Replace delta_e depedency with empfindung

This removes dependency on ancient lab versions which we were forced to
use due to delta_e lack of maintenance.

Issue: #6

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name          = "ansi_colours"
 description   = "true-colour ↔ ANSI terminal palette converter"
-version       = "1.0.3"
+version       = "1.0.4"
 readme        = "README.md"
 authors       = ["Michał Nazarewicz <mina86@mina86.com>"]
 keywords      = ["ansi", "terminal", "color", "rgb"]
@@ -16,8 +16,8 @@ edition       = "2018"
 maintenance = { status = "actively-developed" }
 
 [dev-dependencies]
-delta_e = "^0.2"
-lab = "0.*"
+empfindung = "0.2"
+lab = ">=0.4, <1.0"
 
 [build-dependencies]
 cc = "^1.0"

tests/ansi256.rs

@@ -1,8 +1,3 @@
-extern crate delta_e;
-extern crate lab;
-
-extern crate ansi_colours;
-
 fn to_rgb(index: u8) -> (u8, u8, u8) {
     ansi_colours::rgb_from_ansi256(index)
 }
@@ -57,7 +52,7 @@ fn best_grey(y: u8) -> u8 {
         .map(|(idx, v)| (*v, idx as u8 * (36 + 6 + 1) + 16))
         .chain((0..24u8).map(|idx| (idx * 10 + 8, idx + 232)))
         .fold((f32::INFINITY, 0), |best, elem| {
-            let d = delta_e::DE2000::from_rgb(&grey, &[elem.0, elem.0, elem.0]);
+            let d = empfindung::de2000::diff_rgb(&grey, &[elem.0, elem.0, elem.0]);
             if d < best.0 {
                 (d, elem.1)
             } else {

tools/Cargo.toml

@@ -6,7 +6,5 @@ publish = false
 edition = "2018"
 
 [dependencies]
-delta_e = "^0.2"
-# delta_e uses lab 0.7 so we cannot go up to 0.8
-# https://github.com/elliotekj/DeltaE/pull/5
-lab = "^0.7"
+empfindung = "0.2"
+lab = ">=0.4, <1.0"

tools/src/bin/cube.rs

@@ -14,13 +14,10 @@
 // You should have received a copy of the GNU Lesser General Public License
 // along with ansi_colours.  If not, see <http://www.gnu.org/licenses/>.
 
-extern crate delta_e;
-extern crate lab;
-
 static CUBE_VALUES: [u8; 6] = [0, 95, 135, 175, 215, 255];
 
 fn distance(x: &lab::Lab, y: (u8, u8, u8)) -> f32 {
-    delta_e::DE2000::new(*x, lab::Lab::from_rgb(&[y.0, y.1, y.2]))
+    empfindung::de2000::diff(*x, lab::Lab::from_rgb(&[y.0, y.1, y.2]))
 }
 
 fn find_best<F: Fn(u8) -> (u8, u8, u8)>(component: &'static str, to_rgb: F) {