Created
November 25, 2015 05:35
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Conversion between RGB and LAB colorspace shader for Unity.
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#ifndef __LAB_COLORSPACE__ | |
#define __LAB_COLORSPACE__ | |
/* | |
* Conversion between RGB and LAB colorspace. | |
* Import from flowabs glsl program : https://code.google.com/p/flowabs/source/browse/glsl/?r=f36cbdcf7790a28d90f09e2cf89ec9a64911f138 | |
*/ | |
float3 rgb2xyz( float3 c ) { | |
float3 tmp; | |
tmp.x = ( c.r > 0.04045 ) ? pow( ( c.r + 0.055 ) / 1.055, 2.4 ) : c.r / 12.92; | |
tmp.y = ( c.g > 0.04045 ) ? pow( ( c.g + 0.055 ) / 1.055, 2.4 ) : c.g / 12.92, | |
tmp.z = ( c.b > 0.04045 ) ? pow( ( c.b + 0.055 ) / 1.055, 2.4 ) : c.b / 12.92; | |
const float3x3 mat = float3x3( | |
0.4124, 0.3576, 0.1805, | |
0.2126, 0.7152, 0.0722, | |
0.0193, 0.1192, 0.9505 | |
); | |
return 100.0 * mul(tmp, mat); | |
} | |
float3 xyz2lab( float3 c ) { | |
float3 n = c / float3(95.047, 100, 108.883); | |
float3 v; | |
v.x = ( n.x > 0.008856 ) ? pow( n.x, 1.0 / 3.0 ) : ( 7.787 * n.x ) + ( 16.0 / 116.0 ); | |
v.y = ( n.y > 0.008856 ) ? pow( n.y, 1.0 / 3.0 ) : ( 7.787 * n.y ) + ( 16.0 / 116.0 ); | |
v.z = ( n.z > 0.008856 ) ? pow( n.z, 1.0 / 3.0 ) : ( 7.787 * n.z ) + ( 16.0 / 116.0 ); | |
return float3(( 116.0 * v.y ) - 16.0, 500.0 * ( v.x - v.y ), 200.0 * ( v.y - v.z )); | |
} | |
float3 rgb2lab( float3 c ) { | |
float3 lab = xyz2lab( rgb2xyz( c ) ); | |
return float3( lab.x / 100.0, 0.5 + 0.5 * ( lab.y / 127.0 ), 0.5 + 0.5 * ( lab.z / 127.0 )); | |
} | |
float3 lab2xyz( float3 c ) { | |
float fy = ( c.x + 16.0 ) / 116.0; | |
float fx = c.y / 500.0 + fy; | |
float fz = fy - c.z / 200.0; | |
return float3( | |
95.047 * (( fx > 0.206897 ) ? fx * fx * fx : ( fx - 16.0 / 116.0 ) / 7.787), | |
100.000 * (( fy > 0.206897 ) ? fy * fy * fy : ( fy - 16.0 / 116.0 ) / 7.787), | |
108.883 * (( fz > 0.206897 ) ? fz * fz * fz : ( fz - 16.0 / 116.0 ) / 7.787) | |
); | |
} | |
float3 xyz2rgb( float3 c ) { | |
const float3x3 mat = float3x3( | |
3.2406, -1.5372, -0.4986, | |
-0.9689, 1.8758, 0.0415, | |
0.0557, -0.2040, 1.0570 | |
); | |
float3 v = mul(c / 100.0, mat); | |
float3 r; | |
r.x = ( v.r > 0.0031308 ) ? (( 1.055 * pow( v.r, ( 1.0 / 2.4 ))) - 0.055 ) : 12.92 * v.r; | |
r.y = ( v.g > 0.0031308 ) ? (( 1.055 * pow( v.g, ( 1.0 / 2.4 ))) - 0.055 ) : 12.92 * v.g; | |
r.z = ( v.b > 0.0031308 ) ? (( 1.055 * pow( v.b, ( 1.0 / 2.4 ))) - 0.055 ) : 12.92 * v.b; | |
return r; | |
} | |
float3 lab2rgb( float3 c ) { | |
return xyz2rgb( lab2xyz( float3(100.0 * c.x, 2.0 * 127.0 * (c.y - 0.5), 2.0 * 127.0 * (c.z - 0.5)) ) ); | |
} | |
#endif |
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In lab2rgb function why do you change the color given to lab2xyz as float3(100.0 * c.x, 2.0 * 127.0 * (c.y - 0.5), 2.0 * 127.0 * (c.z - 0.5))?
why not just xyz2rgb( lab2xyz( c));?