Struct palette::blend::PreAlpha

#[repr(C)]
pub struct PreAlpha<C, T: Float> {
    pub color: C,
    pub alpha: T,
}

Premultiplied alpha wrapper.

Premultiplied colors are commonly used in composition algorithms to simplify the calculations. It may also be preferred when interpolating between colors, which is one of the reasons why it’s offered as a separate type. The other reason is to make it easier to avoid unnecessary computations in composition chains.

use palette::{Blend, LinSrgb, LinSrgba};
use palette::blend::PreAlpha;

let a = PreAlpha::from(LinSrgba::new(0.4, 0.5, 0.5, 0.3));
let b = PreAlpha::from(LinSrgba::new(0.3, 0.8, 0.4, 0.4));
let c = PreAlpha::from(LinSrgba::new(0.7, 0.1, 0.8, 0.8));

let res = LinSrgb::from_premultiplied(a.screen(b).overlay(c));

Note that converting to and from premultiplied alpha will cause the alpha component to be clamped to [0.0, 1.0].

Fields

color: C

The premultiplied color components (original.color * original.alpha).

alpha: T

The transparency component. 0.0 is fully transparent and 1.0 is fully opaque.

Trait Implementations

impl<C, T> AbsDiffEq<PreAlpha<C, T>> for PreAlpha<C, T> where
    C: AbsDiffEq<Epsilon = T::Epsilon>,
    T: AbsDiffEq + Float,
    T::Epsilon: Copy, 

type Epsilon = <T as AbsDiffEq<T>>::Epsilon

Used for specifying relative comparisons.

fn default_epsilon() -> Self::Epsilon

The default tolerance to use when testing values that are close together.

fn abs_diff_eq(&self, other: &PreAlpha<C, T>, epsilon: Self::Epsilon) -> bool

A test for equality that uses the absolute difference to compute the approximate equality of two numbers.

fn abs_diff_ne(&self, other: &Rhs, epsilon: Self::Epsilon) -> bool

The inverse of AbsDiffEq::abs_diff_eq.

impl<C: Add, T: Float> Add<PreAlpha<C, T>> for PreAlpha<C, T>

type Output = PreAlpha<<C as Add<C>>::Output, T>

The resulting type after applying the + operator.

fn add(self, other: PreAlpha<C, T>) -> Self::Output

Performs the + operation.

impl<T: Float, C: Add<T>> Add<T> for PreAlpha<C, T>

type Output = PreAlpha<<C as Add<T>>::Output, T>

The resulting type after applying the + operator.

fn add(self, c: T) -> Self::Output

Performs the + operation.

impl<C: AddAssign, T: Float + AddAssign> AddAssign<PreAlpha<C, T>> for PreAlpha<C, T>

fn add_assign(&mut self, other: PreAlpha<C, T>)

Performs the += operation.

impl<T: Float + AddAssign, C: AddAssign<T>> AddAssign<T> for PreAlpha<C, T>

fn add_assign(&mut self, c: T)

Performs the += operation.

impl<C, T, P> AsMut<P> for PreAlpha<C, T> where
    C: Pixel<T>,
    T: Float,
    P: RawPixel<T> + ?Sized, 

fn as_mut(&mut self) -> &mut P

Converts this type into a mutable reference of the (usually inferred) input type.

impl<C, T, P> AsRef<P> for PreAlpha<C, T> where
    C: Pixel<T>,
    T: Float,
    P: RawPixel<T> + ?Sized, 

fn as_ref(&self) -> &P

Converts this type into a shared reference of the (usually inferred) input type.

impl<C, T> Blend for PreAlpha<C, T> where
    C: Blend<Color = C> + ComponentWise<Scalar = T>,
    T: Float, 

type Color = C

The core color type. Typically Self for color types without alpha.

fn into_premultiplied(self) -> PreAlpha<C, T>

Convert the color to premultiplied alpha.

fn from_premultiplied(color: PreAlpha<C, T>) -> PreAlpha<C, T>

Convert the color from premultiplied alpha.

fn blend<F>(self, destination: Self, blend_function: F) -> Self where
    F: BlendFunction<Self::Color>, 

Blend self, as the source color, with destination, using blend_function. Anything that implements BlendFunction is acceptable, including functions and closures.

fn over(self, other: Self) -> Self

Place self over other. This is the good old common alpha composition equation.

fn inside(self, other: Self) -> Self

Results in the parts of self that overlaps the visible parts of other.

fn outside(self, other: Self) -> Self

Results in the parts of self that lies outside the visible parts of other.

fn atop(self, other: Self) -> Self

Place self over only the visible parts of other.

fn xor(self, other: Self) -> Self

Results in either self or other, where they do not overlap.

fn plus(self, other: Self) -> Self

Add self and other. This uses the alpha component to regulate the effect, so it’s not just plain component wise addition.

