From 7a1b43c6f1b970164c07ee1cc8efb8719ea0f8b4 Mon Sep 17 00:00:00 2001
From: Imbris <imbrisf@gmail.com>
Date: Mon, 13 Jan 2020 23:19:38 -0500
Subject: [PATCH] Branch on lower color values for more accurate speedy color
 conversion, add simple color conversion benchmarks

---
 common/Cargo.toml                 |  4 ++++
 common/benches/chonk_benchmark.rs |  5 ++---
 common/benches/color_benchmark.rs | 22 ++++++++++++++++++++++
 common/src/util/mod.rs            | 22 +++++++++++++++++-----
 4 files changed, 45 insertions(+), 8 deletions(-)
 create mode 100644 common/benches/color_benchmark.rs

diff --git a/common/Cargo.toml b/common/Cargo.toml
index adcdd3f834..6559126368 100644
--- a/common/Cargo.toml
+++ b/common/Cargo.toml
@@ -37,3 +37,7 @@ criterion = "0.3"
 [[bench]]
 name = "chonk_benchmark"
 harness = false
+
+[[bench]]
+name = "color_benchmark"
+harness = false
diff --git a/common/benches/chonk_benchmark.rs b/common/benches/chonk_benchmark.rs
index ee803378cb..d325f02888 100644
--- a/common/benches/chonk_benchmark.rs
+++ b/common/benches/chonk_benchmark.rs
@@ -1,7 +1,6 @@
-#[macro_use]
-extern crate criterion;
-
 use criterion::black_box;
+use criterion::criterion_group;
+use criterion::criterion_main;
 use criterion::Criterion;
 
 use vek::*;
diff --git a/common/benches/color_benchmark.rs b/common/benches/color_benchmark.rs
new file mode 100644
index 0000000000..5031cb4c06
--- /dev/null
+++ b/common/benches/color_benchmark.rs
@@ -0,0 +1,22 @@
+use criterion::black_box;
+use criterion::criterion_group;
+use criterion::criterion_main;
+use criterion::Criterion;
+
+use vek::*;
+use veloren_common::util::{linear_to_srgb, srgb_to_linear};
+
+fn criterion_benchmark(c: &mut Criterion) {
+    c.bench_function("color: srgb to linear (0.5, 0.1, 0.5)", |b| {
+        b.iter(|| {
+            black_box(srgb_to_linear(black_box(Rgb::new(0.5, 0.1, 0.5))));
+        })
+    });
+    c.bench_function("color: linear to srgb (0.5, 0.1, 0.5)", |b| {
+        b.iter(|| {
+            black_box(linear_to_srgb(black_box(Rgb::new(0.5, 0.1, 0.5))));
+        })
+    });
+}
+criterion_group!(benches, criterion_benchmark);
+criterion_main!(benches);
diff --git a/common/src/util/mod.rs b/common/src/util/mod.rs
index 37f726b938..5f49bf49ef 100644
--- a/common/src/util/mod.rs
+++ b/common/src/util/mod.rs
@@ -9,14 +9,26 @@ use vek::{Mat3, Rgb, Rgba, Vec3};
 
 #[inline(always)]
 pub fn srgb_to_linear(col: Rgb<f32>) -> Rgb<f32> {
-    0.012522878 * col + 0.682171111 * col * col + 0.305306011 * col * col * col
+    col.map(|c| {
+        if c <= 0.104 {
+            c * 0.08677088
+        } else {
+            0.012522878 * c + 0.682171111 * c * c + 0.305306011 * c * c * c
+        }
+    })
 }
 #[inline(always)]
 pub fn linear_to_srgb(col: Rgb<f32>) -> Rgb<f32> {
-    let s1 = col.sqrt();
-    let s2 = s1.sqrt();
-    let s3 = s2.sqrt();
-    0.585122381 * s1 + 0.783140355 * s2 - 0.368262736 * s3
+    col.map(|c| {
+        if c <= 0.0060 {
+            c * 11.500726
+        } else {
+            let s1 = c.sqrt();
+            let s2 = s1.sqrt();
+            let s3 = s2.sqrt();
+            0.585122381 * s1 + 0.783140355 * s2 - 0.368262736 * s3
+        }
+    })
 }
 #[inline(always)]
 pub fn srgba_to_linear(col: Rgba<f32>) -> Rgba<f32> {