2 releases (1 stable)
|1.0.0||May 9, 2021|
|0.1.0||May 6, 2021|
#67 in Rendering
361 downloads per month
Used in 3 crates (2 directly)
Small crate implementing fast conversion between linear float and 8-bit sRGB. Includes API for performing 4 simultaneous conversions, which are SIMD accelerated using SSE2 if available. Supports no_std (doesn't need
f32_to_srgb8: converting a linear
u8. Compliant with the most relevent public spec for this conversion (correct to ULP of 0.6, monotonic over range, etc)
f32x4_to_srgb8: Produces results identical to calling
f32_to_srgb84 times in a row, but uses SSE2 to SIMD accelerate on
x86_64where SSE2 is known to be present. Otherwise, it just returns the results of calling
f32_to_srgb8(the scalar equivalent) 4 times.
srgb8_to_f32: Inverse operation of
f32_to_srgb8. Uses the standard technique of a 256-item lookup table.
- Huge performance improvments over the naive implementation — ~5x for conversion to f32->srgb8, ~20x for srgb8->f32.
no_std— normally this is tricky, as these operations require
powfnaively, which is not available to libcore.
- No dependencies.
- SIMD support for conversion to sRGB (conversion from sRGB is already ~20x faster than naive impl, and would probably be slower in SIMD, so for now it's not implemented).
- Consistent and correct (according to at least one relevant spec) handling of edge cases, such as NaN/Inf/etc.
- Exhaustive checking of all inputs for correctness (in tests).
# Measures `fast_srgb8::f32_to_srgb8` vs ref impl test tests::bench::fast_scalar ... bench: 144 ns/iter (+/- 11) test tests::bench::naive_scalar ... bench: 971 ns/iter (+/- 48) # Measures `fast_srgb8::f32x4_to_srgb8` vs calling reference impl 4 times test tests::bench::fast_f32x4 ... bench: 440 ns/iter (+/- 29) test tests::bench::naive_f32x4 ... bench: 3,625 ns/iter (+/- 282) test tests::bench::fast_f32x4_nosimd ... bench: 482 ns/iter (+/- 27) # Measures `fast_srgb8::srgb8_to_f32` vs ref impl test tests::bench::fast_from_srgb8 ... bench: 81 ns/iter (+/- 6) test tests::bench::naive_from_srgb8 ... bench: 4,026 ns/iter (+/- 282)
(Note that the
ns/iter time is not for a single invocation of these function, it's for several)
Public domain, as explained here. If that's unacceptable, it's also available under either the Apache-2.0 or MIT licenses, at your option.
The float->srgb code is originally¹ based on public domain routines by Fabien "ryg" Giesen, although I'm no longer sure where these are available.
¹ (Well, specifically: The Rust code in this crate is ported from code in a C++ game engine of mine, which in turn, was based on the code from ryg. This doesn't make a difference, but increases the likelihood that any errors are solely my responsibility).