style/color: derive serialize & deserialize

Using serde is useful in production, not just during development,
so move it to normal dependencies instead of dev-dependencies.

This allows to derive serialize/deserialize for the color structs
which are very simple using the default implementation, allowing
to pass colors along via serialization channels and formats.

plotters/Cargo.toml

@@ -20,6 +20,7 @@ deprecated = { level = "allow" }
 [dependencies]
 num-traits = "0.2.14"
 chrono = { version = "0.4.32", optional = true }
+serde = "1.0.139"
 
 [dependencies.plotters-backend]
 version = "0.3.6"
@@ -122,7 +123,6 @@ itertools = "0.10.0"
 criterion = "0.5.1"
 rayon = "1.5.1"
 serde_json = "1.0.82"
-serde = "1.0.139"
 serde_derive = "1.0.140"
 
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]

plotters/src/style/color.rs

@@ -3,6 +3,8 @@ use super::ShapeStyle;
 
 use plotters_backend::{BackendColor, BackendStyle};
 
+use serde::{Deserialize, Serialize};
+
 use std::marker::PhantomData;
 
 /// Any color representation
@@ -63,7 +65,7 @@ impl<T: Color> Color for &'_ T {
 /// of color
 ///
 /// If you want to directly create a RGB color with transparency use [RGBColor::mix]
-#[derive(Copy, Clone, PartialEq, Debug, Default)]
+#[derive(Copy, Clone, PartialEq, Debug, Default, Serialize, Deserialize)]
 pub struct RGBAColor(pub u8, pub u8, pub u8, pub f64);
 
 impl Color for RGBAColor {
@@ -83,7 +85,7 @@ impl From<RGBColor> for RGBAColor {
 }
 
 /// A color in the given palette
-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default, Serialize, Deserialize)]
 pub struct PaletteColor<P: Palette>(usize, PhantomData<P>);
 
 impl<P: Palette> PaletteColor<P> {
@@ -104,7 +106,7 @@ impl<P: Palette> Color for PaletteColor<P> {
 }
 
 /// The color described by its RGB value
-#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default)]
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug, Default, Serialize, Deserialize)]
 pub struct RGBColor(pub u8, pub u8, pub u8);
 
 impl BackendStyle for RGBAColor {
@@ -129,7 +131,7 @@ impl BackendStyle for RGBColor {
 }
 
 /// The color described by HSL color space
-#[derive(Copy, Clone, PartialEq, Debug, Default)]
+#[derive(Copy, Clone, PartialEq, Debug, Default, Serialize, Deserialize)]
 pub struct HSLColor(pub f64, pub f64, pub f64);
 
 impl Color for HSLColor {