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Cleaning up the code in fluv32 a bit.

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This commit is contained in:
Nathan Vegdahl 2020-09-21 11:54:14 +09:00
parent 066105b20a
commit 9cf5ebdf91
1 changed files with 16 additions and 24 deletions
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40
sub_crates/trifloat/src/fluv32.rs
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@ -125,19 +125,10 @@ pub fn encode(xyz: (f32, f32, f32)) -> u32 {
/// Decodes from 32-bit FloatLuv to CIE XYZ. /// Decodes from 32-bit FloatLuv to CIE XYZ.
#[inline] #[inline]
pub fn decode(fluv32: u32) -> (f32, f32, f32) { pub fn decode(fluv32: u32) -> (f32, f32, f32) {
// Check for zero.
if fluv32 & 0xffff0000 == 0 {
return (0.0, 0.0, 0.0);
}
// Unpack values. // Unpack values.
let l_exp = fluv32 >> 26; let (y, u, v) = decode_yuv(fluv32);
let l_mant = (fluv32 >> 16) & 0x3ff; let u = u as f32;
let u = ((fluv32 >> 8) & 0xff) as f32; // Range 0.0-255.0 let v = v as f32;
let v = (fluv32 & 0xff) as f32; // Range 1.0-255.0
// Calculate y.
let y = f32::from_bits(((l_exp + 127 - EXP_BIAS as u32) << 23) | (l_mant << 13));
// Calculate x and z. // Calculate x and z.
// This is re-worked from the original equations, to allow a bunch of stuff // This is re-worked from the original equations, to allow a bunch of stuff
@ -146,9 +137,10 @@ pub fn decode(fluv32: u32) -> (f32, f32, f32) {
// We also roll the U/V_SCALE application into the final x and z formulas, // We also roll the U/V_SCALE application into the final x and z formulas,
// since some of that cancels out as well, and all of it can be avoided at // since some of that cancels out as well, and all of it can be avoided at
// runtime that way. // runtime that way.
const VU_RATIO: f32 = V_SCALE / U_SCALE;
let tmp = y / v; let tmp = y / v;
let x = tmp * ((2.25 * V_SCALE / U_SCALE) * u); // y * (9u / 4v) let x = tmp * ((2.25 * VU_RATIO) * u); // y * (9u / 4v)
let z = tmp * ((3.0 * V_SCALE) - ((0.75 * V_SCALE / U_SCALE) * u) - (5.0 * v)); // y * ((12 - 3u - 20v) / 4v) let z = tmp * ((3.0 * V_SCALE) - ((0.75 * VU_RATIO) * u) - (5.0 * v)); // y * ((12 - 3u - 20v) / 4v)
(x, y, z.max(0.0)) (x, y, z.max(0.0))
} }
@ -162,17 +154,17 @@ pub fn decode(fluv32: u32) -> (f32, f32, f32) {
/// to fit the range 0-255. /// to fit the range 0-255.
#[inline] #[inline]
pub fn decode_yuv(fluv32: u32) -> (f32, u8, u8) { pub fn decode_yuv(fluv32: u32) -> (f32, u8, u8) {
// Check for zero. const BIAS_OFFSET: u32 = (127 - EXP_BIAS as u32) << 23;
if fluv32 & 0xffff0000 == 0 {
return (0.0, (fluv32 >> 8) as u8, fluv32 as u8); let y = f32::from_bits(((fluv32 & 0xffff0000) >> 3) + BIAS_OFFSET);
let u = (fluv32 >> 8) as u8;
let v = fluv32 as u8;
if fluv32 <= 0xffff {
(0.0, u, v)
} else {
(y, u, v)
} }
// Calculate y.
let l_exp = fluv32 >> 26;
let l_mant = (fluv32 >> 16) & 0x3ff;
let y = f32::from_bits(((l_exp + 127 - EXP_BIAS as u32) << 23) | (l_mant << 13));
(y, (fluv32 >> 8) as u8, fluv32 as u8)
} }
#[cfg(test)] #[cfg(test)]