culors 1.6.0

Rust port of the culori color library. Color spaces, CSS Color Module 4 parsing, interpolation, gamut mapping, ΔE, blending, filters.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374

//! `clamp_gamut` (naïve per-channel clip) and `clamp_chroma` (chroma
//! bisection in an LCh-like space). Both mirror culori 4.0.2's `clamp.js`.

use crate::gamut::in_gamut::{
    color_to_a98, color_to_p3, color_to_prophoto, color_to_rec2020, color_to_rgb, in_gamut,
};
use crate::spaces::{Hsl, Hsv, Hwb, Lch, LinearRgb, Oklch, ProphotoRgb, Rec2020, Rgb, A98, P3};
use crate::Color;

/// Naïve per-channel clamp into the gamut named by `mode`.
///
/// Mirrors culori's `clampGamut(mode)`: convert the color to the gamut's
/// underlying RGB space, clamp each channel to `[0, 1]`, then convert back
/// to the source mode. For `mode` values without a gamut definition
/// (`lab`/`lch`/`oklab`/`oklch`/`xyz*`/`jab`/`jch`/`dlab`/`dlch`/`itp`/
/// `xyb`/`luv`/`lchuv`/`cubehelix`/`yiq`/`lab65`/`lch65`) the input is
/// returned as-is, matching culori's `if (!gamut) return color => prepare(color)`.
///
/// The output stays in the source mode (the variant of the input
/// `Color`). Hue is not preserved — per-channel clipping shifts both
/// chroma and hue.
pub fn clamp_gamut(color: Color, mode: &str) -> Color {
    match mode {
        // gamut: 'rgb' — sRGB cylindricals plus the cylindrical-look-alikes
        // (`hsi`, `okhsl`, `okhsv`) and the culors-only spaces that route
        // their gamut check through rgb.
        "rgb" | "hsl" | "hsv" | "hwb" | "hsi" | "okhsl" | "okhsv" | "hsluv" | "hpluv"
        | "prismatic" => {
            if in_gamut(&color, mode) {
                return color;
            }
            let clamped_rgb = clamp_rgb_channels(color_to_rgb(color));
            convert_rgb_back_to_source_mode(clamped_rgb, color)
        }
        // gamut: true on `lrgb` — clamp on linear-RGB channels.
        "lrgb" => {
            if in_gamut(&color, mode) {
                return color;
            }
            let v = match color {
                Color::LinearRgb(x) => x,
                other => crate::convert::convert::<crate::spaces::Xyz65, crate::spaces::LinearRgb>(
                    to_xyz65(other),
                ),
            };
            let clamped = crate::spaces::LinearRgb {
                r: clamp01(v.r),
                g: clamp01(v.g),
                b: clamp01(v.b),
                alpha: v.alpha,
            };
            // Same source mode short-circuit; otherwise round-trip via XYZ.
            if let Color::LinearRgb(_) = color {
                Color::LinearRgb(clamped)
            } else {
                let xyz = to_xyz65(Color::LinearRgb(clamped));
                from_xyz65_in_mode_of(xyz, color)
            }
        }
        "p3" => clamp_wide_gamut(color, mode, color_to_p3, |v| {
            Color::P3(P3 {
                r: clamp01(v.r),
                g: clamp01(v.g),
                b: clamp01(v.b),
                alpha: v.alpha,
            })
        }),
        "rec2020" => clamp_wide_gamut(color, mode, color_to_rec2020, |v| {
            Color::Rec2020(Rec2020 {
                r: clamp01(v.r),
                g: clamp01(v.g),
                b: clamp01(v.b),
                alpha: v.alpha,
            })
        }),
        "a98" => clamp_wide_gamut(color, mode, color_to_a98, |v| {
            Color::A98(A98 {
                r: clamp01(v.r),
                g: clamp01(v.g),
                b: clamp01(v.b),
                alpha: v.alpha,
            })
        }),
        "prophoto" => clamp_wide_gamut(color, mode, color_to_prophoto, |v| {
            Color::ProphotoRgb(ProphotoRgb {
                r: clamp01(v.r),
                g: clamp01(v.g),
                b: clamp01(v.b),
                alpha: v.alpha,
            })
        }),
        // No gamut definition in culori — pass through. Mirrors culori's
        // `if (!gamut) return color => prepare(color)`.
        "lab" | "lab65" | "lch" | "lch65" | "oklab" | "oklch" | "xyz50" | "xyz65" | "jab"
        | "jch" | "dlab" | "dlch" | "itp" | "xyb" | "luv" | "lchuv" | "cubehelix" | "yiq" => color,
        // Truly unknown — degrade through rgb rather than panic.
        _ => {
            if in_gamut(&color, "rgb") {
                return color;
            }
            let clamped_rgb = clamp_rgb_channels(color_to_rgb(color));
            convert_rgb_back_to_source_mode(clamped_rgb, color)
        }
    }
}

