Improve serializing

[Ogeon]

This fixes a long-standing bug in how Alpha and PreAlpha are serialized. They used to be flattened to a map, which is fine in JSON but not in more expressive formats, such as RON. The replacement implementation will only handle a subset of possible values (structs, tuples and sequences), but they should be the most common ones. It should also be possible to extend it later.

I have also taken the opportunity to add some helpful utility functions for serializing and de-serializing.

Closed Issues

• Fixes Serialization not compatible with many formats because of flatten #130, using a custom implementation.

Breaking Change

Technically breaking, since it changes the serialization format a bit, but the old behavior was buggy and not always usable. The serialized type and name for Alpha and PreAlpha is now inherited from the color's type. So, for example, Srgba will be serialized and de-serialized as an Rgb struct with an additional alpha field. Unit types get extended to newtypes, and newtypes get extended to tuples.

[Ogeon]

bors r+

[github-actions]

Benchmark for ecd70f8

Click to view benchmark

Test	Base	PR	%
Cie family/lab to lch	3.0±0.02µs	3.1±0.02µs	+3.33%
Cie family/lab to xyz	764.1±3.96ns	764.3±3.40ns	+0.03%
Cie family/lch to lab	2.4±0.01µs	2.4±0.02µs	0.00%
Cie family/linsrgb to xyz	285.2±1.48ns	291.8±2.50ns	+2.31%
Cie family/linsrgb to xyz - wide::f32x8	103.5±0.45ns	103.3±0.54ns	-0.19%
Cie family/xyz to lab	21.1±0.18µs	21.2±0.73µs	+0.47%
Cie family/xyz to yxy	662.1±2.92ns	655.5±3.39ns	-1.00%
Cie family/yxy to xyz	525.5±1.63ns	534.2±5.89ns	+1.66%
Matrix functions/matrix_inverse	11.5±0.11ns	11.7±0.05ns	+1.74%
Matrix functions/multiply_3x3	10.5±0.05ns	10.4±0.04ns	-0.95%
Matrix functions/multiply_rgb_to_xyz	6.4±0.05ns	6.4±0.10ns	0.00%
Matrix functions/multiply_xyz	6.4±0.01ns	6.4±0.03ns	0.00%
Matrix functions/multiply_xyz_to_rgb	6.4±0.04ns	6.4±0.03ns	0.00%
Matrix functions/rgb_to_xyz_matrix	30.1±0.13ns	30.1±0.12ns	0.00%
Rgb family/hsl to hsv	643.5±6.26ns	640.4±6.32ns	-0.48%
Rgb family/hsl to linear hsl	12.1±0.06µs	12.3±0.10µs	+1.65%
Rgb family/hsl to rgb	1989.9±8.40ns	1991.0±9.66ns	+0.06%
Rgb family/hsv to hsl	848.9±12.77ns	817.9±11.04ns	-3.65%
Rgb family/hsv to hwb	223.0±0.83ns	222.7±0.97ns	-0.13%
Rgb family/hsv to linear hsv	10.7±0.04µs	11.3±0.05µs	+5.61%
Rgb family/hsv to rgb	1853.0±10.65ns	1917.4±19.35ns	+3.48%
Rgb family/hwb to hsv	464.5±3.81ns	498.3±6.42ns	+7.28%
Rgb family/hwb to linear hwb	11.3±0.05µs	11.9±0.06µs	+5.31%
Rgb family/linear hsl to hsl	10.7±0.05µs	10.7±0.07µs	0.00%
Rgb family/linear hsv to hsv	10.1±0.05µs	10.2±0.05µs	+0.99%
Rgb family/linear hwb to hwb	10.8±0.08µs	11.0±0.08µs	+1.85%
Rgb family/linsrgb to rgb	5.5±0.03µs	5.5±0.12µs	0.00%
Rgb family/linsrgb to rgb - wide::f32x8	5.4±0.03µs	5.4±0.03µs	0.00%
Rgb family/linsrgb_f32 to rgb_u8	906.2±3.75ns	908.0±3.48ns	+0.20%
Rgb family/linsrgb_f64 to rgb_u8	1170.3±4.99ns	1169.3±5.12ns	-0.09%
Rgb family/rgb to hsl	801.0±7.21ns	801.0±4.80ns	0.00%
Rgb family/rgb to hsl - wide::f32x8	497.5±2.23ns	497.8±2.18ns	+0.06%
Rgb family/rgb to hsv	498.1±1.89ns	498.4±2.18ns	+0.06%
Rgb family/rgb to hsv - wide::f32x8	439.6±1.82ns	435.4±1.78ns	-0.96%
Rgb family/rgb to linsrgb	7.5±0.09µs	8.0±0.04µs	+6.67%
Rgb family/rgb to linsrgb - wide::f32x8	3.7±0.02µs	3.7±0.01µs	0.00%
Rgb family/rgb_u8 to linsrgb_f32	331.8±1.43ns	332.5±1.45ns	+0.21%
Rgb family/rgb_u8 to linsrgb_f64	331.5±1.09ns	331.5±1.58ns	0.00%
Rgb family/xyz to linsrgb	337.7±1.36ns	339.8±1.35ns	+0.62%
Rgb family/xyz to linsrgb - wide::f32x8	103.8±0.41ns	102.8±0.68ns	-0.96%

[bors]

Build succeeded:

• ci