feat: color hex string support alpha channel

src/color/stringify.rs

@@ -1,7 +1,14 @@
 use crate::{
     conversion::{
-        cmyk::rgb2cmyk, hex::rgb2hex, hsl::rgb2hsl, hsv::rgb2hsv, hwb::rgb2hwb, lab::rgb2lab,
-        xyz::rgb2xyz, ycbcr::rgb2ycbcr, yuv::rgb2yuv,
+        cmyk::rgb2cmyk,
+        hex::{rgb2hex, rgba2hex},
+        hsl::rgb2hsl,
+        hsv::rgb2hsv,
+        hwb::rgb2hwb,
+        lab::rgb2lab,
+        xyz::rgb2xyz,
+        ycbcr::rgb2ycbcr,
+        yuv::rgb2yuv,
     },
     helper::round,
     Color,
@@ -17,8 +24,16 @@ impl Color {
     ///
     /// let color = Color::new(255.0, 255.0, 255.0, 1.0);
     /// assert_eq!(color.hex(), "#ffffff");
+    ///
+    /// let color = Color::new(255.0, 255.0, 255.0, 0.5);
+    /// assert_eq!(color.hex(), "#ffffff80");
     /// ```
     pub fn hex(self) -> String {
+        if self.alpha != 1.0 {
+            // TODO: better way to do this?
+            let color = (self.rgb.0, self.rgb.1, self.rgb.2, self.alpha);
+            return rgba2hex(color);
+        }
         rgb2hex(self.rgb)
     }
     /// `rgb` string of the color

src/conversion/hex.rs

@@ -1,3 +1,5 @@
+use crate::{helper::round, ALPHA_HEX_MAP};
+
 pub fn rgb2hex(color: (f64, f64, f64)) -> String {
     let (r, g, b) = color;
     let r = r.round() as u8;
@@ -6,6 +8,16 @@ pub fn rgb2hex(color: (f64, f64, f64)) -> String {
     format!("#{:02x}{:02x}{:02x}", r, g, b)
 }
 
+pub fn rgba2hex(color: (f64, f64, f64, f64)) -> String {
+    let (r, g, b, a) = color;
+    let r = r.round() as u8;
+    let g = g.round() as u8;
+    let b = b.round() as u8;
+    let a = round(a, 2).to_string();
+    let a = ALPHA_HEX_MAP.get(a.as_str()).unwrap().to_lowercase();
+    format!("#{:02x}{:02x}{:02x}{}", r, g, b, a)
+}
+
 pub fn hex2rgb(hex: &str) -> (f64, f64, f64) {
     let mut hex = String::from(hex);
     let len = hex.len();
@@ -54,4 +66,27 @@ mod tests {
         let hex = rgb2hex(rgb);
         assert_eq!(hex, "#008080");
     }
+
+    #[test]
+    fn test_rgba2hex() {
+        let rgba = (255.0, 255.0, 255.0, 1.0);
+        let hex = rgba2hex(rgba);
+        assert_eq!(hex, "#ffffffff");
+
+        let rgba = (0.0, 0.0, 0.0, 0.5);
+        let hex = rgba2hex(rgba);
+        assert_eq!(hex, "#00000080");
+
+        let rgba = (0.0, 128.0, 128.0, 0.4);
+        let hex = rgba2hex(rgba);
+        assert_eq!(hex, "#00808066");
+
+        let rgba = (0.0, 128.0, 128.0, 0.23);
+        let hex = rgba2hex(rgba);
+        assert_eq!(hex, "#0080803b");
+
+        let rgba = (0.0, 128.0, 128.0, 0.222222);
+        let hex = rgba2hex(rgba);
+        assert_eq!(hex, "#00808038");
+    }
 }