// Generic wide-gamut clamp helper. Converts the input to the destination
// gamut, returns the original if already in gamut, else clamps each
// channel to [0, 1] and converts back to the source mode. Mirrors
// culori's `clampGamut('p3' | 'rec2020' | …)`.
fn clamp_wide_gamut<T, F, C>(color: Color, mode: &str, to_dest: F, clamp_channels: C) -> Color
where
    F: Fn(Color) -> T,
    C: Fn(T) -> Color,
{
    if in_gamut(&color, mode) {
        return color;
    }
    let dest_color = clamp_channels(to_dest(color));
    convert_color_back_to_source_mode(dest_color, color)
}

// Convert `dest_color` (already in the wide-gamut destination space) back
// to the source `template`'s mode. Falls back to round-tripping through
// XYZ65 when the source mode differs from the destination.
fn convert_color_back_to_source_mode(dest_color: Color, template: Color) -> Color {
    if std::mem::discriminant(&dest_color) == std::mem::discriminant(&template) {
        return dest_color;
    }
    let xyz = to_xyz65(dest_color);
    crate::gamut::clamp::from_xyz65_in_mode_of(xyz, template)
}

fn clamp_rgb_channels(c: Rgb) -> Rgb {
    Rgb {
        // culori's `fixup_rgb`: `Math.max(0, Math.min(c.r !== undefined ? c.r
        // : 0, 1))`. A missing channel becomes `0`. Our typed struct can
        // carry NaN through the conversion stack; treat NaN as absent and
        // map it to `0` to match.
        r: clamp01(c.r),
        g: clamp01(c.g),
        b: clamp01(c.b),
        alpha: c.alpha,
    }
}

fn clamp01(v: f64) -> f64 {
    if v.is_nan() {
        0.0
    } else {
        v.clamp(0.0, 1.0)
    }
}

