feat: replace HSLuv colors with OKLCh

Cargo.lock

@@ -929,6 +929,17 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3d7b894f5411737b7867f4827955924d7c254fc9f4d91a6aad6b097804b1018b"
 
+[[package]]
+name = "colorutils-rs"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "103c2458789cd7b46e6ed7c7ba1bf969b6569c902e3732843c55962c53eac686"
+dependencies = [
+ "erydanos",
+ "half",
+ "num-traits",
+]
+
 [[package]]
 name = "concurrent-queue"
 version = "2.5.0"
@@ -1299,6 +1310,7 @@ dependencies = [
  "brotli",
  "bytes",
  "chrono",
+ "colorutils-rs",
  "criterion",
  "data-encoding",
  "deltachat-contact-tools",
@@ -1342,7 +1354,6 @@ dependencies = [
  "ratelimit",
  "regex",
  "rusqlite",
- "rust-hsluv",
  "rustls",
  "rustls-pki-types",
  "sanitize-filename",
@@ -1895,6 +1906,15 @@ version = "3.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a5d9305ccc6942a704f4335694ecd3de2ea531b114ac2d51f5f843750787a92f"
 
+[[package]]
+name = "erydanos"
+version = "0.2.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8cbdc4987ed8e9ece64845393c2d53596b3a4ccbfb3948d799d58f6450e89fb1"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "escaper"
 version = "0.1.1"
@@ -2332,9 +2352,9 @@ dependencies = [
 
 [[package]]
 name = "half"
-version = "2.4.0"
+version = "2.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b5eceaaeec696539ddaf7b333340f1af35a5aa87ae3e4f3ead0532f72affab2e"
+checksum = "459196ed295495a68f7d7fe1d84f6c4b7ff0e21fe3017b2f283c6fac3ad803c9"
 dependencies = [
  "cfg-if",
  "crunchy",
@@ -5059,12 +5079,6 @@ dependencies = [
  "smallvec",
 ]
 
-[[package]]
-name = "rust-hsluv"
-version = "0.1.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "efe2374f2385cdd8755a446f80b2a646de603c9d8539ca38734879b5c71e378b"
-
 [[package]]
 name = "rustc-demangle"
 version = "0.1.24"

Cargo.toml

@@ -49,9 +49,11 @@ async-native-tls = { version = "0.5", default-features = false, features = ["run
 async-smtp = { version = "0.10.2", default-features = false, features = ["runtime-tokio"] }
 async_zip = { version = "0.0.17", default-features = false, features = ["deflate", "tokio-fs"] }
 base64 = { workspace = true }
+blake3 = "1.8.2"
 brotli = { version = "8", default-features=false, features = ["std"] }
 bytes = "1"
 chrono = { workspace = true, features = ["alloc", "clock", "std"] }
+colorutils-rs = { version = "0.7.5", default-features = false }
 data-encoding = "2.9.0"
 escaper = "0.1"
 fast-socks5 = "0.10"
@@ -85,7 +87,6 @@ quoted_printable = "0.5"
 rand = { workspace = true }
 regex = { workspace = true }
 rusqlite = { workspace = true, features = ["sqlcipher"] }
-rust-hsluv = "0.1"
 rustls-pki-types = "1.12.0"
 rustls = { version = "0.23.22", default-features = false }
 sanitize-filename = { workspace = true }
@@ -112,7 +113,6 @@ tracing = "0.1.41"
 url = "2"
 uuid = { version = "1", features = ["serde", "v4"] }
 webpki-roots = "0.26.8"
-blake3 = "1.8.2"
 
 [dev-dependencies]
 anyhow = { workspace = true, features = ["backtrace"] } # Enable `backtrace` feature in tests.

src/chat/chat_tests.rs

@@ -32,7 +32,7 @@ async fn test_chat_info() {
   "archived": false,
   "param": "",
   "is_sending_locations": false,
-  "color": 35391,
+  "color": 29377,
   "profile_image": {},
   "draft": "",
   "is_muted": false,
@@ -1931,7 +1931,7 @@ async fn test_chat_get_color() -> Result<()> {
     let t = TestContext::new().await;
     let chat_id = create_group_ex(&t, None, "a chat").await?;
     let color1 = Chat::load_from_db(&t, chat_id).await?.get_color(&t).await?;
-    assert_eq!(color1, 0x008772);
+    assert_eq!(color1, 0x613dd7);
 
