LYGIA Shader Library

Use:

<vec3\vec4> oklab2srgb(<vec3|vec4> oklab)

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#ifndef MAT_OKLAB2SRGB
#define MAT_OKLAB2SRGB
const mat3 OKLAB2SRGB_A = mat3(  
    1.0,            1.0,            1.0,
    0.3963377774,  -0.1055613458,  -0.0894841775,
    0.2158037573,  -0.0638541728,  -1.2914855480);

const mat3 OKLAB2SRGB_B = mat3(  
    4.0767245293,  -1.2681437731,   -0.0041119885,
    -3.3072168827,  2.3098,          0.2307590544, 
    -0.3411344290,  1.7066093323231,-0.7034768625689);
#endif

#ifndef FNC_OKLAB2SRGB
#define FNC_OKLAB2SRGB
vec3 oklab2srgb(const in vec3 oklab) { 
    vec3 lms = OKLAB2SRGB_A * oklab;
    return OKLAB2SRGB_B * (lms * lms * lms);
}
vec4 oklab2srgb(const in vec4 oklab) { return vec4(oklab2srgb(oklab.xyz), oklab.a); }
#endif

Use:

<float3\float4> oklab2srgb(<float3|float4> oklab)

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#ifndef MAT_OKLAB2SRGB
#define MAT_OKLAB2SRGB
const float3x3 OKLAB2SRGB_A = float3x3(  
    1.0,            1.0,            1.0,
    0.3963377774,  -0.1055613458,  -0.0894841775,
    0.2158037573,  -0.0638541728,  -1.2914855480);

const float3x3 OKLAB2SRGB_B = float3x3(  
    4.0767245293,  -1.2681437731,   -0.0041119885,
    -3.3072168827,  2.3098,          0.2307590544, 
    -0.3411344290,  1.7066093323231,-0.7034768625689);
#endif

#ifndef FNC_OKLAB2SRGB
#define FNC_OKLAB2SRGB
float3 oklab2srgb(float3 oklab) {
    float3 lms = mul(OKLAB2SRGB_A, oklab);
    return mul(OKLAB2SRGB_B, (lms * lms * lms));
}
float4 oklab2srgb(float4 oklab) { return float4(oklab2srgb(oklab.xyz), oklab.a); }
#endif

Check it on Github

const OKLAB2SRGB_A : mat3x3<f32>  = mat3x3<f32>( 
    vec3f(1.0, 1.0, 1.0), 
    vec3f(0.3963377774, -0.1055613458, -0.0894841775), 
    vec3f(0.2158037573, -0.0638541728, -1.2914855480) );

const OKLAB2SRGB_B : mat3x3<f32>  = mat3x3<f32>( 
    vec3f(4.0767245293, -1.2681437731, -0.0041119885), 
    vec3f(-3.3072168827, 2.3098, 0.2307590544), 
    vec3f(-0.3411344290,  1.7066093323231, -0.7034768625689) );

fn oklab2srgb(oklab: vec3f) -> vec3f {
    let lms = OKLAB2SRGB_A * oklab;
    return OKLAB2SRGB_B * (lms * lms * lms);
}