/// Convert an `Rgb` back to whatever mode `template` is in. We need the
/// source mode (not the source value), so the caller passes a representative
/// `Color` of that mode.
fn convert_rgb_back_to_source_mode(rgb: Rgb, template: Color) -> Color {
    match template {
        Color::Rgb(_) => Color::Rgb(rgb),
        Color::LinearRgb(_) => Color::LinearRgb(LinearRgb::from(rgb)),
        Color::Hsl(_) => Color::Hsl(Hsl::from(rgb)),
        Color::Hsv(_) => Color::Hsv(Hsv::from(rgb)),
        Color::Hwb(_) => Color::Hwb(Hwb::from(Hsv::from(rgb))),
        Color::Lab(_) => Color::Lab(rgb.into()),
        Color::Lab65(_) => Color::Lab65(rgb.into()),
        Color::Lch(_) => Color::Lch(rgb.into()),
        Color::Lch65(_) => Color::Lch65(rgb.into()),
        Color::Oklab(_) => Color::Oklab(rgb.into()),
        Color::Oklch(_) => Color::Oklch(rgb.into()),
        Color::Xyz50(_) => Color::Xyz50(crate::convert(rgb)),
        Color::Xyz65(_) => Color::Xyz65(crate::convert(rgb)),
        Color::P3(_) => Color::P3(crate::convert(rgb)),
        Color::Rec2020(_) => Color::Rec2020(crate::convert(rgb)),
        Color::A98(_) => Color::A98(crate::convert(rgb)),
        Color::ProphotoRgb(_) => Color::ProphotoRgb(crate::convert(rgb)),
        Color::Cubehelix(_) => Color::Cubehelix(rgb.into()),
        Color::Dlab(_) => Color::Dlab(crate::convert(rgb)),
        Color::Dlch(_) => Color::Dlch(crate::convert(rgb)),
        Color::Jab(_) => Color::Jab(crate::convert(rgb)),
        Color::Jch(_) => Color::Jch(crate::convert(rgb)),
        Color::Yiq(_) => Color::Yiq(rgb.into()),
        Color::Hsi(_) => Color::Hsi(rgb.into()),
        Color::Hsluv(_) => Color::Hsluv(rgb.into()),
        Color::Hpluv(_) => Color::Hpluv(rgb.into()),
        Color::Okhsl(_) => Color::Okhsl(rgb.into()),
        Color::Okhsv(_) => Color::Okhsv(rgb.into()),
        Color::Itp(_) => Color::Itp(crate::convert(rgb)),
        Color::Xyb(_) => Color::Xyb(rgb.into()),
        Color::Luv(_) => Color::Luv(rgb.into()),
        Color::Lchuv(_) => Color::Lchuv(rgb.into()),
        Color::Prismatic(_) => Color::Prismatic(rgb.into()),
    }
}

/// Clamp the chroma of `color` until the result fits inside the sRGB gamut.
///
/// Mirrors culori's `clampChroma(color, mode)` with `rgbGamut = 'rgb'` (the
/// only value culori uses internally). `mode` is the LCh-like space used
/// for the bisection; pass `"lch"` for CIELCh or `"oklch"` for OkLCh.
///
/// When the input is already displayable, it is returned unchanged. When
/// even chroma = 0 is not displayable (a degenerate L outside `[0, 1]` /
/// `[0, 100]` for OkLCh / Lch) the function falls back to per-channel sRGB
/// clipping, matching culori.
///
/// The result is returned in the source mode of `color`.
pub fn clamp_chroma(color: Color, mode: &str) -> Color {
    if in_gamut(&color, "rgb") {
        return color;
    }

    // Bisect in `mode`. culori limits this to LCh-like spaces; we do the
    // same via the explicit match. Other mode strings are an error.
    let (start_l, start_c, start_h, alpha, range_max) = match mode {
        "lch" => {
            let lch: Lch = match color {
                Color::Lch(x) => x,
                _ => crate::convert::<crate::spaces::Xyz65, Lch>(to_xyz65(color)),
            };
            (lch.l, lch.c, lch.h, lch.alpha, 150.0_f64)
        }
        "oklch" => {
            let oklch: Oklch = match color {
                Color::Oklch(x) => x,
                _ => {
                    use crate::traits::ColorSpace;
                    Oklch::from(crate::spaces::Oklab::from_xyz65(to_xyz65(color)))
                }
            };
            (oklch.l, oklch.c, oklch.h, oklch.alpha, 0.4_f64)
        }
        other => panic!("clamp_chroma: mode must be 'lch' or 'oklch', got '{other}'"),
    };

    // culori's `resolution = (range_max - range_min) / 2^13`. Both lch and
    // oklch have `range_min = 0`, so `resolution = range_max / 8192`.
    const ITER_DENOM: f64 = 8192.0;
    let resolution = range_max / ITER_DENOM;

    // Try chroma = 0 first. If even that is out of gamut, fall back to
    // per-channel rgb clipping of the chroma-zero color.
    let mut clamped = make_polar(mode, start_l, 0.0, start_h, alpha);
    if !in_gamut(&clamped, "rgb") {
        let rgb = clamp_rgb_channels(color_to_rgb(clamped));
        return convert_rgb_back_to_source_mode(rgb, color);
    }

