5
+```
+
+## Abstract
+
+This NAP proposes a new, mathematically-defined logo for napari.
+
+## Motivation and Scope
+
+The original napari logo was simply a square crop of [this
+image](https://en.wikipedia.org/wiki/Napari#/media/File:Tabuaeran_Kiribati.jpg)
+of Tabuaeran, the island containing the village of Napari — the namesake of
+this project:
+
+![Satellite image of Tabuaeran](https://upload.wikimedia.org/wikipedia/commons/d/dc/Tabuaeran_Kiribati.jpg)
+
+A few months later, Jeremy Freeman, then director of Computational Biology at
+CZI, and a bit of a design nerd, traced the island and gave us our current,
+stylised version of that image.
+
+![napari-logo-2](../images/logo.png)
+
+Being, the shape is very irregular — no one knows what it is — and the
+gradients, the border around the logo, and the slightly rounded corners on a
+very square shape all look dated in 2022.
+
+This NAP deals specifically with the *shape* of the logo. It proposes specific
+colors for each logo element but is not strongly opinionated on them — they can
+be decided in the implementation phase, and perhaps in subsequent NAPs.
+
+## Detailed Description
+
+This proposal keeps the original inspiration of the Tabuaeran atoll, which is
+quite beautiful and has the added bonus of looking a bit like a dividing cell.
+However, it goes much further in the styling.
+
+The proposed logo draws the two "lobes" of the island as two touching circles,
+with the radius of the smaller (northwest) circle being a factor of $\phi$
+smaller than the larger one, where $\phi = \frac{1 + \sqrt{5}}{2}$ denotes the
+[golden ratio](https://en.wikipedia.org/wiki/Golden_ratio).
+
+The "neck" of the island is *also* defined by two *external* circles: one
+smaller again by $\phi$ than the smaller circle, and one larger again than the
+bigger circle. In this way, the island is defined by four circles of increasing
+radius, with each increase a factor of $\phi$:
+
+![napari-logo-3-with-guides](../images/napari-logo-3-with-guides.png)
+
+Additionally, the background of the logo is a
+[squircle](https://www.johndcook.com/blog/2018/02/13/squircle-curvature/) of
+degree 5, as Apple [uses](https://stackoverflow.com/a/47342594/224254) for iOS
+and macOS icons currently.
+
+Overall, the new icon still keeps the "napari" character, while looking more
+modern, friendlier, and more abstract. This is an advantage for those who don't
+know the origin of the logo, as they would still be able to appreciate the
+regularity of the shapes used.
+
+Additionally, the logo looks quite a bit like a dividing budding yeast *(S.
+cerevisiae)*, rather than an amorphous anonymous cell, which anyone with a
+background in biology would appreciate!
+
+Here is the proposed logo together with the old one:
+
+![napari-logo-comparison](../images/napari-logo-old-new.png)
+
+The new logo at 100% scale:
+
+![napari-logo-3](../images/napari-logo-3.png)
+
+## Related Work
+
+N/A
+
+## Implementation
+
+This is the fun bit. 😃
+
+The logo proposed above is generated *entirely within napari*. It makes use of:
+
+- A Shapes layer for each element: the background, the sand, the rainforest,
+  and the lagoon.
+- Scaling, translation, and rotation on each layer: the arithmetic for finding
+  the exact centers and contact points of all the circles is much easier with
+  the origin at the center of the north-west circle, a radius of
+  $1/\phi = \phi - 1$, and the island aligned along the 0th (vertical) axis.
+  Similarly, the squircle is easier to draw with the origin at the center. I
+  then apply scale, translation and rotation so that the island is at 45° and
+  the logo fills the space in [[0, 1024], [0, 1024]].
+- NumPy for computation of all the lines and shapes.
+
+Additionally, napari was used extensively during the development, to debug
+errors in calculating the contact points and so on. 😅
+
+It's very fun to work with powers of $\phi$: $1/\phi = \phi - 1$, which implies
+$1/\phi^2 = (\phi - 1)/\phi = 1 - 1/\phi = 2 - \phi$, and so on. Similarly,
+$\phi^2 = 1 + \phi$, which again lets you reduce all polynomials of $\phi$ to
+degree 1.
+
+The original implementation is at https://github.com/jni/new-napari-logo, but
+if this NAP is accepted, it would add the logo-generating script as a gallery
+example.
+
+Another bit of mathematical fun: Veritasium calls $\phi$ "the fiveiest number"
+(in [this fantastic video](https://youtu.be/48sCx-wBs34)): it is the ratio of
+the diagonal of a regular pentagon to its side, and it can be written as
+$\phi = 0.5 + 0.5 \times 5^{0.5}$! So it is a happy not-quite-coincidence that
+this is NAP-5. 😉
+
+## Backward Compatibility
+
+This NAP does not raise backwards compatibility concerns.
+
+## Future Work
+
+As mentioned above, this NAP is about the shapes of the logo, not the colors.
+The colors are sampled from Wikipedia's satellite image of Tabuaeran, except for
+the lagoon, which is the turquoise of the napari-hub and napari sphinx theme.
+It's kinda nice to have those match, but not necessary. We *could* change the
+color to be more natural (again sampled from the satellite) *and* update our
+themes to match. Or we could simply pick a more natural color for the lagoon,
+again from the satellite image, and forget about matching them.
+
+I will take the opportunity to express two strong opinions:
+- I think some form of "ocean purple" is absolutely necessary for the
+  background, as I think it's become part of our identity on account of our
+  existing logo.
+- Whatever exact colors we pick, I think they should continue to evoke the
+  island: ocean, sand, forest, lagoon. There's a lot of range in that space but
+  I think we should keep to that constraint.
+
+If anyone is keen to experiment with different colors I would be glad to pass
+the design baton over.
+
+Other design questions:
+
+- Do we want a slight drop shadow? It is quite standard in macOS icons, and
+  one looks quite sparse without it.
+- Do we want a sunlight reflection/sheen on the ocean part? I'm open to it.
+- For either of those, ideally, we would keep the image processing in Python
+  and napari.
+
+## Alternatives
+
+We could of course go for a more traditionally developed logo. However, I think
+the mathematical story and the ability to generate the logo *using* napari are
+actually important. So I'd love to keep at least a large part of the concept
+for the logo, regardless of where this NAP lands.
+
+It's been suggested that the squircle shape might make it harder to tile a
+laptop together with other stickers, or align the edges. However, I think the
+tiling issue is a red herring because a quick look at the [NumFOCUS sticker
+table](https://twitter.com/NumFOCUS/status/1547651122654916609) shows that most
+related projects have irregularly-shaped stickers anyway. Additionally, I think
+that the squircle provides both a long enough straight edge (almost 1/3 of each
+side is exactly straight) to align things, but the smooth curvature makes
+slight misalignments perceptually harder to notice than a perfect straight edge.
+
+At any rate, we can provide a variety of background shapes for different
+contexts anyway. I think the squircle shape is indeed more visually appealing
+than a square with rounded corners thanks to its "curvature continuity." If we
+prefer a straighter edge, we can easily increase the degree of the squircle.
+
+## Discussion
+
+This section will be updated with links as we discuss the NAP.
+
+## References and Footnotes
+
+## Copyright
+
+This document is dedicated to the public domain with the Creative Commons CC0
+license [^id3]. Attribution to this source is encouraged where appropriate, as per
+CC0+BY [^id4].
+
+[^id3]: CC0 1.0 Universal (CC0 1.0) Public Domain Dedication,
+    <https://creativecommons.org/publicdomain/zero/1.0/>
+
+[^id4]: <https://dancohen.org/2013/11/26/cc0-by/>