Struct ChromaKeyParams 

pub struct ChromaKeyParams {
    pub key_r: f32,
    pub key_g: f32,
    pub key_b: f32,
    pub similarity: f32,
    pub blend: f32,
    pub spill: f32,
    pub bg_r: f32,
    pub bg_g: f32,
    pub bg_b: f32,
    /* private fields */
}

Parameters for chroma_key. Default keys a pure-green screen and composites the foreground over black.

similarity and blend use FFmpeg chromakey semantics on FFmpeg’s scale (the same RGB→CbCr coefficients and √(d²/2) normalization, so 1.0 spans the full CbCr plane diagonal): distance ≤ similarity is background, the next blend of distance ramps linearly to foreground, and blend ≈ 0 degenerates to a hard threshold. One structural difference: FFmpeg compares the source’s RAW chroma plane codes against a BT.601-converted key, while this shader decodes the pixel to RGB first and projects both sides through the one BT.601 conversion. The two agree (within quantization) only on full-range BT.601 input; on any other range/matrix combination FFmpeg’s raw-code comparison carries a small built-in bias this implementation does not reproduce — treat ported ffmpeg -vf chromakey=... values as a close starting point, not bit-identical.

Fields

key_r: f32

Key color red, 0.0..=1.0.

key_g: f32

Key color green, 0.0..=1.0.

key_b: f32

Key color blue, 0.0..=1.0.

similarity: f32

Chroma distance keyed as background, 0.00001..=1.0. Larger keys more; neutral gray sits ≈ 0.38 from pure green on this scale.

blend: f32

Width of the soft edge past similarity, 0.0..=1.0; 0.0 is a hard binary matte.

spill: f32

Spill suppression strength, 0.0..=1.0: how strongly the key’s dominant channel is clamped toward the mean of the other two in surviving foreground (1.0 = FFmpeg despill defaults).

bg_r: f32

Background red, 0.0..=1.0.

bg_g: f32

Background green, 0.0..=1.0.

bg_b: f32

Background blue, 0.0..=1.0.

Implementations

impl ChromaKeyParams

pub fn green_screen() -> Self

Keys a pure-green screen (#00FF00) over black.

pub fn blue_screen() -> Self

Keys a pure-blue screen (#0000FF) over black.

pub fn with_background(self, r: f32, g: f32, b: f32) -> Self

Replaces the background color the foreground is composited over.

Trait Implementations

impl Clone for ChromaKeyParams

fn clone(&self) -> ChromaKeyParams

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for ChromaKeyParams

impl Debug for ChromaKeyParams

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

Formats the value using the given formatter.

impl Default for ChromaKeyParams

fn default() -> Self

Returns the “default value” for a type.

impl PartialEq for ChromaKeyParams

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

Equality operator ==.

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

Inequality operator !=.

impl Pod for ChromaKeyParams

impl StructuralPartialEq for ChromaKeyParams

impl Zeroable for ChromaKeyParams

fn zeroed() -> Self

Calls zeroed.