From 80ac29e7cdcfdc1728c92047ea571cb01dc9f626 Mon Sep 17 00:00:00 2001
From: Meghan Denny <hello@nektro.net>
Date: Thu, 14 Sep 2023 20:22:25 -0700
Subject: [PATCH] add HSL

---
 HSL.zig  | 26 ++++++++++++++++++++++++++
 mod.zig  |  1 +
 sRGB.zig | 19 +++++++++++++++++++
 x.zig    |  3 +++
 4 files changed, 49 insertions(+)
 create mode 100644 HSL.zig
 create mode 100644 x.zig

diff --git a/HSL.zig b/HSL.zig
new file mode 100644
index 0000000000000000000000000000000000000000..e88ad72d5c87b33b6db69088fbda5da5512545de
--- /dev/null
+++ b/HSL.zig
@@ -0,0 +1,26 @@
+//! object representing a single color in the HSL colorspace with h channel value from 0-360 and s,l channel values from 0-1
+
+const std = @import("std");
+const Self = @This();
+
+h: f32, // hue
+s: f32, // saturation
+l: f32, // luminance
+a: f32, // alpha
+
+pub fn initHSLA(h: f32, s: f32, l: f32, a: f32) Self {
+    std.debug.assert(h >= 0.0 and h <= 1.0);
+    std.debug.assert(s >= 0.0 and s <= 1.0);
+    std.debug.assert(l >= 0.0 and l <= 1.0);
+    std.debug.assert(a >= 0.0 and a <= 1.0);
+    return Self{
+        .h = h,
+        .s = s,
+        .l = l,
+        .a = a,
+    };
+}
+
+pub fn eql(x: Self, y: Self) bool {
+    return x.h == y.h and x.s == y.s and x.l == y.l and x.a == y.a;
+}
diff --git a/mod.zig b/mod.zig
index 0ec6c5ec197751f5b06dd8dee9af7de1fbe07c3c..621e3dcdf45a9f1b7de0842ba0dac64e832ed6cd 100644
--- a/mod.zig
+++ b/mod.zig
@@ -4,3 +4,4 @@ const color = @This();
 pub const sRGB = @import("./sRGB.zig");
 pub const LinearRgb = @import("./LinearRgb.zig");
 pub const CMYK = @import("./CMYK.zig");
+pub const HSL = @import("./HSL.zig");
diff --git a/sRGB.zig b/sRGB.zig
index 20b9cb019ad8591ccee5352062a45906b821a170..a93e9cfeab7ce6db934e8aa91b4570756a964ce1 100644
--- a/sRGB.zig
+++ b/sRGB.zig
@@ -3,6 +3,7 @@
 const std = @import("std");
 const Self = @This();
 const color = @import("./mod.zig");
+const _x = @import("./x.zig");
 
 r: u8, // red value
 g: u8, // green value
@@ -107,3 +108,21 @@ pub fn to_cmyk(x: Self) color.CMYK {
     const a = f.a;
     return color.CMYK.initCMYKA(c, m, y, k, a);
 }
+
+pub fn to_hsl(x: Self) color.HSL {
+    const f = x.to_float();
+    const cmax = @max(f.r, f.g, f.b);
+    const cmin = @min(f.r, f.g, f.b);
+    const delta = cmax - cmin;
+    const h = blk: {
+        if (delta == 0) break :blk 0;
+        if (cmax == f.r) break :blk ((((f.g - f.b) / delta) % 6) * 60) % 360;
+        if (cmax == f.g) break :blk ((((f.b - f.r) / delta) + 2) * 60) % 360;
+        if (cmax == f.b) break :blk ((((f.r - f.g) / delta) + 4) * 60) % 360;
+        unreachable;
+    };
+    const l = (cmax + cmin) / 2;
+    const s = if (delta == 0) 0 else delta / (1 - _x.abs(2 * l - 1));
+    const a = f.a;
+    return color.HSL.initHSLA(h, s, l, a);
+}
diff --git a/x.zig b/x.zig
new file mode 100644
index 0000000000000000000000000000000000000000..04b5125dc952773a5e972841ba06962a14d0aade
--- /dev/null
+++ b/x.zig
@@ -0,0 +1,3 @@
+pub fn abs(x: f32) f32 {
+    return if (x < 0.0) -x else x;
+}
-- 
2.54.0