eq.rs - source
Description: Source of the Rust file `src/eq.rs`.
Keywords: rust, rustlang, rust-lang

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    //! ## `Tolerance` and `DeltaEq` traits
    //!
    //! This module deals with comparing two colors by [`DeltaE`] within a certain [`Tolerance`].
    //!
    //! See also: [`assert_delta_eq`]
    //!
    //! ### Implementing `Tolerance` and `DeltaEq`
    //!
    //! ```
    //! use deltae::*;
    //!
    //! struct MyTolerance(f32);
    //!
    //! impl Tolerance for MyTolerance {
    //!     fn tolerance(self) -> f32 {
    //!         self.0
    //!     }
    //! }
    //!
    //! #[derive(Copy, Clone)]
    //! struct MyLab(f32, f32, f32);
    //!
    //! // Types that implement Into<Lab> also implement the Delta trait
    //! impl From<MyLab> for LabValue {
    //!     fn from(mylab: MyLab) -> LabValue {
    //!         LabValue {
    //!             l: mylab.0,
    //!             a: mylab.1,
    //!             b: mylab.2,
    //!         }
    //!     }
    //! }
    //!
    //! impl<D: Delta + Copy> DeltaEq<D> for MyLab {}
    //!
    //! let mylab = MyLab(89.73, 1.88, -6.96);
    //! let lab = LabValue::new(89.73, 1.88, -6.96).unwrap();
    //! let de2000 = mylab.delta(lab, DEMethod::DE2000);
    //! assert!(mylab.delta_eq(&lab, DE1976, 0.0));
    //! ```
    use crate::*;

    /// Trait to determine whether two values are within a certain tolerance of [`DeltaE`]. Types that
    /// implement Into<[`LabValue`]> implicitly implement [`Delta`]. Types that implement [`Delta`] and
    /// [`Copy`] may also implement DeltaEq for other types that also implement [`Delta`] and [`Copy`].
    /// ```
    /// use deltae::*;
    ///
    /// #[derive(Copy, Clone)]
    /// struct MyLab(f32, f32, f32);
    ///
    /// // Types that implement Into<Lab> implicitly implement the Delta trait
    /// impl From<MyLab> for LabValue {
    ///     fn from(mylab: MyLab) -> LabValue {
    ///         LabValue {
    ///             l: mylab.0,
    ///             a: mylab.1,
    ///             b: mylab.2,
    ///         }
    ///     }
    /// }
    ///
    /// // Types that implement Delta and Copy may also implement DeltaEq for other types that also
    /// // implement Delta and Copy
    /// impl<D: Delta + Copy> DeltaEq<D> for MyLab {}
    ///
    /// let mylab = MyLab(89.73, 1.88, -6.96);
    /// let lab = LabValue::new(89.73, 1.88, -6.96).unwrap();
    /// let de2000 = mylab.delta(lab, DEMethod::DE2000);
    /// assert!(mylab.delta_eq(&lab, DE1976, 0.0));
    /// ```
    pub trait DeltaEq<D: Delta + Copy>: Delta + Copy {
        /// Return true if the value is less than or equal to the [`Tolerance`]
        fn delta_eq<T: Tolerance>(&self, other: D, method: DEMethod, tolerance: T) -> bool {
            self.delta(other, method).value() <= &tolerance.tolerance()
        }
    }

    /// Convenience macro for asserting two values are equivalent within a tolerance
    /// ```
    /// use deltae::*;
    ///
    /// let lab0 = LabValue::new(50.0, 0.0, 0.0).unwrap();
    /// let lab1 = LabValue::new(50.1, 0.1, 0.1).unwrap();
    ///
    /// // Assert that the difference between lab0 and lab1 is less than 1.0 DE2000
    /// assert_delta_eq!(lab0, lab1, DE2000, 1.0);
    /// ```
    #[macro_export]
    macro_rules! assert_delta_eq {
        ($reference:expr, $sample:expr, $method:expr, $tolerance:expr) => {
            assert!($reference.delta_eq($sample, $method, $tolerance))
        };
        ($reference:expr, $sample:expr, $method:expr, $tolerance:expr, $($message:tt)*) => {
            assert!($reference.delta_eq($sample, $method, $tolerance), $($message)*)
        };
    }

    /// Trait to define a tolerance value for the [`DeltaEq`] trait
    pub trait Tolerance {
        /// Return a tolerance value
        fn tolerance(self) -> f32;
    }

    impl Tolerance for f32 {
        fn tolerance(self) -> f32 {
            self
        }
    }

    impl Tolerance for f64 {
        fn tolerance(self) -> f32 {
            self as f32
        }
    }

    impl Tolerance for DeltaE {
        fn tolerance(self) -> f32 {
            self.value
        }
    }

    macro_rules! impl_delta_eq {
        ($t:ty) => {
            impl<D: Delta + Copy> DeltaEq<D> for $t {}
        }
    }

    impl_delta_eq!(LabValue);
    impl_delta_eq!(LchValue);
    impl_delta_eq!(XyzValue);