[Radiance-general] RGB to CIE-XYZ

[Nina Wittmann]

Thank you Raphael, but this is not the thing I wanted to know.

I would like to calculate XYZ from RGB with xyz_rgb.cal.

What I need are the commands that xyz_rgb.cal will calculate it.

rcalc ....

I hope anybody can help me.

Thanks, Nina



Raphael Compagnon schrieb:

> Sorry my previous answer was just irrelevant to your question...
> In fact you need the inverse transformation. Here it is:
>
> X=0.5142*r + 0.3240*g + 0.1618*b;
> Y=0.2652*r + 0.6702*g + 0.0646*b;
> Z=0.0240*r + 0.1229*g +  0.8531*b;
>
> x=X/(X+Y+Z);
> y=Y/(X+Y+Z);
> z=Z/(X+Y+Z);
>
> Hope this will help you.
>
> Raphaël
>
> At 28.06.2005 17:25, you wrote:
>
>> Hi all!
>>
>> I have a question about converting RGB to CIE-XYZ with xyz_rgb.cal.
>>
>> For transforming XYZ into RGB I can use this lines:
>>
>> rcalc -f xyz_rgb.cal  -e 'ix=$1;iy=$2;iY=$3'  -f xyz_rgb.cal \
>> -e 'iX=ix/iy*iY;iZ=(1-ix-iy)/iy*iY'  \
>> -e '$1=R(iX,iY,iZ) ; $2=G(iX,iY,iZ) ; $3=B(iX,iY,iZ)'
>>
>>
>> But there is also a part for calculating CIE-XYZ from RGB values, 
>> isn´t it?
>>
>> Unfortenatly, I don´t know what lines I have to write.
>>
>> Thanks,
>>
>> Nina
>>
>>
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>
>
>
>