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colorspace: reduce branching and variables in HSL/HSV
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@arrufat
arrufat committed Dec 13, 2024
1 parent b0301dc commit 9d03c9d
Showing 1 changed file with 76 additions and 134 deletions.
210 changes: 76 additions & 134 deletions src/colorspace.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -174,58 +174,42 @@ const RgbFloat = struct {
const min = @min(self.r, @min(self.g, self.b));
const max = @max(self.r, @max(self.g, self.b));
const delta = max - min;
var hsl = Hsl{ .h = 0, .s = 0, .l = 0 };
hsl.l = (max + min) / 2;
if (hsl.l > 0 and hsl.l < 1) {
hsl.s = delta / if (hsl.l < 0.5) 2 * hsl.l else 2 - 2 * hsl.l;
}
if (delta > 0) {
if (max == self.r and max != self.g) {
hsl.h += (self.g - self.b) / delta;
}
if (max == self.g and max != self.b) {
hsl.h += 2 + (self.b - self.r) / delta;
const hue = if (delta == 0) 0 else blk: {
if (max == self.r) {
break :blk (self.g - self.b) / delta;
} else if (max == self.g) {
break :blk 2 + (self.b - self.r) / delta;
} else {
break :blk 4 + (self.r - self.g) / delta;
}
if (max == self.b and max != self.r) {
hsl.h += 4 + (self.r - self.g) / delta;
}
hsl.h *= 60;
}
hsl.h = @mod(hsl.h, 360);
hsl.s = @max(0, @min(1, hsl.s)) * 100;
hsl.l = @max(0, @min(1, hsl.l)) * 100;
return hsl;
};
const l = (max + min) / 2.0;
const s = if (delta == 0) 0 else if (l < 0.5) delta / (2 * l) else delta / (2 - 2 * l);
return .{
.h = @mod(hue * 60.0, 360.0),
.s = @max(0, @min(1, s)) * 100.0,
.l = @max(0, @min(1, l)) * 100.0,
};
}

/// Converts the RGB color into an HSV color.
fn toHsv(self: RgbFloat) Hsv {
var hsv = Hsv{};
const min = @min(self.r, @min(self.g, self.b));
const max = @max(self.r, @max(self.g, self.b));
const delta = max - min;

// hue
if (delta == 0) {
hsv.h = 0;
} else if (max == self.r) {
hsv.h = (self.g - self.b) / delta * 60;
} else if (max == self.g) {
hsv.h = 120 + (self.b - self.r) / delta * 60;
} else {
hsv.h = 240 + (self.r - self.g) / delta * 60;
}
hsv.h = @mod(hsv.h, 360);

// saturation
if (max == 0) {
hsv.s = 0;
} else {
hsv.s = delta / max * 100;
}

// value
hsv.v = max * 100;
return hsv;
return .{
.h = if (delta == 0) 0 else blk: {
if (max == self.r) {
break :blk @mod((self.g - self.b) / delta * 60, 360);
} else if (max == self.g) {
break :blk @mod(120 + (self.b - self.r) / delta * 60, 360);
} else {
break :blk @mod(240 + (self.r - self.g) / delta * 60, 360);
}
},
.s = if (max == 0) 0 else (delta / max) * 100,
.v = max * 100,
};
}

/// Converts the RGB color into a CIE 1931 XYZ color.
Expand Down Expand Up @@ -470,46 +454,36 @@ pub const Hsl = struct {
}
/// Converts the HSL color into an RGB color, where each channel ranges from 0 to 1.
fn toRgbFloat(self: Hsl) RgbFloat {
var r: f64 = undefined;
var g: f64 = undefined;
var b: f64 = undefined;
const s = self.s / 100;
const l = self.l / 100;
if (self.h < 120) {
r = (120 - self.h) / 60;
g = self.h / 60;
b = 0;
} else if (self.h < 240) {
r = 0;
g = (240 - self.h) / 60;
b = (self.h - 120) / 60;
} else {
r = (self.h - 240) / 60;
g = 0;
b = (360 - self.h) / 60;
}
r = @min(r, 1);
g = @min(g, 1);
b = @min(b, 1);