    // Bisect: `start` is the largest chroma known to be in gamut, `end` is
    // the largest chroma known to be out.
    let mut start = 0.0;
    let mut end = if start_c.is_nan() { 0.0 } else { start_c };
    let mut last_good_c = 0.0;
    while end - start > resolution {
        let mid = start + (end - start) * 0.5;
        clamped = make_polar(mode, start_l, mid, start_h, alpha);
        if in_gamut(&clamped, "rgb") {
            last_good_c = mid;
            start = mid;
        } else {
            end = mid;
        }
    }

    // After the loop, `clamped` carries the last tested chroma. If that
    // chroma is in gamut, return as-is; otherwise back off to the last
    // known-good chroma. Mirrors culori's final ternary.
    let final_color = if in_gamut(&clamped, "rgb") {
        clamped
    } else {
        make_polar(mode, start_l, last_good_c, start_h, alpha)
    };

    // Convert the result back to the source mode.
    convert_polar_to_source_mode(final_color, color)
}

fn make_polar(mode: &str, l: f64, c: f64, h: f64, alpha: Option<f64>) -> Color {
    match mode {
        "lch" => Color::Lch(Lch { l, c, h, alpha }),
        "oklch" => Color::Oklch(Oklch { l, c, h, alpha }),
        _ => unreachable!(),
    }
}

fn convert_polar_to_source_mode(polar: Color, template: Color) -> Color {
    // Same source mode → return as-is.
    if std::mem::discriminant(&polar) == std::mem::discriminant(&template) {
        return polar;
    }
    // Otherwise fall through `XYZ65`. For the `Lab`/`Oklab` ↔ `Lch`/`Oklch`
    // sub-cases we could shave a step, but every other case routes through
    // the hub anyway.
    let xyz = to_xyz65(polar);
    from_xyz65_in_mode_of(xyz, template)
}

pub(crate) fn to_xyz65(c: Color) -> crate::spaces::Xyz65 {
    use crate::traits::ColorSpace;
    match c {
        Color::Rgb(x) => x.to_xyz65(),
        Color::LinearRgb(x) => x.to_xyz65(),
        Color::Hsl(x) => x.to_xyz65(),
        Color::Hsv(x) => x.to_xyz65(),
        Color::Hwb(x) => x.to_xyz65(),
        Color::Lab(x) => x.to_xyz65(),
        Color::Lab65(x) => x.to_xyz65(),
        Color::Lch(x) => x.to_xyz65(),
        Color::Lch65(x) => x.to_xyz65(),
        Color::Oklab(x) => x.to_xyz65(),
        Color::Oklch(x) => x.to_xyz65(),
        Color::Xyz50(x) => x.to_xyz65(),
        Color::Xyz65(x) => x,
        Color::P3(x) => x.to_xyz65(),
        Color::Rec2020(x) => x.to_xyz65(),
        Color::A98(x) => x.to_xyz65(),
        Color::ProphotoRgb(x) => x.to_xyz65(),
        Color::Cubehelix(x) => x.to_xyz65(),
        Color::Dlab(x) => x.to_xyz65(),
        Color::Dlch(x) => x.to_xyz65(),
        Color::Jab(x) => x.to_xyz65(),
        Color::Jch(x) => x.to_xyz65(),
        Color::Yiq(x) => x.to_xyz65(),
        Color::Hsi(x) => x.to_xyz65(),
        Color::Hsluv(x) => x.to_xyz65(),
        Color::Hpluv(x) => x.to_xyz65(),
        Color::Okhsl(x) => x.to_xyz65(),
        Color::Okhsv(x) => x.to_xyz65(),
        Color::Itp(x) => x.to_xyz65(),
        Color::Xyb(x) => x.to_xyz65(),
        Color::Luv(x) => x.to_xyz65(),
        Color::Lchuv(x) => x.to_xyz65(),
        Color::Prismatic(x) => x.to_xyz65(),
    }
}

