stet_graphics/

color.rs

// stet - A PostScript Interpreter
// Copyright (c) 2026 Scott Bowman
// SPDX-License-Identifier: Apache-2.0 OR MIT

//! Color types and CIE color space parameters.

/// Line cap style.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum LineCap {
    Butt = 0,
    Round = 1,
    Square = 2,
}

impl LineCap {
    pub fn from_i32(v: i32) -> Option<Self> {
        match v {
            0 => Some(Self::Butt),
            1 => Some(Self::Round),
            2 => Some(Self::Square),
            _ => None,
        }
    }
}

/// Line join style.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum LineJoin {
    Miter = 0,
    Round = 1,
    Bevel = 2,
}

impl LineJoin {
    pub fn from_i32(v: i32) -> Option<Self> {
        match v {
            0 => Some(Self::Miter),
            1 => Some(Self::Round),
            2 => Some(Self::Bevel),
            _ => None,
        }
    }
}

/// Fill rule for path filling.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum FillRule {
    NonZeroWinding,
    EvenOdd,
}

/// Dash pattern for stroked paths.
#[derive(Clone, Debug)]
pub struct DashPattern {
    pub array: Vec<f64>,
    pub offset: f64,
}

impl DashPattern {
    pub fn solid() -> Self {
        Self {
            array: Vec::new(),
            offset: 0.0,
        }
    }
}

impl Default for DashPattern {
    fn default() -> Self {
        Self::solid()
    }
}

/// Device color in RGB (internal representation) with optional native CMYK.
#[derive(Clone, Debug)]
pub struct DeviceColor {
    pub r: f64,
    pub g: f64,
    pub b: f64,
    /// Native CMYK components for lossless roundtrip when color space is CMYK.
    /// For DeviceN/Separation paints this is the *full* alt-CMYK tint transform
    /// (process + spot contributions combined).
    pub native_cmyk: Option<(f64, f64, f64, f64)>,
    /// Process-colorant-only CMYK contribution. Populated by DeviceN/Separation
    /// paints so the overprint tracker can record only what actually lands on
    /// process plates (C/M/Y/K), leaving any spot colorant's alt-CMYK out of
    /// the process buffer. `None` means "use `native_cmyk` as the process
    /// contribution" (pure DeviceCMYK / DeviceGray / DeviceRGB).
    pub process_cmyk: Option<(f64, f64, f64, f64)>,
}

impl DeviceColor {
    pub fn from_gray(gray: f64) -> Self {
        Self {
            r: gray,
            g: gray,
            b: gray,
            native_cmyk: None,
            process_cmyk: None,
        }
    }

    pub fn from_rgb(r: f64, g: f64, b: f64) -> Self {
        Self {
            r,
            g,
            b,
            native_cmyk: None,
            process_cmyk: None,
        }
    }

    pub fn from_cmyk(c: f64, m: f64, y: f64, k: f64) -> Self {
        Self {
            r: 1.0 - (c + k).min(1.0),
            g: 1.0 - (m + k).min(1.0),
            b: 1.0 - (y + k).min(1.0),
            native_cmyk: Some((c, m, y, k)),
            process_cmyk: None,
        }
    }

    /// Create from CMYK, converting through ICC profile if available.
    /// Falls back to PLRM formula when ICC is unavailable.
    pub fn from_cmyk_icc(c: f64, m: f64, y: f64, k: f64, icc: &mut crate::icc::IccCache) -> Self {
        if let Some((r, g, b)) = icc.convert_cmyk(c, m, y, k) {
            Self {
                r,
                g,
                b,
                native_cmyk: Some((c, m, y, k)),
                process_cmyk: None,
            }
        } else {
            Self::from_cmyk(c, m, y, k)
        }
    }

    pub fn from_hsb(h: f64, s: f64, b: f64) -> Self {
        if s == 0.0 {
            return Self::from_gray(b);
        }
        if b == 0.0 {
            return Self::from_gray(0.0);
        }

        let mut hue = h * 6.0;
        if hue >= 6.0 {
            hue = 0.0;
        }

        let sector = hue as i32;
        let frac = hue - sector as f64;

        let p = b * (1.0 - s);
        let q = b * (1.0 - s * frac);
        let t = b * (1.0 - s * (1.0 - frac));

        let (r, g, bl) = match sector {
            0 => (b, t, p),
            1 => (q, b, p),
            2 => (p, b, t),
            3 => (p, q, b),
            4 => (t, p, b),
            _ => (b, p, q),
        };