src/data/alpha_hex_map.rs

@@ -0,0 +1,110 @@
+use std::collections::HashMap;
+
+lazy_static! {
+    /// alpha hex map
+    pub static ref ALPHA_HEX_MAP: HashMap<&'static str, &'static str> = {
+        HashMap::from([
+          ("1", "FF"),
+          ("0.99", "FC"),
+          ("0.98", "FA"),
+          ("0.97", "F7"),
+          ("0.96", "F5"),
+          ("0.95", "F2"),
+          ("0.94", "F0"),
+          ("0.93", "ED"),
+          ("0.92", "EB"),
+          ("0.91", "E8"),
+          ("0.9", "E6"),
+          ("0.89", "E3"),
+          ("0.88", "E0"),
+          ("0.87", "DE"),
+          ("0.86", "DB"),
+          ("0.85", "D9"),
+          ("0.84", "D6"),
+          ("0.83", "D4"),
+          ("0.82", "D1"),
+          ("0.81", "CF"),
+          ("0.8", "CC"),
+          ("0.79", "C9"),
+          ("0.78", "C7"),
+          ("0.77", "C4"),
+          ("0.76", "C2"),
+          ("0.75", "BF"),
+          ("0.74", "BD"),
+          ("0.73", "BA"),
+          ("0.72", "B8"),
+          ("0.71", "B5"),
+          ("0.7", "B3"),
+          ("0.69", "B0"),
+          ("0.68", "AD"),
+          ("0.67", "AB"),
+          ("0.66", "A8"),
+          ("0.65", "A6"),
+          ("0.64", "A3"),
+          ("0.63", "A1"),
+          ("0.62", "9E"),
+          ("0.61", "9C"),
+          ("0.6", "99"),
+          ("0.59", "96"),
+          ("0.58", "94"),
+          ("0.57", "91"),
+          ("0.56", "8F"),
+          ("0.55", "8C"),
+          ("0.54", "8A"),
+          ("0.53", "87"),
+          ("0.52", "85"),
+          ("0.51", "82"),
+          ("0.5", "80"),
+          ("0.49", "7D"),
+          ("0.48", "7A"),
+          ("0.47", "78"),
+          ("0.46", "75"),
+          ("0.45", "73"),
+          ("0.44", "70"),
+          ("0.43", "6E"),
+          ("0.42", "6B"),
+          ("0.41", "69"),
+          ("0.4", "66"),
+          ("0.39", "63"),
+          ("0.38", "61"),
+          ("0.37", "5E"),
+          ("0.36", "5C"),
+          ("0.35", "59"),
+          ("0.34", "57"),
+          ("0.33", "54"),
+          ("0.32", "52"),
+          ("0.31", "4F"),
+          ("0.3", "4D"),
+          ("0.29", "4A"),
+          ("0.28", "47"),
+          ("0.27", "45"),
+          ("0.26", "42"),
+          ("0.25", "40"),
+          ("0.24", "3D"),
+          ("0.23", "3B"),
+          ("0.22", "38"),
+          ("0.21", "36"),
+          ("0.2", "33"),
+          ("0.19", "30"),
+          ("0.18", "2E"),
+          ("0.17", "2B"),
+          ("0.16", "29"),
+          ("0.15", "26"),
+          ("0.14", "24"),
+          ("0.13", "21"),
+          ("0.12", "1F"),
+          ("0.11", "1C"),
+          ("0.1", "1A"),
+          ("0.09", "17"),
+          ("0.08", "14"),
+          ("0.07", "12"),
+          ("0.06", "0F"),
+          ("0.05", "0D"),
+          ("0.04", "0A"),
+          ("0.03", "08"),
+          ("0.02", "05"),
+          ("0.01", "03"),
+          ("0.0", "00"),
+        ])
+    };
+}

src/data/mod.rs

@@ -1 +1,2 @@
+pub mod alpha_hex_map;
 pub mod w3cx11;

src/lib.rs

@@ -24,4 +24,5 @@ pub use color::Color;
 pub use color_calc::blend::*;
 pub use color_calc::distance::*;
 pub use color_space::ColorSpace;
+use data::alpha_hex_map::ALPHA_HEX_MAP;
 use data::w3cx11::W3CX11_HASHMAP as W3CX11;