Mojo struct 🡭

GradientStops

@memory_only
struct GradientStops

A one-dimensional color ramp: stops sorted by offset, and the interpolated color at any position in [0, 1]. The half of every gradient that does not depend on geometry, and on its own the color scale a data value maps through once it is normalized.

Index, measure and iterate it like a list: len(stops), stops[i] and for stop in stops.

Implemented traits

AnyType, Copyable, Deinitable, Movable, Sized

Methods

__init__

fn def __init__(out self)

A ramp with no stops yet; color_at returns transparent black until one is added.

Args:

• self (Self)

Returns:

Self

__getitem__

fn def __getitem__(self, i: Int) -> GradientStop

Args:

• self (Self)
• i (Int)

Returns:

GradientStop

set_color_space

fn def set_color_space(mut self, space: ColorSpace)

Set the space color_at interpolates in: SRGB, the default, mixes the stops’ channel bytes directly; LINEAR mixes them in linear light (see ColorSpace), which keeps a ramp between two saturated colors from sagging through a dark middle. Alpha interpolates the same way in both. SvgCanvas writes a LINEAR ramp with color-interpolation="linearRGB".

Args:

• self (Self)
• space (ColorSpace): The space the ramp interpolates in.

color_space

fn def color_space(self) -> ColorSpace

The space color_at interpolates in.

Args:

• self (Self)

Returns:

ColorSpace: The current space, ColorSpace.SRGB until set_color_space says otherwise.

__len__

fn def __len__(self) -> Int

Args:

• self (Self)

Returns:

Int

__iter__

fn def __iter__(ref self) -> _ListIter[GradientStop, origin_of(self._stops)]

Args:

• self (Self)

Returns:

_ListIter[GradientStop, origin_of(self._stops)]

add_stop

fn def add_stop(mut self, offset: Float64, color: Color)

Add a stop, keeping the ramp sorted by offset with insertion order preserved among equal offsets.

Two stops at one offset are a hard color transition, and which was added first decides which side of it owns which color – so the insert goes after any stop already at this offset, and color_at reads the run’s ends accordingly.

Args:

• self (Self)
• offset (Float64): Position 0.0 to 1.0. Stops need not be added in order.
• color (Color): This stop’s color.

color_at

fn def color_at(self, t_in: Float64) -> Color

The ramp’s color at t_in, clamped to [0, 1] first (the “pad” extend), interpolated between the two stops bracketing it. The bracketing pair comes from a binary search over the sorted stops.

This runs once per pixel of every gradient fill, so the stops are read through a pointer rather than copied out of the list per probe, and the span it lands in carries its own reciprocal and channel deltas (_Interval) rather than deriving them again. What is left per pixel is a search, a multiply and one four-lane multiply-add.

Args:

• self (Self)
• t_in (Float64): Position along the ramp.

Returns:

Color: The interpolated color, transparent black if no stops have been added yet.