fn multiply(self, other: Self) -> Self

Multiply self with other. This uses the alpha component to regulate the effect, so it’s not just plain component wise multiplication.

fn screen(self, other: Self) -> Self

Make a color which is at least as light as self or other.

fn overlay(self, other: Self) -> Self

Multiply self or other if other is dark, or screen them if other is light. This results in an S curve.

fn darken(self, other: Self) -> Self

Return the darkest parts of self and other.

fn lighten(self, other: Self) -> Self

Return the lightest parts of self and other.

fn dodge(self, other: Self) -> Self

Lighten other to reflect self. Results in other if self is black.

fn burn(self, other: Self) -> Self

Darken other to reflect self. Results in other if self is white.

fn hard_light(self, other: Self) -> Self

Multiply self or other if other is dark, or screen them if self is light. This is similar to overlay, but depends on self instead of other.

fn soft_light(self, other: Self) -> Self

Lighten other if self is light, or darken other as if it’s burned if self is dark. The effect is increased if the components of self is further from 0.5.

fn difference(self, other: Self) -> Self

Return the absolute difference between self and other. It’s basically abs(self - other), but regulated by the alpha component.

fn exclusion(self, other: Self) -> Self

Similar to difference, but appears to result in a lower contrast. other is inverted if self is white, and preserved if self is black.

impl<C: Clone, T: Clone + Float> Clone for PreAlpha<C, T>

fn clone(&self) -> PreAlpha<C, T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<C: ComponentWise<Scalar = T>, T: Float> ComponentWise for PreAlpha<C, T>

type Scalar = T

The scalar type for color components.

fn component_wise<F: FnMut(T, T) -> T>(
    &self,
    other: &PreAlpha<C, T>,
    f: F
) -> PreAlpha<C, T>

Perform a binary operation on this and an other color.

fn component_wise_self<F: FnMut(T) -> T>(&self, f: F) -> PreAlpha<C, T>

Perform a unary operation on this color.

impl<C: Debug, T: Debug + Float> Debug for PreAlpha<C, T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<C: Default, T: Float> Default for PreAlpha<C, T>

fn default() -> PreAlpha<C, T>

Returns the “default value” for a type.

impl<C, T: Float> Deref for PreAlpha<C, T>

type Target = C

The resulting type after dereferencing.

fn deref(&self) -> &C

Dereferences the value.

impl<C, T: Float> DerefMut for PreAlpha<C, T>

fn deref_mut(&mut self) -> &mut C

Mutably dereferences the value.

impl<C: Div, T: Float> Div<PreAlpha<C, T>> for PreAlpha<C, T>

type Output = PreAlpha<<C as Div<C>>::Output, T>

The resulting type after applying the / operator.

fn div(self, other: PreAlpha<C, T>) -> Self::Output

Performs the / operation.

impl<T: Float, C: Div<T>> Div<T> for PreAlpha<C, T>

type Output = PreAlpha<<C as Div<T>>::Output, T>

The resulting type after applying the / operator.

fn div(self, c: T) -> Self::Output

Performs the / operation.

impl<C: DivAssign, T: Float + DivAssign> DivAssign<PreAlpha<C, T>> for PreAlpha<C, T>

fn div_assign(&mut self, other: PreAlpha<C, T>)

Performs the /= operation.

impl<T: Float + DivAssign, C: DivAssign<T>> DivAssign<T> for PreAlpha<C, T>

fn div_assign(&mut self, c: T)

Performs the /= operation.

impl<C, T> From<Alpha<C, T>> for PreAlpha<C, T> where
    C: ComponentWise<Scalar = T>,
    T: Float, 

fn from(color: Alpha<C, T>) -> PreAlpha<C, T>

Converts to this type from the input type.

impl<C, T> From<PreAlpha<C, T>> for Alpha<C, T> where
    C: ComponentWise<Scalar = T>,
    T: Float, 

fn from(color: PreAlpha<C, T>) -> Alpha<C, T>

Converts to this type from the input type.

impl<C: Mix> Mix for PreAlpha<C, C::Scalar>

type Scalar = <C as Mix>::Scalar

The type of the mixing factor.

fn mix(
    &self,
    other: &PreAlpha<C, C::Scalar>,
    factor: C::Scalar
) -> PreAlpha<C, C::Scalar>

Mix the color with an other color, by factor.

impl<C: Mul, T: Float> Mul<PreAlpha<C, T>> for PreAlpha<C, T>

type Output = PreAlpha<<C as Mul<C>>::Output, T>

The resulting type after applying the * operator.

fn mul(self, other: PreAlpha<C, T>) -> Self::Output

Performs the * operation.

impl<T: Float, C: Mul<T>> Mul<T> for PreAlpha<C, T>

type Output = PreAlpha<<C as Mul<T>>::Output, T>

The resulting type after applying the * operator.