        Self {
            r,
            g,
            b: bl,
            native_cmyk: None,
            process_cmyk: None,
        }
    }

    /// Convert to gray using NTSC luma.
    pub fn to_gray(&self) -> f64 {
        0.3 * self.r + 0.59 * self.g + 0.11 * self.b
    }

    /// Convert to CMYK (uses native CMYK if available for lossless roundtrip).
    pub fn to_cmyk(&self) -> (f64, f64, f64, f64) {
        if let Some(cmyk) = self.native_cmyk {
            return cmyk;
        }
        let c = 1.0 - self.r;
        let m = 1.0 - self.g;
        let y = 1.0 - self.b;
        let k = c.min(m).min(y);
        (
            (c - k).clamp(0.0, 1.0),
            (m - k).clamp(0.0, 1.0),
            (y - k).clamp(0.0, 1.0),
            k.clamp(0.0, 1.0),
        )
    }

    /// Convert to HSB.
    pub fn to_hsb(&self) -> (f64, f64, f64) {
        let max_val = self.r.max(self.g).max(self.b);
        let min_val = self.r.min(self.g).min(self.b);
        let diff = max_val - min_val;

        let brightness = max_val;
        let saturation = if max_val == 0.0 { 0.0 } else { diff / max_val };

        let hue = if diff == 0.0 {
            0.0
        } else if max_val == self.r {
            let mut h = (self.g - self.b) / diff;
            if h < 0.0 {
                h += 6.0;
            }
            h / 6.0
        } else if max_val == self.g {
            ((self.b - self.r) / diff + 2.0) / 6.0
        } else {
            ((self.r - self.g) / diff + 4.0) / 6.0
        };

        (hue, saturation, brightness)
    }

    /// Black (default color).
    pub fn black() -> Self {
        Self {
            r: 0.0,
            g: 0.0,
            b: 0.0,
            native_cmyk: None,
            process_cmyk: None,
        }
    }

    /// Apply sRGB gamma companding (linear → gamma-corrected).
    fn srgb_gamma(u: f64) -> f64 {
        if u <= 0.0031308 {
            12.92 * u
        } else {
            1.055 * u.powf(1.0 / 2.4) - 0.055
        }
    }

    /// Convert CIE XYZ (D65-adapted) to sRGB.
    fn from_xyz(x: f64, y: f64, z: f64) -> Self {
        // IEC 61966-2-1 sRGB D65 XYZ → linear RGB matrix
        let lr = 3.2404542 * x + (-1.5371385) * y + (-0.4985314) * z;
        let lg = (-0.9692660) * x + 1.8760108 * y + 0.0415560 * z;
        let lb = 0.0556434 * x + (-0.2040259) * y + 1.0572252 * z;

        Self {
            r: Self::srgb_gamma(lr.max(0.0)).clamp(0.0, 1.0),
            g: Self::srgb_gamma(lg.max(0.0)).clamp(0.0, 1.0),
            b: Self::srgb_gamma(lb.max(0.0)).clamp(0.0, 1.0),
            native_cmyk: None,
            process_cmyk: None,
        }
    }

    /// Bradford chromatic adaptation: adapt XYZ from source white point to D65.
    fn adapt_xyz_to_d65(x: f64, y: f64, z: f64, src_wp: &[f64; 3]) -> [f64; 3] {
        // D65 white point (sRGB standard illuminant)
        const D65: [f64; 3] = [0.95047, 1.0, 1.08883];