     // upper-/lowercase makes a difference for the colors, these are different groups
     // (in contrast to email addresses, where upper-/lowercase is ignored in practise)

src/color.rs

@@ -1,38 +1,42 @@
-//! Implementation of Consistent Color Generation.
+//! Color generation.
 //!
-//! Consistent Color Generation is defined in XEP-0392.
+//! This is similar to Consistent Color Generation defined in XEP-0392,
+//! but uses OKLCh colorspace instead of HSLuv
+//! to ensure that colors have the same lightness.
 //!
 //! Color Vision Deficiency correction is not implemented as Delta Chat does not offer
 //! corresponding settings.
-use hsluv::hsluv_to_rgb;
+use colorutils_rs::{Oklch, Rgb, TransferFunction};
 use sha1::{Digest, Sha1};
 
 /// Converts an identifier to Hue angle.
-fn str_to_angle(s: &str) -> f64 {
+fn str_to_angle(s: &str) -> f32 {
     let bytes = s.as_bytes();
     let result = Sha1::digest(bytes);
     let checksum: u16 = result.first().map_or(0, |&x| u16::from(x))
         + 256 * result.get(1).map_or(0, |&x| u16::from(x));
-    f64::from(checksum) / 65536.0 * 360.0
+    f32::from(checksum) / 65536.0 * 360.0
 }
 
 /// Converts RGB tuple to a 24-bit number.
 ///
 /// Returns a 24-bit number with 8 least significant bits corresponding to the blue color and 8
 /// most significant bits corresponding to the red color.
-fn rgb_to_u32((r, g, b): (f64, f64, f64)) -> u32 {
+fn rgb_to_u32(rgb: Rgb<u8>) -> u32 {
-    let r = ((r * 256.0) as u32).min(255);
+    65536 * u32::from(rgb.r) + 256 * u32::from(rgb.g) + u32::from(rgb.b)
-    let g = ((g * 256.0) as u32).min(255);
-    let b = ((b * 256.0) as u32).min(255);
-    65536 * r + 256 * g + b
 }
 
 /// Converts an identifier to RGB color.
 ///
-/// Saturation is set to maximum (100.0) to make colors distinguishable, and lightness is set to
+/// Lightness is set to half (0.5) to make colors suitable both for light and dark theme.
-/// half (50.0) to make colors suitable both for light and dark theme.
 pub fn str_to_color(s: &str) -> u32 {
-    rgb_to_u32(hsluv_to_rgb((str_to_angle(s), 100.0, 50.0)))
+    let lightness = 0.5;
+    let chroma = 0.22;
+    let angle = str_to_angle(s);
+    let oklch = Oklch::new(lightness, chroma, angle);
+    let rgb = oklch.to_rgb(TransferFunction::Srgb);
+
+    rgb_to_u32(rgb)
 }
 
 /// Returns color as a "#RRGGBB" `String` where R, G, B are hex digits.
@@ -45,6 +49,7 @@ mod tests {
     use super::*;
 
     #[test]
+    #[allow(clippy::excessive_precision)]
     fn test_str_to_angle() {
         // Test against test vectors from
         // <https://xmpp.org/extensions/xep-0392.html#testvectors-fullrange-no-cvd>
@@ -57,11 +62,11 @@ mod tests {
 
     #[test]
     fn test_rgb_to_u32() {
-        assert_eq!(rgb_to_u32((0.0, 0.0, 0.0)), 0);
+        assert_eq!(rgb_to_u32(Rgb::new(0, 0, 0)), 0);
-        assert_eq!(rgb_to_u32((1.0, 1.0, 1.0)), 0xffffff);
+        assert_eq!(rgb_to_u32(Rgb::new(0xff, 0xff, 0xff)), 0xffffff);
-        assert_eq!(rgb_to_u32((0.0, 0.0, 1.0)), 0x0000ff);
+        assert_eq!(rgb_to_u32(Rgb::new(0, 0, 0xff)), 0x0000ff);
-        assert_eq!(rgb_to_u32((0.0, 1.0, 0.0)), 0x00ff00);
+        assert_eq!(rgb_to_u32(Rgb::new(0, 0xff, 0)), 0x00ff00);
-        assert_eq!(rgb_to_u32((1.0, 0.0, 0.0)), 0xff0000);
+        assert_eq!(rgb_to_u32(Rgb::new(0xff, 0, 0)), 0xff0000);
-        assert_eq!(rgb_to_u32((1.0, 0.5, 0.0)), 0xff8000);
+        assert_eq!(rgb_to_u32(Rgb::new(0xff, 0x80, 0)), 0xff8000);
     }
 }

src/contact/contact_tests.rs

@@ -759,7 +759,7 @@ async fn test_contact_get_color() -> Result<()> {
     let t = TestContext::new().await;
     let contact_id = Contact::create(&t, "name", "name@example.net").await?;
     let color1 = Contact::get_by_id(&t, contact_id).await?.get_color();
-    assert_eq!(color1, 0xA739FF);
+    assert_eq!(color1, 0x4947dc);
 
     let t = TestContext::new().await;
     let contact_id = Contact::create(&t, "prename name", "name@example.net").await?;