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Switch to CIE XYZ lookup tables.

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This commit is contained in:
Nathan Vegdahl 2022-08-01 22:04:14 -07:00
parent caed4c67de
commit 8bc6b24004
3 changed files with 44 additions and 12 deletions
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7
Cargo.lock generated
View File

@ -127,6 +127,12 @@ dependencies = [
name = "color"
version = "0.1.0"
[[package]]
name = "colorbox"
version = "0.3.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "3d27d55561009760957654f467735e73806f8bc2d081cc4a22e93403ecd156fc"
[[package]]
name = "compact"
version = "0.1.0"
@ -329,6 +335,7 @@ dependencies = [
"bvh_order",
"clap",
"color",
"colorbox",
"compact",
"copy_in_place",
"crossbeam",

2
Cargo.toml
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@ -36,7 +36,7 @@ rustc-serialize = "0.3"
scoped_threadpool = "0.1"
time = "0.1"
fastapprox = "0.3"
colorbox = "0.3"
# Local crate dependencies

47
src/color.rs
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@ -608,21 +608,46 @@ fn xyz_to_spectrum_4(xyz: (f32, f32, f32), wavelengths: Float4) -> Float4 {
/// From the paper "Simple Analytic Approximations to the CIE XYZ Color Matching
/// Functions" by Wyman et al.
pub fn x_1931(wavelength: f32) -> f32 {
let t1 = (wavelength - 442.0) * (if wavelength < 442.0 { 0.0624 } else { 0.0374 });
let t2 = (wavelength - 599.8) * (if wavelength < 599.8 { 0.0264 } else { 0.0323 });
let t3 = (wavelength - 501.1) * (if wavelength < 501.1 { 0.0490 } else { 0.0382 });
(0.362 * fast_exp(-0.5 * t1 * t1)) + (1.056 * fast_exp(-0.5 * t2 * t2))
- (0.065 * fast_exp(-0.5 * t3 * t3))
use colorbox::tables::cie_1931_xyz::{MAX_WAVELENGTH, MIN_WAVELENGTH, X};
let norm = 1.0 / (MAX_WAVELENGTH - MIN_WAVELENGTH);
let n = (wavelength - MIN_WAVELENGTH) * norm;
if n < 0.0 {
X[0]
} else if n > 1.0 {
*X.last().unwrap()
} else {
crate::lerp::lerp_slice(X, n)
}
}
pub fn y_1931(wavelength: f32) -> f32 {
let t1 = (wavelength - 568.8) * (if wavelength < 568.8 { 0.0213 } else { 0.0247 });
let t2 = (wavelength - 530.9) * (if wavelength < 530.9 { 0.0613 } else { 0.0322 });
(0.821 * fast_exp(-0.5 * t1 * t1)) + (0.286 * fast_exp(-0.5 * t2 * t2))
use colorbox::tables::cie_1931_xyz::{MAX_WAVELENGTH, MIN_WAVELENGTH, Y};
let norm = 1.0 / (MAX_WAVELENGTH - MIN_WAVELENGTH);
let n = (wavelength - MIN_WAVELENGTH) * norm;
if n < 0.0 {
Y[0]
} else if n > 1.0 {
*Y.last().unwrap()
} else {
crate::lerp::lerp_slice(Y, n)
}
}
pub fn z_1931(wavelength: f32) -> f32 {
let t1 = (wavelength - 437.0) * (if wavelength < 437.0 { 0.0845 } else { 0.0278 });
let t2 = (wavelength - 459.0) * (if wavelength < 459.0 { 0.0385 } else { 0.0725 });
(1.217 * fast_exp(-0.5 * t1 * t1)) + (0.681 * fast_exp(-0.5 * t2 * t2))
use colorbox::tables::cie_1931_xyz::{MAX_WAVELENGTH, MIN_WAVELENGTH, Z};
let norm = 1.0 / (MAX_WAVELENGTH - MIN_WAVELENGTH);
let n = (wavelength - MIN_WAVELENGTH) * norm;
if n < 0.0 {
Z[0]
} else if n > 1.0 {
*Z.last().unwrap()
} else {
crate::lerp::lerp_slice(Z, n)
}
}