From 93a410bafde630d9e3eb3563d6289d23627099a3 Mon Sep 17 00:00:00 2001 From: Camden Dixie O'Brien Date: Mon, 26 Oct 2026 13:13:44 +0000 Subject: [PATCH] Implement conversion between sRGB and linear RGB --- Cargo.lock | 398 ++++++++++++++++++++++++++++++++++++++++++++++ Cargo.toml | 3 + src/image/srgb.rs | 122 +++++++++++--- 3 files changed, 499 insertions(+), 24 deletions(-) diff --git a/Cargo.lock b/Cargo.lock index 0f0066d..b1c2b78 100644 --- a/Cargo.lock +++ b/Cargo.lock @@ -2,11 +2,73 @@ # It is not intended for manual editing. version = 4 +[[package]] +name = "autocfg" +version = "1.5.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "f2032f911046de80f0a198e0901378627c33f59ea0ac00e363d481118bd70a53" + +[[package]] +name = "bit-set" +version = "0.11.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "56d87354e4229f54a44f7bf2435906a4656dba36026ab6eaca629a2c436a691c" +dependencies = [ + "bit-vec", +] + +[[package]] +name = "bit-vec" +version = "0.10.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "5727b15fa97d4f4fee0a3b7c3d550ed0269f54329207b86388de918604e31269" +dependencies = [ + "borsh", + "serde", +] + +[[package]] +name = "bitflags" +version = "2.13.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3ded4057c258ba199e2d26386d3af3780957ecaee6c4ef4041c6b4b8b97c0b06" + +[[package]] +name = "borsh" +version = "1.8.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "553c5d846a6ba5150c65e3b1b8ec073bcf1abc20f9b7220de384a4443ea4e20a" +dependencies = [ + "borsh-derive", + "bytes", + "cfg_aliases", +] + +[[package]] +name = "borsh-derive" +version = "1.8.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "12cdfe656708a01f89b451a7d36466e6fe6c414de0aa18fc54f864f6f9ca9f56" +dependencies = [ + "once_cell", + "proc-macro-crate", + "proc-macro2", + "quote", + "syn", +] + +[[package]] +name = "bytes" +version = "1.12.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "fc652a48c352aef3ea3aed32080501cf3ef6ed5da78602a020c991775b0aff04" + [[package]] name = "ccvl" version = "0.1.0" dependencies = [ "ccvl_proc_macros", + "proptest", ] [[package]] @@ -17,6 +79,142 @@ dependencies = [ "syn", ] +[[package]] +name = "cfg-if" +version = "1.0.5" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "4e7648175b45a9a48536d676f68d918270699102aa8dab5496df06904c914600" + +[[package]] +name = "cfg_aliases" +version = "0.2.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "f079e83a288787bcd14a6aea84cee5c87a67c5a3e660c30f557a3d24761b3527" + +[[package]] +name = "chacha20" +version = "0.10.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "65c35e4b699c7e15ccbe7ee35c005e4fc0a278d22238a2857e6ce2dadeda1b06" +dependencies = [ + "cfg-if", + "cpufeatures", + "rand_core", +] + +[[package]] +name = "core_detect" +version = "1.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "7f8f80099a98041a3d1622845c271458a2d73e688351bf3cb999266764b81d48" + +[[package]] +name = "cpufeatures" +version = "0.3.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "5ca28b0ae3115b884660db4118d803791fd6756b6e88f39c0f3f7859060d7566" +dependencies = [ + "libc", +] + +[[package]] +name = "equivalent" +version = "1.0.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "00d174d5400e5e8fd687ad1049e2f578285fa914201b1af7e8b112a4546bd826" + +[[package]] +name = "errno" +version = "0.3.14" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "39cab71617ae0d63f51a36d69f866391735b51691dbda63cf6f96d042b63efeb" +dependencies = [ + "libc", + "windows-sys", +] + +[[package]] +name = "fastrand" +version = "2.5.