r = 2 * s * r + (1 - s);
g = 2 * s * g + (1 - s);
b = 2 * s * b + (1 - s);

if (l < 0.5) {
r *= l;
g *= l;
b *= l;
} else {
r = (1 - l) * r + 2 * l - 1;
g = (1 - l) * g + 2 * l - 1;
b = (1 - l) * b + 2 * l - 1;
}
return .{
.r = @max(0, @min(1, r)),
.g = @max(0, @min(1, g)),
.b = @max(0, @min(1, b)),
const h = @max(0, @min(360, self.h));
const s = @max(0, @min(1, self.s / 100));
const l = @max(0, @min(1, self.l / 100));
const hue_sector = h / 60.0;
const sector: usize = @intFromFloat(hue_sector);
const fractional = hue_sector - @as(f64, @floatFromInt(sector));
const hue_factors = [_][3]f64{
.{ 1, fractional, 0 },
.{ 1 - fractional, 1, 0 },
.{ 0, 1, fractional },
.{ 0, 1 - fractional, 1 },
.{ fractional, 0, 1 },
.{ 1, 0, 1 - fractional },
};
const index = @mod(sector, 6);
const r = lerp(1, 2 * hue_factors[index][0], s);
const g = lerp(1, 2 * hue_factors[index][1], s);
const b = lerp(1, 2 * hue_factors[index][2], s);
return if (l < 0.5)
.{
.r = r * l,
.g = g * l,
.b = b * l,
}
else
.{
.r = lerp(r, 2, l) - 1,
.g = lerp(g, 2, l) - 1,
.b = lerp(b, 2, l) - 1,
};
}

/// Converts the HSL color into an RGB color.
Expand Down Expand Up @@ -584,62 +558,30 @@ pub const Hsv = struct {

/// Converts the HSV color into an RGB color.
pub fn toRgbFloat(self: Hsv) RgbFloat {
var r: f64 = undefined;
var g: f64 = undefined;
var b: f64 = undefined;
const hue = @max(0, @min(1, self.h / 360));
const sat = @max(0, @min(1, self.s / 100));
const val = @max(0, @min(1, self.v / 100));

if (sat == 0.0) {
r = val;
g = val;
b = val;
} else {
const sector = hue * 6;
const index: i32 = @intFromFloat(sector);
const fractional = sector - @as(f64, @floatFromInt(index));
const p = val * (1 - sat);
const q = val * (1 - (sat * fractional));
const t = val * (1 - sat * (1 - fractional));

switch (index) {
0 => {
r = val;
g = t;
b = p;
},
1 => {
r = q;
g = val;
b = p;
},
2 => {
r = p;
g = val;
b = t;
},
3 => {
r = p;
g = q;
b = val;
},
4 => {
r = t;
g = p;
b = val;
},
else => {
r = val;
g = p;
b = q;
},
}
}
if (sat == 0.0) return .{ .r = val, .g = val, .b = val };
const sector = hue * 6;
const index: i32 = @intFromFloat(sector);
const fractional = sector - @as(f64, @floatFromInt(index));
const p = val * (1 - sat);
const q = val * (1 - (sat * fractional));
const t = val * (1 - sat * (1 - fractional));
const colors = [_][3]f64{
.{ val, t, p },
.{ q, val, p },
.{ p, val, t },
.{ p, q, val },
.{ t, p, val },
.{ val, p, q },
};
const idx: usize = @intCast(@mod(index, 6));
return .{
.r = @max(0, @min(1, r)),
.g = @max(0, @min(1, g)),
.b = @max(0, @min(1, b)),
.r = colors[idx][0],
.g = colors[idx][1],
.b = colors[idx][2],
};
}

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