Implement Consistent Color Generation (XEP-0392)

Cargo.toml

@@ -17,6 +17,7 @@ deltachat_derive = { path = "./deltachat_derive" }
 libc = "0.2.51"
 pgp = { version = "0.7.0", default-features = false } 
 hex = "0.4.0"
+sha-1 = "0.9.3"
 sha2 = "0.9.0"
 rand = "0.7.0"
 smallvec = "1.0.0"
@@ -64,6 +65,7 @@ url = "2.1.1"
 async-std-resolver = "0.19.5"
 async-tar = "0.3.0"
 uuid = { version = "0.8", features = ["serde", "v4"] }
+rust-hsluv = "0.1.4"
 
 pretty_env_logger = { version = "0.4.0", optional = true }
 log = {version = "0.4.8", optional = true }

src/chat.rs

@@ -15,6 +15,7 @@ use serde::{Deserialize, Serialize};
 use crate::aheader::EncryptPreference;
 use crate::blob::{BlobError, BlobObject};
 use crate::chatlist::dc_get_archived_cnt;
+use crate::color::str_to_color;
 use crate::config::Config;
 use crate::constants::{
     Blocked, Chattype, ShowEmails, Viewtype, DC_CHAT_ID_ALLDONE_HINT, DC_CHAT_ID_ARCHIVED_LINK,
@@ -26,8 +27,8 @@ use crate::contact::{addr_cmp, Contact, Origin, VerifiedStatus};
 use crate::context::Context;
 use crate::dc_tools::{
     dc_create_id, dc_create_outgoing_rfc724_mid, dc_create_smeared_timestamp,
-    dc_create_smeared_timestamps, dc_get_abs_path, dc_gm2local_offset, dc_str_to_color,
-    improve_single_line_input, time, IsNoneOrEmpty,
+    dc_create_smeared_timestamps, dc_get_abs_path, dc_gm2local_offset, improve_single_line_input,
+    time, IsNoneOrEmpty,
 };
 use crate::ephemeral::{delete_expired_messages, schedule_ephemeral_task, Timer as EphemeralTimer};
 use crate::events::EventType;
@@ -891,7 +892,7 @@ impl Chat {
                 }
             }
         } else {
-            color = dc_str_to_color(&self.name);
+            color = str_to_color(&self.name);
         }
 
         color
@@ -3081,7 +3082,7 @@ mod tests {
                 "param": "",
                 "gossiped_timestamp": 0,
                 "is_sending_locations": false,
-                "color": 15895624,
+                "color": 35391,
                 "profile_image": "",
                 "draft": "",
                 "is_muted": false,

src/color.rs

@@ -0,0 +1,46 @@
+//! Implementation of Consistent Color Generation
+//!
+//! Consistent Color Generation is defined in XEP-0392.
+//!
+//! Color Vision Deficiency correction is not implemented as Delta Chat does not offer
+//! corresponding settings.
+use hsluv::hsluv_to_rgb;
+use sha1::{Digest, Sha1};
+
+/// Converts an identifier to Hue angle.
+fn str_to_angle(s: impl AsRef<str>) -> f64 {
+    let bytes = s.as_ref().as_bytes();
+    let result = Sha1::digest(bytes);
+    let checksum: u16 = result.get(0).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
+}
+
+/// Converts an identifier to RGB color.
+///
+/// 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.
+///
+/// Saturation is set to maximum (100.0) to make colors distinguishable, and lightness is set to
+/// half (50.0) to make colors suitable both for light and dark theme.
+pub(crate) fn str_to_color(s: impl AsRef<str>) -> u32 {
+    let (r, g, b) = hsluv_to_rgb((str_to_angle(s), 100.0, 50.0));
+    65536 * (r * 256.0) as u32 + 256 * (g * 256.0) as u32 + (b * 256.0) as u32
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[allow(clippy::float_cmp)]
+    #[test]
+    fn test_str_to_angle() {
+        // Test against test vectors from
+        // https://xmpp.org/extensions/xep-0392.html#testvectors-fullrange-no-cvd
+        assert!((str_to_angle("Romeo") - 327.255249).abs() < 1e-6);
+        assert!((str_to_angle("juliet@capulet.lit") - 209.410400).abs() < 1e-6);
+        assert!((str_to_angle("😺") - 331.199341).abs() < 1e-6);
+        assert!((str_to_angle("council") - 359.994507).abs() < 1e-6);
+        assert!((str_to_angle("Board") - 171.430664).abs() < 1e-6);
+    }
+}

src/contact.rs

@@ -9,15 +9,14 @@ use regex::Regex;
 
 use crate::aheader::EncryptPreference;
 use crate::chat::ChatId;
+use crate::color::str_to_color;
 use crate::config::Config;
 use crate::constants::{
     Chattype, DC_CHAT_ID_DEADDROP, DC_CONTACT_ID_DEVICE, DC_CONTACT_ID_DEVICE_ADDR,
     DC_CONTACT_ID_LAST_SPECIAL, DC_CONTACT_ID_SELF, DC_GCL_ADD_SELF, DC_GCL_VERIFIED_ONLY,
 };
 use crate::context::Context;
-use crate::dc_tools::{
-    dc_get_abs_path, dc_str_to_color, improve_single_line_input, listflags_has, EmailAddress,
-};
+use crate::dc_tools::{dc_get_abs_path, improve_single_line_input, listflags_has, EmailAddress};
 use crate::events::EventType;
 use crate::key::{DcKey, SignedPublicKey};
 use crate::login_param::LoginParam;
@@ -947,7 +946,7 @@ impl Contact {
     /// and can be used for an fallback avatar with white initials
     /// as well as for headlines in bubbles of group chats.
     pub fn get_color(&self) -> u32 {
-        dc_str_to_color(&self.addr)
+        str_to_color(&self.addr)
     }
 
     /// Gets the contact's status.

src/dc_tools.rs

@@ -48,31 +48,6 @@ pub(crate) fn dc_truncate(buf: &str, approx_chars: usize) -> Cow<str> {
     }
 }
 
-/// the colors must fulfill some criterions as:
-/// - contrast to black and to white
-/// - work as a text-color
-/// - being noticeable on a typical map
-/// - harmonize together while being different enough
-/// (therefore, we cannot just use random rgb colors :)
-const COLORS: [u32; 16] = [
-    0xe5_65_55, 0xf2_8c_48, 0x8e_85_ee, 0x76_c8_4d, 0x5b_b6_cc, 0x54_9c_dd, 0xd2_5c_99, 0xb3_78_00,
-    0xf2_30_30, 0x39_b2_49, 0xbb_24_3b, 0x96_40_78, 0x66_87_4f, 0x30_8a_b9, 0x12_7e_d0, 0xbe_45_0c,
-];
-
-#[allow(clippy::indexing_slicing)]
-pub(crate) fn dc_str_to_color(s: impl AsRef<str>) -> u32 {
-    let str_lower = s.as_ref().to_lowercase();
-    let mut checksum = 0;
-    let bytes = str_lower.as_bytes();
-    for (i, byte) in bytes.iter().enumerate() {
-        checksum += (i + 1) * *byte as usize;
-        checksum %= 0x00ff_ffff;
-    }
-    let color_index = checksum % COLORS.len();
-
-    COLORS[color_index]
-}
-
 /* ******************************************************************************
  * date/time tools
  ******************************************************************************/

src/lib.rs

@@ -77,6 +77,7 @@ pub mod stock_str;
 mod token;
 #[macro_use]
 mod dehtml;
+mod color;
 pub mod html;
 pub mod plaintext;