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "da7c62ceae207dd37ea5b845da6a0696c799f85e97da1ab5b7910be3c1c80223" + +[[package]] +name = "fnv" +version = "1.0.7" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1" + +[[package]] +name = "getrandom" +version = "0.4.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "300e883d756b2e4ec94e02791f39b04b522276138852cfc41d9fb7e904106099" +dependencies = [ + "cfg-if", + "libc", + "r-efi", + "rand_core", +] + +[[package]] +name = "hashbrown" +version = "0.17.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ed5909b6e89a2db4456e54cd5f673791d7eca6732202bbf2a9cc504fe2f9b84a" + +[[package]] +name = "indexmap" +version = "2.14.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "cc4e190f5d26ca7051642629da2c52fc03bde85a03197c99408dcd291734c855" +dependencies = [ + "equivalent", + "hashbrown", +] + +[[package]] +name = "libc" +version = "0.2.191" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "65cd87c9a6d60536580b316ad985726104730a5151c99845f2490428ef91240a" + +[[package]] +name = "linux-raw-sys" +version = "0.12.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "32a66949e030da00e8c7d4434b251670a91556f4144941d37452769c25d58a53" + +[[package]] +name = "memchr" +version = "2.8.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "cf8baf1c55e62ffcace7a9f06f4bd9cd3f0c4beb022d3b367256b91b87513d98" + +[[package]] +name = "num-traits" +version = "0.2.19" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "071dfc062690e90b734c0b2273ce72ad0ffa95f0c74596bc250dcfd960262841" +dependencies = [ + "autocfg", +] + +[[package]] +name = "once_cell" +version = "1.21.4" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "9f7c3e4beb33f85d45ae3e3a1792185706c8e16d043238c593331cc7cd313b50" + +[[package]] +name = "proc-macro-crate" +version = "3.5.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e67ba7e9b2b56446f1d419b1d807906278ffa1a658a8a5d8a39dcb1f5a78614f" +dependencies = [ + "toml_edit", +] + [[package]] name = "proc-macro2" version = "1.0.107" @@ -26,6 +224,32 @@ dependencies = [ "unicode-ident", ] +[[package]] +name = "proptest" +version = "1.12.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "b8530004ccb15eae51c7e40009fbe317f341f804db54dc033eec1c50be28cfa0" +dependencies = [ + "bit-set", + "bit-vec", + "bitflags", + "chacha20", + "core_detect", + "num-traits", + "rand", + "rand_xorshift", + "regex-syntax", + "rusty-fork", + "tempfile", + "unarray", +] + +[[package]] +name = "quick-error" +version = "1.2.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0" + [[package]] name = "quote" version = "1.0.47" @@ -35,6 +259,98 @@ dependencies = [ "proc-macro2", ] +[[package]] +name = "r-efi" +version = "6.0.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "f8dcc9c7d52a811697d2151c701e0d08956f92b0e24136cf4cf27b57a6a0d9bf" + +[[package]] +name = "rand" +version = "0.10.3" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "65c9fb96cbc91e3478eaae79a69fcd3f1ae4ad052e471fe6732fff548984b4af" +dependencies = [ + "getrandom", + "rand_core", +] + +[[package]] +name = "rand_core" +version = "0.10.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "63b8176103e19a2643978565ca18b50549f6101881c443590420e4dc998a3c69" + +[[package]] +name = "rand_xorshift" +version = "0.5.