Use ansi_colours package for better true-colour approximation

Cargo.lock

@@ -6,6 +6,14 @@ dependencies = [
  "memchr 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "ansi_colours"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cc 1.0.25 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "ansi_term"
 version = "0.11.0"
@@ -37,6 +45,7 @@ dependencies = [
 name = "bat"
 version = "0.7.0"
 dependencies = [
+ "ansi_colours 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -794,6 +803,7 @@ dependencies = [
 
 [metadata]
 "checksum aho-corasick 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)" = "68f56c7353e5a9547cbd76ed90f7bb5ffc3ba09d4ea9bd1d8c06c8b1142eeb5a"
+"checksum ansi_colours 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "1d0f302a81afc6a7f4350c04f0ba7cfab529cc009bca3324b3fb5764e6add8b6"
 "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
 "checksum atty 0.2.11 (registry+https://github.com/rust-lang/crates.io-index)" = "9a7d5b8723950951411ee34d271d99dddcc2035a16ab25310ea2c8cfd4369652"
 "checksum base64 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7c4a342b450b268e1be8036311e2c613d7f8a7ed31214dff1cc3b60852a3168d"

Cargo.toml

@@ -16,6 +16,7 @@ exclude = [
 [dependencies]
 atty = "0.2.2"
 ansi_term = "0.11"
+ansi_colours = "^1.0"
 console = "0.6"
 directories = "1.0"
 lazy_static = "1.0"

src/terminal.rs

@@ -1,32 +1,15 @@
+extern crate ansi_colours;
+
 use ansi_term::Colour::{Fixed, RGB};
 use ansi_term::{self, Style};
 
 use syntect::highlighting::{self, FontStyle};
 
-/// Approximate a 24 bit color value by a 8 bit ANSI code
-fn rgb2ansi(r: u8, g: u8, b: u8) -> u8 {
-    const BLACK: u8 = 16;
-    const WHITE: u8 = 231;
-
-    if r == g && g == b {
-        if r < 8 {
-            BLACK
-        } else if r > 248 {
-            WHITE
-        } else {
-            ((r - 8) as u16 * 24 / 247) as u8 + 232
-        }
-    } else {
-        36 * (r / 51) + 6 * (g / 51) + (b / 51) + 16
-    }
-}
-
 pub fn to_ansi_color(color: highlighting::Color, true_color: bool) -> ansi_term::Colour {
     if true_color {
         RGB(color.r, color.g, color.b)
     } else {
-        let ansi_code = rgb2ansi(color.r, color.g, color.b);
+        Fixed(ansi_colours::ansi256_from_rgb((color.r, color.g, color.b)))
-        Fixed(ansi_code)
     }
 }
 
@@ -54,27 +37,3 @@ pub fn as_terminal_escaped(
 
     style.paint(text).to_string()
 }
-
-#[test]
-fn test_rgb2ansi_black_white() {
-    assert_eq!(16, rgb2ansi(0x00, 0x00, 0x00));
-    assert_eq!(231, rgb2ansi(0xff, 0xff, 0xff));
-}
-
-#[test]
-fn test_rgb2ansi_gray() {
-    assert_eq!(241, rgb2ansi(0x6c, 0x6c, 0x6c));
-    assert_eq!(233, rgb2ansi(0x1c, 0x1c, 0x1c));
-}
-
-#[test]
-fn test_rgb2ansi_color() {
-    assert_eq!(96, rgb2ansi(0x87, 0x5f, 0x87));
-    assert_eq!(141, rgb2ansi(0xaf, 0x87, 0xff));
-    assert_eq!(193, rgb2ansi(0xd7, 0xff, 0xaf));
-}
-
-#[test]
-fn test_rgb2ansi_approx() {
-    assert_eq!(231, rgb2ansi(0xfe, 0xfe, 0xfe));
-}