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    use super::*;
    use std::convert::TryFrom;
    use std::str::FromStr;

    // To Lab /////////////////////////////////////////////////////////////////////
    impl From<LchValue> for LabValue {
        fn from(lch: LchValue) -> LabValue {
            LabValue {
                l: lch.l,
                a: lch.c * lch.h.to_radians().cos(),
                b: lch.c * lch.h.to_radians().sin(),
            }
        }
    }

    impl From<&LchValue> for LabValue {
        fn from(lch: &LchValue) -> LabValue {
            LabValue::from(*lch)
        }
    }

    impl From<&LabValue> for LabValue {
        fn from(lab: &LabValue) -> LabValue {
            *lab
        }
    }

    impl From<XyzValue> for LabValue {
        fn from(xyz: XyzValue) -> LabValue {
            let x = xyz_to_lab_map(xyz.x / 0.9642);
            let y = xyz_to_lab_map(xyz.y);
            let z = xyz_to_lab_map(xyz.z / 0.8251);

            LabValue {
                l: (116.0 * y) - 16.0,
                a: 500.0 * (x - y),
                b: 200.0 * (y - z),
            }
        }
    }

    impl From<&XyzValue> for LabValue {
        fn from(xyz: &XyzValue) -> LabValue {
            LabValue::from(*xyz)
        }
    }

    impl TryFrom<&[f32; 3]> for LabValue {
        type Error = ValueError;
        fn try_from(slice: &[f32; 3]) -> ValueResult<LabValue> {
            LabValue {
                l: slice[0],
                a: slice[1],
                b: slice[2]
            }.validate()
        }
    }

    impl TryFrom<(f32, f32, f32)> for LabValue {
        type Error = ValueError;
        fn try_from(tuple: (f32, f32, f32)) -> ValueResult<LabValue> {
            LabValue {
                l: tuple.0,
                a: tuple.1,
                b: tuple.2,
            }.validate()
        }
    }

    impl TryFrom<&(f32, f32, f32)> for LabValue {
        type Error = ValueError;
        fn try_from(tuple: &(f32, f32, f32)) -> ValueResult<LabValue> {
            LabValue {
                l: tuple.0,
                a: tuple.1,
                b: tuple.2,
            }.validate()
        }
    }

    // To Lch /////////////////////////////////////////////////////////////////////
    impl From<LabValue> for LchValue {
        fn from(lab: LabValue) -> LchValue {
            LchValue {
                l: lab.l,
                c: ( lab.a.powi(2) + lab.b.powi(2) ).sqrt(),
                h: get_h_prime(lab.a, lab.b),
            }
        }
    }

    impl From<&LabValue> for LchValue {
        fn from(lab: &LabValue) -> LchValue {
            LchValue::from(*lab)
        }
    }

    impl From<XyzValue> for LchValue {
        fn from(xyz: XyzValue) -> LchValue {
            LchValue::from(LabValue::from(xyz))
        }
    }

    impl From<&XyzValue> for LchValue {
        fn from(xyz: &XyzValue) -> LchValue {
            LchValue::from(*xyz)
        }
    }

    impl TryFrom<&[f32; 3]> for LchValue {
        type Error = ValueError;
        fn try_from(slice: &[f32; 3]) -> ValueResult<LchValue> {
            LchValue {
                l: slice[0],
                c: slice[1],
                h: slice[2]
            }.validate()
        }
    }

    impl TryFrom<(f32, f32, f32)> for LchValue {
        type Error = ValueError;
        fn try_from(tuple: (f32, f32, f32)) -> ValueResult<LchValue> {
            LchValue {
                l: tuple.0,
                c: tuple.1,
                h: tuple.2,
            }.validate()
        }
    }

    impl TryFrom<&(f32, f32, f32)> for LchValue {
        type Error = ValueError;
        fn try_from(tuple: &(f32, f32, f32)) -> ValueResult<LchValue> {
            LchValue {
                l: tuple.0,
                c: tuple.1,
                h: tuple.2,
            }.validate()
        }
    }

    // To Xyz /////////////////////////////////////////////////////////////////////
    impl From<LabValue> for XyzValue {
        fn from(lab: LabValue) -> XyzValue {
            let fy = (lab.l + 16.0) / 116.0;
            let fx = (lab.a / 500.0) + fy;
            let fz = fy - (lab.b / 200.0);
            let xr = if fx > CBRT_EPSILON as f32 {
                fx.powi(3)
            } else {
                ((fx * 116.0) - 16.0) / KAPPA
            };
            let yr = if lab.l > EPSILON * KAPPA {
                fy.powi(3)
            } else {
                lab.l / KAPPA
            };
            let zr = if fz > CBRT_EPSILON as f32 {
                fz.powi(3)
            } else {
                ((fz * 116.0) - 16.0) / KAPPA
            };