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "60aa6af80be32871323012e02e6e65f8a7cc7890931ae421d217ad8fe0df2ccf" +dependencies = [ + "rand_core", +] + +[[package]] +name = "regex-syntax" +version = "0.8.11" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "d6f6ff9a378485b298a5286656da665ba74413d36db0979633275d2e708145d4" + +[[package]] +name = "rustix" +version = "1.1.5" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "891efababe418670775f199f0d233d84843c227a0949a883ce15b37c78d6629d" +dependencies = [ + "bitflags", + "errno", + "libc", + "linux-raw-sys", + "windows-sys", +] + +[[package]] +name = "rusty-fork" +version = "0.3.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "cc6bf79ff24e648f6da1f8d1f011e9cac26491b619e6b9280f2b47f1774e6ee2" +dependencies = [ + "fnv", + "quick-error", + "tempfile", + "wait-timeout", +] + +[[package]] +name = "serde" +version = "1.0.229" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "4148590afebada386688f18773da617792bf2ef03ffc1e4cbd2b1d45b023e0ba" +dependencies = [ + "serde_core", + "serde_derive", +] + +[[package]] +name = "serde_core" +version = "1.0.229" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "67dca2c9c51e58a4791a4b1ed58308b39c64224d349a935ab5039aa360942a48" +dependencies = [ + "serde_derive", +] + +[[package]] +name = "serde_derive" +version = "1.0.229" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e7a5d71263a5a7d47b41f6b3f06ba276f10cc18b0931f1799f710578e2309348" +dependencies = [ + "proc-macro2", + "quote", + "syn", +] + [[package]] name = "syn" version = "3.0.9" @@ -46,8 +362,90 @@ dependencies = [ "unicode-ident", ] +[[package]] +name = "tempfile" +version = "3.27.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "32497e9a4c7b38532efcdebeef879707aa9f794296a4f0244f6f69e9bc8574bd" +dependencies = [ + "fastrand", + "getrandom", + "once_cell", + "rustix", + "windows-sys", +] + +[[package]] +name = "toml_datetime" +version = "1.1.2+spec-1.1.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "2b86d767906c6c42421dcba507eb9d203e779497710a47782a224bb871653053" +dependencies = [ + "serde_core", +] + +[[package]] +name = "toml_edit" +version = "0.25.17+spec-1.1.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "e3641d5bbb5349a79e1020a242d251efbc546ad8048d133958323ce9c40a9c9c" +dependencies = [ + "indexmap", + "toml_datetime", + "toml_parser", + "winnow", +] + +[[package]] +name = "toml_parser" +version = "1.1.5+spec-1.1.0" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "baa693a8032d7e1cada7d0041e96126df243179ff061456783ac7f12bda4744c" +dependencies = [ + "winnow", +] + +[[package]] +name = "unarray" +version = "0.1.4" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "eaea85b334db583fe3274d12b4cd1880032beab409c0d774be044d4480ab9a94" + [[package]] name = "unicode-ident" version = "1.0.27" source = "registry+https://github.com/rust-lang/crates.io-index" checksum = "a2c754d6c33795a1c324727428e5a7dedb5b06195f9890bdbcba760d3e246563" + +[[package]] +name = "wait-timeout" +version = "0.2.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "09ac3b126d3914f9849036f826e054cbabdc8519970b8998ddaf3b5bd3c65f11" +dependencies = [ + "libc", +] + +[[package]] +name = "windows-link" +version = "0.2.1" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "f0805222e57f7521d6a62e36fa9163bc891acd422f971defe97d64e70d0a4fe5" + +[[package]] +name = "windows-sys" +version = "0.61.2" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "ae137229bcbd6cdf0f7b80a31df61766145077ddf49416a728b02cb3921ff3fc" +dependencies = [ + "windows-link", +] + +[[package]] +name = "winnow" +version = "1.0.4" +source = "registry+https://github.com/rust-lang/crates.io-index" +checksum = "23b97319f7b8343df12cc98938e5c3eb436064524c8d2b4e30a1d3a36eecdf81" +dependencies = [ + "memchr", +] diff --git a/Cargo.toml b/Cargo.toml index 0ca21fb..65fad78 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -5,3 +5,6 @@ edition = "2024" [dependencies] ccvl_proc_macros = { path = "proc_macros" } + +[dev-dependencies] +proptest = "1.12.0" diff --git a/src/image/srgb.rs b/src/image/srgb.rs index 1551ed4..aeec0e6 100644 --- a/src/image/srgb.rs +++ b/src/image/srgb.rs @@ -1,3 +1,5 @@ +use super::*; + use ccvl_proc_macros::Pixel; #[derive(Clone, Copy, Debug, PartialEq, Pixel)] @@ -15,6 +17,29 @@ pub struct SRGB { pub b: f32, } +const CUTOFF: f32 = 4.05e-2; +const LINEAR_DIVISOR: f32 = 12.92; +const SHIFT: f32 = 5.5e-2; +const DIVISOR: f32 = 1.055; +const POWER: f32 = 2.4; +const INVERSE_CUTOFF: f32 = 3.1308e-3; + +pub fn to_linear(c: f32) -> f32 { + if c <= CUTOFF { + c / LINEAR_DIVISOR + } else { + ((c + SHIFT) / DIVISOR).powf(POWER) + } +} + +pub fn from_linear(c: f32) -> f32 { + if c <= INVERSE_CUTOFF { + c * LINEAR_DIVISOR + } else { + c.powf(1.0 / POWER) * DIVISOR - SHIFT + } +} + impl SRGBA { pub fn new(r: f32, g: f32, b: f32, a: f32) -> Self { Self { r, g, b, a } @@ -22,9 +47,9 @@ impl SRGBA { } impl Into for SRGBA { - fn into(self) -> SRGB { - SRGB::new(self.r, self.g, self.b) - } + fn into(self) -> SRGB { + SRGB::new(self.r, self.g, self.b) + } } impl SRGB { @@ -34,31 +59,80 @@ impl SRGB { } impl Into for SRGB { - fn into(self) -> SRGBA { - SRGBA::new(self.r, self.g, self.b, 1.0) - } + fn into(self) -> SRGBA { + SRGBA::new(self.r, self.g, self.b, 1.0) + } +} + +impl Into for SRGB { + fn into(self) -> LinearRGB { + LinearRGB::new( + to_linear(self.r), + to_linear(self.g), + to_linear(self.b), + ) + } +} + +impl From for SRGB { + fn from(linear: LinearRGB) -> Self { + Self::new( + from_linear(linear.r), + from_linear(linear.g), + from_linear(linear.b), + ) + } } #[cfg(test)] mod tests { - use super::*; + use super::*; + use proptest::prelude::*; - #[test] - fn srgb_from_srgba_drops_alpha() - { - let srgb: SRGB = SRGBA::new(0.1, 0.2, 0.3, 0.4).into(); - assert_eq!(srgb.r, 0.1); - assert_eq!(srgb.g, 0.2); - assert_eq!(srgb.b, 0.3); - } + macro_rules! prop_assert_approx { + ( $act:expr, $exp:expr ) => { + prop_assert!(($act - $exp).abs() < 1e-6) + }; + } - #[test] - fn srgba_from_srgb_adds_alpha_1() - { - let srgba: SRGBA = SRGB::new(0.1, 0.2, 0.3).into(); - assert_eq!(srgba.r, 0.1); - assert_eq!(srgba.g, 0.2); - assert_eq!(srgba.b, 0.3); - assert_eq!(srgba.a, 1.0); - } + proptest! { + #[test] + fn srgb_from_srgba_drops_alpha( + r in 0.0f32..1.0, + g in 0.0f32..1.0, + b in 0.0f32..1.0, + a in 0.0f32..1.0, + ) { + let res: SRGB = SRGBA::new(r, g, b, a).into(); + prop_assert_eq!(res.r, r); + prop_assert_eq!(res.g, g); + prop_assert_eq!(res.b, b); + } + + #[test] + fn srgba_from_srgb_adds_alpha_1( + r in 0.0f32..1.0, + g in 0.0f32..1.0, + b in 0.0f32..1.0, + ) { + let res: SRGBA = SRGB::new(r, g, b).into(); + prop_assert_eq!(res.r, r); + prop_assert_eq!(res.g, g); + prop_assert_eq!(res.b, b); + prop_assert_eq!(res.a, 1.0); + } + + #[test] + fn approx_unchanged_from_linear_round_trip( + r in 0.0f32..1.0, + g in 0.0f32..1.0, + b in 0.0f32..1.0, + ) { + let lin: LinearRGB = SRGB::new(r, g, b).into(); + let res: SRGB = lin.into(); + prop_assert_approx!(res.r, r); + prop_assert_approx!(res.g, g); + prop_assert_approx!(res.b, b); + } + } }