        // Skip adaptation if source is already D65
        if (src_wp[0] - D65[0]).abs() < 1e-3
            && (src_wp[1] - D65[1]).abs() < 1e-3
            && (src_wp[2] - D65[2]).abs() < 1e-3
        {
            return [x, y, z];
        }

        // Bradford matrix (XYZ → LMS cone space), column-major
        const M: [f64; 9] = [
            0.8951, -0.7502, 0.0389, 0.2664, 1.7135, -0.0685, -0.1614, 0.0367, 1.0296,
        ];
        // Inverse Bradford matrix (LMS → XYZ), column-major
        const M_INV: [f64; 9] = [
            0.9869929, 0.4323053, -0.0085287, -0.1470543, 0.5183603, 0.0400428, 0.1599627,
            0.0492912, 0.9684867,
        ];

        // Convert source and D65 white points to LMS
        let lms_src = Self::apply_matrix_3x3(&M, src_wp);
        let lms_d65 = Self::apply_matrix_3x3(&M, &D65);

        // Diagonal scaling in LMS space
        let s0 = if lms_src[0].abs() > 1e-10 {
            lms_d65[0] / lms_src[0]
        } else {
            1.0
        };
        let s1 = if lms_src[1].abs() > 1e-10 {
            lms_d65[1] / lms_src[1]
        } else {
            1.0
        };
        let s2 = if lms_src[2].abs() > 1e-10 {
            lms_d65[2] / lms_src[2]
        } else {
            1.0
        };

        // Adapt: M_inv × diag(s) × M × [x, y, z]
        let lms = Self::apply_matrix_3x3(&M, &[x, y, z]);
        let scaled = [lms[0] * s0, lms[1] * s1, lms[2] * s2];
        Self::apply_matrix_3x3(&M_INV, &scaled)
    }

    /// Apply a column-major 3×3 matrix to a 3-element vector.
    fn apply_matrix_3x3(mat: &[f64; 9], v: &[f64; 3]) -> [f64; 3] {
        [
            mat[0] * v[0] + mat[3] * v[1] + mat[6] * v[2],
            mat[1] * v[0] + mat[4] * v[1] + mat[7] * v[2],
            mat[2] * v[0] + mat[5] * v[1] + mat[8] * v[2],
        ]
    }

    /// Linear interpolation in a pre-evaluated decode table.
    fn decode_lookup(table: &[f64], value: f64) -> f64 {
        let n = table.len();
        if n < 2 {
            return table.first().copied().unwrap_or(value);
        }
        let idx = value * (n - 1) as f64;
        let i0 = (idx as usize).min(n - 2);
        let frac = idx - i0 as f64;
        table[i0] + (table[i0 + 1] - table[i0]) * frac
    }

    /// Convert CIE L\*a\*b\* to sRGB.
    ///
    /// PDF Lab color spaces specify a white point, but Lab is perceptually
    /// uniform — the same (L\*, a\*, b\*) coordinates represent the same
    /// perceived color regardless of the declared white point.  We convert
    /// directly through D65 (the sRGB reference illuminant), which makes
    /// the specified white point irrelevant and avoids Bradford adaptation
    /// errors for extreme/non-physical white points.
    ///
    /// `range` is the a\*/b\* clamp range: [a_min, a_max, b_min, b_max].
    pub fn from_lab(l_star: f64, a_star: f64, b_star: f64, range: &[f64; 4]) -> Self {
        // D65 white point (sRGB reference illuminant)
        const D65: [f64; 3] = [0.95047, 1.0, 1.08883];

        let l_star = l_star.clamp(0.0, 100.0);
        let a_star = a_star.clamp(range[0], range[1]);
        let b_star = b_star.clamp(range[2], range[3]);

        let fy = (l_star + 16.0) / 116.0;
        let fx = a_star / 500.0 + fy;
        let fz = fy - b_star / 200.0;

        let x = D65[0] * Self::lab_f_inv(fx);
        let y = D65[1] * Self::lab_f_inv(fy);
        let z = D65[2] * Self::lab_f_inv(fz);