fn mul(self, c: T) -> Self::Output

Performs the * operation.

impl<C: MulAssign, T: Float + MulAssign> MulAssign<PreAlpha<C, T>> for PreAlpha<C, T>

fn mul_assign(&mut self, other: PreAlpha<C, T>)

Performs the *= operation.

impl<T: Float + MulAssign, C: MulAssign<T>> MulAssign<T> for PreAlpha<C, T>

fn mul_assign(&mut self, c: T)

Performs the *= operation.

impl<C, T> PartialEq<PreAlpha<C, T>> for PreAlpha<C, T> where
    T: Float + PartialEq,
    C: PartialEq, 

fn eq(&self, other: &Self) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=.

impl<T: Float, C: Pixel<T>> Pixel<T> for PreAlpha<C, T>

const CHANNELS: usize = C::CHANNELS + 1

The number of color channels.

fn as_raw<P: RawPixel<T> + ?Sized>(&self) -> &P

Cast as a reference to raw color components.

fn as_raw_mut<P: RawPixel<T> + ?Sized>(&mut self) -> &mut P

Cast as a mutable reference to raw color components.

fn into_raw<P: RawPixelSized<T>>(self) -> P

Convert into raw color components.

fn from_raw<P: RawPixel<T> + ?Sized>(pixel: &P) -> &Self

Cast from a reference to raw color components.

fn from_raw_mut<P: RawPixel<T> + ?Sized>(pixel: &mut P) -> &mut Self

Cast from a mutable reference to raw color components.

fn from_raw_slice(slice: &[T]) -> &[Self]

Cast a slice of raw color components to a slice of colors.

fn from_raw_slice_mut(slice: &mut [T]) -> &mut [Self]

Cast a mutable slice of raw color components to a mutable slice of colors.

fn into_raw_slice(slice: &[Self]) -> &[T]

Cast a slice of colors to a slice of raw color components.

fn into_raw_slice_mut(slice: &mut [Self]) -> &mut [T]

Cast a mutable slice of colors to a mutable slice of raw color components.

impl<C, T> RelativeEq<PreAlpha<C, T>> for PreAlpha<C, T> where
    C: RelativeEq<Epsilon = T::Epsilon>,
    T: RelativeEq + Float,
    T::Epsilon: Copy, 

fn default_max_relative() -> Self::Epsilon

The default relative tolerance for testing values that are far-apart.

fn relative_eq(
    &self,
    other: &PreAlpha<C, T>,
    epsilon: Self::Epsilon,
    max_relative: Self::Epsilon
) -> bool

A test for equality that uses a relative comparison if the values are far apart.

fn relative_ne(
    &self,
    other: &Rhs,
    epsilon: Self::Epsilon,
    max_relative: Self::Epsilon
) -> bool

The inverse of RelativeEq::relative_eq.

impl<C: Sub, T: Float> Sub<PreAlpha<C, T>> for PreAlpha<C, T>

type Output = PreAlpha<<C as Sub<C>>::Output, T>

The resulting type after applying the - operator.

fn sub(self, other: PreAlpha<C, T>) -> Self::Output

Performs the - operation.

impl<T: Float, C: Sub<T>> Sub<T> for PreAlpha<C, T>

type Output = PreAlpha<<C as Sub<T>>::Output, T>

The resulting type after applying the - operator.

fn sub(self, c: T) -> Self::Output

Performs the - operation.

impl<C: SubAssign, T: Float + SubAssign> SubAssign<PreAlpha<C, T>> for PreAlpha<C, T>

fn sub_assign(&mut self, other: PreAlpha<C, T>)

Performs the -= operation.

impl<T: Float + SubAssign, C: SubAssign<T>> SubAssign<T> for PreAlpha<C, T>

fn sub_assign(&mut self, c: T)

Performs the -= operation.

impl<C, T> UlpsEq<PreAlpha<C, T>> for PreAlpha<C, T> where
    C: UlpsEq<Epsilon = T::Epsilon>,
    T: UlpsEq + Float,
    T::Epsilon: Copy, 

fn default_max_ulps() -> u32

The default ULPs to tolerate when testing values that are far-apart.

fn ulps_eq(
    &self,
    other: &PreAlpha<C, T>,
    epsilon: Self::Epsilon,
    max_ulps: u32
) -> bool

A test for equality that uses units in the last place (ULP) if the values are far apart.

fn ulps_ne(&self, other: &Rhs, epsilon: Self::Epsilon, max_ulps: u32) -> bool

The inverse of UlpsEq::ulps_eq.

impl<C: Copy, T: Copy + Float> Copy for PreAlpha<C, T>

impl<C, T> Eq for PreAlpha<C, T> where
    T: Float + Eq,
    C: Eq,