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//! Immutable image sampling contracts, independent of decoding and rendering.
use std::{any::Any, fmt::Debug};
/// Texture reconstruction requested by a drawing command.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum Sampling {
/// Nearest base-level texel.
Nearest,
/// Bilinear base-level reconstruction.
Bilinear,
/// Bilinear reconstruction between adjacent mip levels.
#[default]
Trilinear,
}
/// A predecoded immutable linear-premultiplied image mip chain.
/// Content owns decoding/storage; backends consume this shared logical contract.
pub trait ImagePixels: Any + Debug + Send + Sync {
/// Base-level width in texels.
fn width(&self) -> u32;
/// Base-level height in texels.
fn height(&self) -> u32;
/// Number of immutable mip levels.
fn level_count(&self) -> usize;
/// Width/height of an existing mip level.
fn level_size(&self, level: usize) -> (u32, u32);
/// One in-bounds finite linear-premultiplied texel.
fn texel(&self, level: usize, column: usize, row: usize) -> [f32; 4];
/// Appends every texel of an existing level in row-major order, four `f32` each.
/// Overriding this avoids one dynamic call per texel for backends that upload whole levels.
fn extend_level(&self, level: usize, out: &mut Vec<f32>) {
let (width, height) = self.level_size(level);
out.reserve(width as usize * height as usize * 4);
for row in 0..height as usize {
for column in 0..width as usize {
out.extend(self.texel(level, column, row));
}
}
}
/// Whether another implementation owns the same immutable pixel content.
fn content_eq(&self, other: &dyn ImagePixels) -> bool;
/// Concrete storage identity, resolved only by its owning content implementation.
fn as_any(&self) -> &dyn Any;
}