        Self::from_xyz(x, y, z)
    }

    fn lab_f_inv(t: f64) -> f64 {
        if t > 6.0 / 29.0 {
            t * t * t
        } else {
            3.0 * (6.0 / 29.0) * (6.0 / 29.0) * (t - 4.0 / 29.0)
        }
    }

    /// Convert CIEBasedABC color to sRGB.
    pub fn from_cie_abc(a: f64, b: f64, c: f64, params: &CieAbcParams) -> Self {
        let mut a = a.clamp(params.range_abc[0], params.range_abc[1]);
        let mut b = b.clamp(params.range_abc[2], params.range_abc[3]);
        let mut c = c.clamp(params.range_abc[4], params.range_abc[5]);

        if let Some(ref tables) = params.decode_abc {
            let ra = params.range_abc[1] - params.range_abc[0];
            let rb = params.range_abc[3] - params.range_abc[2];
            let rc = params.range_abc[5] - params.range_abc[4];
            let na = if ra > 0.0 {
                (a - params.range_abc[0]) / ra
            } else {
                0.0
            };
            let nb = if rb > 0.0 {
                (b - params.range_abc[2]) / rb
            } else {
                0.0
            };
            let nc = if rc > 0.0 {
                (c - params.range_abc[4]) / rc
            } else {
                0.0
            };
            a = Self::decode_lookup(&tables[0], na);
            b = Self::decode_lookup(&tables[1], nb);
            c = Self::decode_lookup(&tables[2], nc);
        }

        let lmn = Self::apply_matrix_3x3(&params.matrix_abc, &[a, b, c]);

        let mut l = lmn[0].clamp(params.range_lmn[0], params.range_lmn[1]);
        let mut m = lmn[1].clamp(params.range_lmn[2], params.range_lmn[3]);
        let mut n = lmn[2].clamp(params.range_lmn[4], params.range_lmn[5]);

        if let Some(ref tables) = params.decode_lmn {
            let rl = params.range_lmn[1] - params.range_lmn[0];
            let rm = params.range_lmn[3] - params.range_lmn[2];
            let rn = params.range_lmn[5] - params.range_lmn[4];
            let nl = if rl > 0.0 {
                (l - params.range_lmn[0]) / rl
            } else {
                0.0
            };
            let nm = if rm > 0.0 {
                (m - params.range_lmn[2]) / rm
            } else {
                0.0
            };
            let nn = if rn > 0.0 {
                (n - params.range_lmn[4]) / rn
            } else {
                0.0
            };
            l = Self::decode_lookup(&tables[0], nl);
            m = Self::decode_lookup(&tables[1], nm);
            n = Self::decode_lookup(&tables[2], nn);
        }

        let xyz = Self::apply_matrix_3x3(&params.matrix_lmn, &[l, m, n]);

        // Chromatic adaptation from source white point to D65
        let xyz = Self::adapt_xyz_to_d65(xyz[0], xyz[1], xyz[2], &params.white_point);
        Self::from_xyz(xyz[0], xyz[1], xyz[2])
    }

    /// Convert CIEBasedA color to sRGB.
    pub fn from_cie_a(a: f64, params: &CieAParams) -> Self {
        let mut a = a.clamp(params.range_a[0], params.range_a[1]);

        if let Some(ref table) = params.decode_a {
            let ra = params.range_a[1] - params.range_a[0];
            let na = if ra > 0.0 {
                (a - params.range_a[0]) / ra
            } else {
                0.0
            };
            a = Self::decode_lookup(table, na);
        }

        let lmn = [
            params.matrix_a[0] * a,
            params.matrix_a[1] * a,
            params.matrix_a[2] * a,
        ];