fn from_xyz65_in_mode_of(xyz: crate::spaces::Xyz65, template: Color) -> Color {
    use crate::traits::ColorSpace;
    match template {
        Color::Rgb(_) => Color::Rgb(Rgb::from_xyz65(xyz)),
        Color::LinearRgb(_) => Color::LinearRgb(LinearRgb::from_xyz65(xyz)),
        Color::Hsl(_) => Color::Hsl(Hsl::from_xyz65(xyz)),
        Color::Hsv(_) => Color::Hsv(Hsv::from_xyz65(xyz)),
        Color::Hwb(_) => Color::Hwb(Hwb::from_xyz65(xyz)),
        Color::Lab(_) => Color::Lab(crate::spaces::Lab::from_xyz65(xyz)),
        Color::Lab65(_) => Color::Lab65(crate::spaces::Lab65::from_xyz65(xyz)),
        Color::Lch(_) => Color::Lch(Lch::from_xyz65(xyz)),
        Color::Lch65(_) => Color::Lch65(crate::spaces::Lch65::from_xyz65(xyz)),
        Color::Oklab(_) => Color::Oklab(crate::spaces::Oklab::from_xyz65(xyz)),
        Color::Oklch(_) => Color::Oklch(Oklch::from_xyz65(xyz)),
        Color::Xyz50(_) => Color::Xyz50(crate::spaces::Xyz50::from_xyz65(xyz)),
        Color::Xyz65(_) => Color::Xyz65(xyz),
        Color::P3(_) => Color::P3(crate::spaces::P3::from_xyz65(xyz)),
        Color::Rec2020(_) => Color::Rec2020(crate::spaces::Rec2020::from_xyz65(xyz)),
        Color::A98(_) => Color::A98(crate::spaces::A98::from_xyz65(xyz)),
        Color::ProphotoRgb(_) => Color::ProphotoRgb(crate::spaces::ProphotoRgb::from_xyz65(xyz)),
        Color::Cubehelix(_) => Color::Cubehelix(crate::spaces::Cubehelix::from_xyz65(xyz)),
        Color::Dlab(_) => Color::Dlab(crate::spaces::Dlab::from_xyz65(xyz)),
        Color::Dlch(_) => Color::Dlch(crate::spaces::Dlch::from_xyz65(xyz)),
        Color::Jab(_) => Color::Jab(crate::spaces::Jab::from_xyz65(xyz)),
        Color::Jch(_) => Color::Jch(crate::spaces::Jch::from_xyz65(xyz)),
        Color::Yiq(_) => Color::Yiq(crate::spaces::Yiq::from_xyz65(xyz)),
        Color::Hsi(_) => Color::Hsi(crate::spaces::Hsi::from_xyz65(xyz)),
        Color::Hsluv(_) => Color::Hsluv(crate::spaces::Hsluv::from_xyz65(xyz)),
        Color::Hpluv(_) => Color::Hpluv(crate::spaces::Hpluv::from_xyz65(xyz)),
        Color::Okhsl(_) => Color::Okhsl(crate::spaces::Okhsl::from_xyz65(xyz)),
        Color::Okhsv(_) => Color::Okhsv(crate::spaces::Okhsv::from_xyz65(xyz)),
        Color::Itp(_) => Color::Itp(crate::spaces::Itp::from_xyz65(xyz)),
        Color::Xyb(_) => Color::Xyb(crate::spaces::Xyb::from_xyz65(xyz)),
        Color::Luv(_) => Color::Luv(crate::spaces::Luv::from_xyz65(xyz)),
        Color::Lchuv(_) => Color::Lchuv(crate::spaces::Lchuv::from_xyz65(xyz)),
        Color::Prismatic(_) => Color::Prismatic(crate::spaces::Prismatic::from_xyz65(xyz)),
    }
}