            XyzValue {
                x: xr * 0.9642,
                y: yr,
                z: zr * 0.8251,
            }
        }
    }

    impl From<&LabValue> for XyzValue {
        fn from(lab: &LabValue) -> XyzValue {
            XyzValue::from(*lab)
        }
    }

    impl From<LchValue> for XyzValue {
        fn from(lch: LchValue) -> XyzValue {
            XyzValue::from(LabValue::from(lch))
        }
    }

    impl From<&LchValue> for XyzValue {
        fn from(lch: &LchValue) -> XyzValue {
            XyzValue::from(*lch)
        }
    }

    impl TryFrom<&[f32; 3]> for XyzValue {
        type Error = ValueError;
        fn try_from(slice: &[f32; 3]) -> ValueResult<XyzValue> {
            XyzValue {
                x: slice[0],
                y: slice[1],
                z: slice[2]
            }.validate()
        }
    }

    impl TryFrom<(f32, f32, f32)> for XyzValue {
        type Error = ValueError;
        fn try_from(tuple: (f32, f32, f32)) -> ValueResult<XyzValue> {
            XyzValue {
                x: tuple.0,
                y: tuple.1,
                z: tuple.2,
            }.validate()
        }
    }

    impl TryFrom<&(f32, f32, f32)> for XyzValue {
        type Error = ValueError;
        fn try_from(tuple: &(f32, f32, f32)) -> ValueResult<XyzValue> {
            XyzValue {
                x: tuple.0,
                y: tuple.1,
                z: tuple.2,
            }.validate()
        }
    }

    // FromStr ////////////////////////////////////////////////////////////////////
    impl FromStr for DEMethod {
        type Err = std::io::Error;
        fn from_str(s: &str) -> Result<DEMethod, Self::Err> {
            match s.to_lowercase().trim() {
                "de2000"  | "de00"  | "2000"  | "00"  => Ok(DEMethod::DE2000),
                "de1976"  | "de76"  | "1976"  | "76"  => Ok(DEMethod::DE1976),
                "de1994"  | "de94"  | "1994"  | "94" |
                "de1994g" | "de94g" | "1994g" | "94g" => Ok(DEMethod::DE1994G),
                "de1994t" | "de94t" | "1994t" | "94t" => Ok(DEMethod::DE1994T),
                "decmc"   | "decmc1"| "cmc1"  | "cmc" => Ok(DEMethod::DECMC(1.0, 1.0)),
                "decmc2"  | "cmc2"                    => Ok(DEMethod::DECMC(2.0, 1.0)),
                _ => Err(io::Error::from(io::ErrorKind::InvalidInput)),
            }
        }
    }

    impl FromStr for LabValue {
        type Err = ValueError;
        fn from_str(s: &str) -> ValueResult<LabValue> {
            let split = parse_str_to_vecf32(s, 3)?;

            LabValue {
                l: split[0],
                a: split[1],
                b: split[2],
            }.validate()
        }
    }

    impl FromStr for LchValue {
        type Err = ValueError;
        fn from_str(s: &str) -> ValueResult<LchValue> {
            let split = parse_str_to_vecf32(s, 3)?;

            LchValue {
                l: split[0],
                c: split[1],
                h: split[2],
            }.validate()
        }
    }

    impl FromStr for XyzValue {
        type Err = ValueError;
        fn from_str(s: &str) -> ValueResult<XyzValue> {
            let split = parse_str_to_vecf32(s, 3)?;

            XyzValue {
                x: split[0],
                y: split[1],
                z: split[2],
            }.validate()
        }

    }

    // Helper Functions ////////////////////////////////////////////////////////////
    const KAPPA: f32 = 24389.0 / 27.0; // CIE Standard: 903.3
    const EPSILON: f32 = 216.0 / 24389.0; // CIE Standard: 0.008856
    const CBRT_EPSILON: f64 = 0.20689655172413796;

    pub fn get_h_prime(a: f32, b: f32) -> f32 {
        let h_prime = b.atan2(a).to_degrees();
        if h_prime < 0.0 {
            h_prime + 360.0
        } else {
            h_prime
        }
    }

    // Validate and convert strings to `LabValue`.
    // Split string by comma (92.5,33.5,-18.8).
    fn parse_str_to_vecf32(s: &str, length: usize) -> ValueResult<Vec<f32>> {
        let collection: Vec<&str> = s.split(',').collect();

        // Allow extraneous whitespace ("92.5, 33.5, -18.8")
        let mut v: Vec<&str> = Vec::new();
        for item in collection.iter() {
            if !item.is_empty() {
                v.push(item.trim());
            }
        }
        // Parse the f32's into a Vec
        let split: Vec<f32> = v.iter().filter_map(|s| s.parse().ok()).collect();

        // Check if it's the right number of items
        if v.len() != length || split.len() != length {
            return Err(ValueError::BadFormat);
        }

        Ok(split)
    }

    #[inline]
    fn xyz_to_lab_map(c: f32) -> f32 {
        if c > EPSILON {
            c.powf(1.0/3.0)
        } else {
            (KAPPA * c + 16.0) / 116.0
        }
    }