        let mut l = lmn[0].clamp(params.range_lmn[0], params.range_lmn[1]);
        let mut m = lmn[1].clamp(params.range_lmn[2], params.range_lmn[3]);
        let mut n = lmn[2].clamp(params.range_lmn[4], params.range_lmn[5]);

        if let Some(ref tables) = params.decode_lmn {
            let rl = params.range_lmn[1] - params.range_lmn[0];
            let rm = params.range_lmn[3] - params.range_lmn[2];
            let rn = params.range_lmn[5] - params.range_lmn[4];
            let nl = if rl > 0.0 {
                (l - params.range_lmn[0]) / rl
            } else {
                0.0
            };
            let nm = if rm > 0.0 {
                (m - params.range_lmn[2]) / rm
            } else {
                0.0
            };
            let nn = if rn > 0.0 {
                (n - params.range_lmn[4]) / rn
            } else {
                0.0
            };
            l = Self::decode_lookup(&tables[0], nl);
            m = Self::decode_lookup(&tables[1], nm);
            n = Self::decode_lookup(&tables[2], nn);
        }

        let xyz = Self::apply_matrix_3x3(&params.matrix_lmn, &[l, m, n]);

        // Chromatic adaptation from source white point to D65
        let xyz = Self::adapt_xyz_to_d65(xyz[0], xyz[1], xyz[2], &params.white_point);
        Self::from_xyz(xyz[0], xyz[1], xyz[2])
    }

    /// Convert CIEBasedDEF color to sRGB via pre-converted trilinear interpolation table.
    pub fn from_cie_def(d: f64, e: f64, f: f64, params: &CieDefParams) -> Self {
        let (m1, m2, m3) = (params.m1, params.m2, params.m3);
        if m1 < 2 || m2 < 2 || m3 < 2 {
            return Self::from_gray(0.0);
        }

        let d_range = params.range_def[1] - params.range_def[0];
        let e_range = params.range_def[3] - params.range_def[2];
        let f_range = params.range_def[5] - params.range_def[4];

        let di = if d_range > 0.0 {
            ((d - params.range_def[0]) / d_range * (m1 - 1) as f64).clamp(0.0, (m1 - 1) as f64)
        } else {
            0.0
        };
        let ei = if e_range > 0.0 {
            ((e - params.range_def[2]) / e_range * (m2 - 1) as f64).clamp(0.0, (m2 - 1) as f64)
        } else {
            0.0
        };
        let fi = if f_range > 0.0 {
            ((f - params.range_def[4]) / f_range * (m3 - 1) as f64).clamp(0.0, (m3 - 1) as f64)
        } else {
            0.0
        };

        let di0 = (di as usize).min(m1 - 2);
        let ei0 = (ei as usize).min(m2 - 2);
        let fi0 = (fi as usize).min(m3 - 2);
        let di1 = di0 + 1;
        let ei1 = ei0 + 1;
        let fi1 = fi0 + 1;
        let dd = di - di0 as f64;
        let de = ei - ei0 as f64;
        let df = fi - fi0 as f64;

        let stride_e = m3;
        let stride_d = m2 * m3;

        let mut abc = [0.0f64; 3];
        for (ch, table) in [&params.a_table, &params.b_table, &params.c_table]
            .iter()
            .enumerate()
        {
            let c000 = table[di0 * stride_d + ei0 * stride_e + fi0];
            let c001 = table[di0 * stride_d + ei0 * stride_e + fi1];
            let c010 = table[di0 * stride_d + ei1 * stride_e + fi0];
            let c011 = table[di0 * stride_d + ei1 * stride_e + fi1];
            let c100 = table[di1 * stride_d + ei0 * stride_e + fi0];
            let c101 = table[di1 * stride_d + ei0 * stride_e + fi1];
            let c110 = table[di1 * stride_d + ei1 * stride_e + fi0];
            let c111 = table[di1 * stride_d + ei1 * stride_e + fi1];

