From 79992723298184d160bb890ad91f9f4e2fbb2503 Mon Sep 17 00:00:00 2001
From: kimikage <kimikage.ceo@gmail.com>
Date: Fri, 6 Aug 2021 12:58:55 +0900
Subject: [PATCH] [WIP] Modify `MSC` and `find_maximum_chroma` interfaces

---
 src/algorithms.jl | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/src/algorithms.jl b/src/algorithms.jl
index ea581d9c..15c0cc7a 100644
--- a/src/algorithms.jl
+++ b/src/algorithms.jl
@@ -180,10 +180,11 @@ may also be specified.
     value. This behavior might change in a future release.
 
 """
-function MSC(h)
+MSC(h) = MSC(Float64(h))
+function MSC(h::Float64)
 
     #Wrap h to [0, 360] range
-    h = normalize_hue(Float64(h))
+    h = normalize_hue(h)
 
     #Selecting edge of RGB cube; R=1 G=2 B=3
     # p #variable
@@ -200,8 +201,7 @@ function MSC(h)
     end
     p, t = pt(h)
 
-    alpha=-sind(h)
-    beta=cosd(h)
+    alpha, beta = sincos(-deg2rad(h))
 
     # un & vn are calculated based on reference white (D65)
     un, vn = xyz_to_uv(WP_DEFAULT)
@@ -219,7 +219,7 @@ function MSC(h)
 
     col = ntuple(i -> i == p ? cpc : Float64(i == t), Val(3))
 
-    return convert(LCHuv, RGB(col...))
+    return convert(LCHuv, RGB{Float64}(col...))
 end
 
 
@@ -240,16 +240,15 @@ end
 # This function finds the maximum chroma for the lightness `c.l` and hue `c.h`
 # by means of the binary search. Even though this requires more than 20
 # iterations, somehow, this is fast.
-function find_maximum_chroma(c::C,
-                             low::Real=0.0,
-                             high::Real=180.0) where {T, C<:Union{LCHab{T}, LCHuv{T}}}
+function find_maximum_chroma(c::C) where {T, C<:LCHuv{T}}
+    _find_maximum_chroma(c, convert(T, 0), convert(T, 180))
+end
+function _find_maximum_chroma(c::C, low::T, high::T) where {T, C<:Union{LCHab{T}, LCHuv{T}}}
     err = convert(T, 1e-6)
-    l, h = convert(T, low), convert(T, high)
+    l, h = low, high
     while true
-        h - l < err && return l
-
         mid = convert(T, (l + h) * oftype(l, 0.5))
-        min(mid - l, h - mid) == zero(T) && return l
+        @fastmath min(mid - l, h - mid) < err && break
         lchm = C(c.l, mid, c.h)
         rgbm = xyz_to_linear_rgb(convert(XYZ{T}, lchm))
         clamped = max(red(rgbm), green(rgbm), blue(rgbm)) > 1-err ||
@@ -257,13 +256,16 @@ function find_maximum_chroma(c::C,
         l = clamped ? l : mid
         h = clamped ? mid : h
     end
+    return l
 end
 
 const LAB_HUE_Y = hue(convert(Lab, RGB(1.0, 1.0, 0.0)))
 
-function find_maximum_chroma(c::LCHab{T}) where T
-    maxc = find_maximum_chroma(c, 0.0, 135.0)
-
+function find_maximum_chroma(c::C) where {T, C<:LCHab{T}}
+    find_maximum_chroma(c, convert(T, 0), convert(T, 135))
+end
+function find_maximum_chroma(c::C, low::T, high::T) where {T, C<:LCHab{T}}
+    maxc = _find_maximum_chroma(c, low, high)
     # The sRGB gamut in LCHab space has a *hollow* around the yellow corner.
     # Since the following boundary is based on the D65 white point, the values
     # should be modified on other conditions.