            let c00 = c000 * (1.0 - df) + c001 * df;
            let c01 = c010 * (1.0 - df) + c011 * df;
            let c10 = c100 * (1.0 - df) + c101 * df;
            let c11 = c110 * (1.0 - df) + c111 * df;

            let c0 = c00 * (1.0 - de) + c01 * de;
            let c1 = c10 * (1.0 - de) + c11 * de;

            abc[ch] = c0 * (1.0 - dd) + c1 * dd;
        }

        Self::from_cie_abc(abc[0], abc[1], abc[2], &params.abc_params)
    }

    /// Convert CIEBasedDEFG color to sRGB via pre-converted nearest-neighbor 4D table.
    pub fn from_cie_defg(d: f64, e: f64, f: f64, g: f64, params: &CieDefgParams) -> Self {
        let (m1, m2, m3, m4) = (params.m1, params.m2, params.m3, params.m4);
        if m1 == 0 || m2 == 0 || m3 == 0 || m4 == 0 {
            return Self::from_gray(0.0);
        }

        let d_range = params.range_defg[1] - params.range_defg[0];
        let e_range = params.range_defg[3] - params.range_defg[2];
        let f_range = params.range_defg[5] - params.range_defg[4];
        let g_range = params.range_defg[7] - params.range_defg[6];

        let di = if d_range > 0.0 {
            ((d - params.range_defg[0]) / d_range * (m1 - 1) as f64 + 0.5) as usize
        } else {
            0
        }
        .min(m1 - 1);
        let ei = if e_range > 0.0 {
            ((e - params.range_defg[2]) / e_range * (m2 - 1) as f64 + 0.5) as usize
        } else {
            0
        }
        .min(m2 - 1);
        let fi = if f_range > 0.0 {
            ((f - params.range_defg[4]) / f_range * (m3 - 1) as f64 + 0.5) as usize
        } else {
            0
        }
        .min(m3 - 1);
        let gi = if g_range > 0.0 {
            ((g - params.range_defg[6]) / g_range * (m4 - 1) as f64 + 0.5) as usize
        } else {
            0
        }
        .min(m4 - 1);

        let idx = di * m2 * m3 * m4 + ei * m3 * m4 + fi * m4 + gi;
        if idx >= params.a_table.len() {
            return Self::from_gray(0.0);
        }

        Self::from_cie_abc(
            params.a_table[idx],
            params.b_table[idx],
            params.c_table[idx],
            &params.abc_params,
        )
    }
}

/// Extracted parameters for CIEBasedABC color conversion.
#[derive(Clone, Debug)]
pub struct CieAbcParams {
    pub range_abc: [f64; 6],
    pub decode_abc: Option<[Vec<f64>; 3]>,
    pub matrix_abc: [f64; 9],
    pub range_lmn: [f64; 6],
    pub decode_lmn: Option<[Vec<f64>; 3]>,
    pub matrix_lmn: [f64; 9],
    pub white_point: [f64; 3],
}

impl Default for CieAbcParams {
    fn default() -> Self {
        Self {
            range_abc: [0.0, 1.0, 0.0, 1.0, 0.0, 1.0],
            decode_abc: None,
            matrix_abc: [1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0],
            range_lmn: [0.0, 1.0, 0.0, 1.0, 0.0, 1.0],
            decode_lmn: None,
            matrix_lmn: [1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0],
            white_point: [0.9505, 1.0, 1.089],
        }
    }
}

/// Extracted parameters for CIEBasedA color conversion.
#[derive(Clone, Debug)]
pub struct CieAParams {
    pub range_a: [f64; 2],
    pub decode_a: Option<Vec<f64>>,
    pub matrix_a: [f64; 3],
    pub range_lmn: [f64; 6],
    pub decode_lmn: Option<[Vec<f64>; 3]>,
    pub matrix_lmn: [f64; 9],
    pub white_point: [f64; 3],
}

impl Default for CieAParams {
    fn default() -> Self {
        Self {
            range_a: [0.0, 1.0],
            decode_a: None,
            matrix_a: [1.0, 1.0, 1.0],
            range_lmn: [0.0, 1.0, 0.0, 1.0, 0.0, 1.0],
            decode_lmn: None,
            matrix_lmn: [1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0],
            white_point: [0.9505, 1.0, 1.089],
        }
    }
}

/// Pre-converted parameters for CIEBasedDEF color space (3D table → RGB).
#[derive(Clone, Debug)]
pub struct CieDefParams {
    pub range_def: [f64; 6],
    pub m1: usize,
    pub m2: usize,
    pub m3: usize,
    pub a_table: Vec<f64>,
    pub b_table: Vec<f64>,
    pub c_table: Vec<f64>,
    pub abc_params: CieAbcParams,
}

/// Parameters for CIEBasedDEFG color space (4D table → ABC → CIE pipeline).
#[derive(Clone, Debug)]
pub struct CieDefgParams {
    pub range_defg: [f64; 8],
    pub m1: usize,
    pub m2: usize,
    pub m3: usize,
    pub m4: usize,
    pub a_table: Vec<f64>,
    pub b_table: Vec<f64>,
    pub c_table: Vec<f64>,
    pub abc_params: CieAbcParams,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_color_from_gray() {
        let c = DeviceColor::from_gray(0.5);
        assert!((c.r - 0.5).abs() < 1e-10);
        assert!((c.g - 0.5).abs() < 1e-10);
        assert!((c.b - 0.5).abs() < 1e-10);
    }

    #[test]
    fn test_color_from_cmyk() {
        let c = DeviceColor::from_cmyk(1.0, 0.0, 0.0, 0.0);
        assert!((c.r - 0.0).abs() < 1e-10);
        assert!((c.g - 1.0).abs() < 1e-10);
        assert!((c.b - 1.0).abs() < 1e-10);
    }

    #[test]
    fn test_color_from_hsb() {
        let c = DeviceColor::from_hsb(0.0, 1.0, 1.0);
        assert!((c.r - 1.0).abs() < 1e-10);
        assert!((c.g - 0.0).abs() < 1e-10);
        assert!((c.b - 0.0).abs() < 1e-10);

        let c = DeviceColor::from_hsb(1.0 / 3.0, 1.0, 1.0);
        assert!((c.r - 0.0).abs() < 1e-10);
        assert!((c.g - 1.0).abs() < 1e-10);
        assert!((c.b - 0.0).abs() < 1e-10);
    }

    #[test]
    fn test_color_gray_roundtrip() {
        let c = DeviceColor::from_gray(0.5);
        let gray = c.to_gray();
        assert!((gray - 0.5).abs() < 1e-10);
    }

    #[test]
    fn test_color_hsb_roundtrip() {
        let c = DeviceColor::from_hsb(0.6, 0.8, 0.9);
        let (h, s, b) = c.to_hsb();
        assert!((h - 0.6).abs() < 0.01);
        assert!((s - 0.8).abs() < 0.01);
        assert!((b - 0.9).abs() < 0.01);
    }

    #[test]
    fn test_linecap_from_i32() {
        assert_eq!(LineCap::from_i32(0), Some(LineCap::Butt));
        assert_eq!(LineCap::from_i32(1), Some(LineCap::Round));
        assert_eq!(LineCap::from_i32(2), Some(LineCap::Square));
        assert_eq!(LineCap::from_i32(3), None);
    }

    #[test]
    fn test_linejoin_from_i32() {
        assert_eq!(LineJoin::from_i32(0), Some(LineJoin::Miter));
        assert_eq!(LineJoin::from_i32(1), Some(LineJoin::Round));
        assert_eq!(LineJoin::from_i32(2), Some(LineJoin::Bevel));
        assert_eq!(LineJoin::from_i32(3), None);
    }
}