Matrix Multiplikation to convert RGB to XYZ

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raphealra..

Matrix Multiplikation to convert RGB to XYZ

in Programming Questions • 1 year ago

Hello Together

I have a color sensor that sends me its values over a PIC32 over RS 232 to processing.
Well, I have to transform the ADC measurements into the color space.

Well for that I need a matrix multiplication:

|Radc|    |3.037;   -1.25 ; 0.239|    |x|
|Gadc| x |0.42 ;   2.325; -1.244| =|y|
|Badc|    |-0.689; 0.20 ; 7.45 |    |z|

Is there a good libray maybe from rotating cubes (ore some 3D libs) I can make a quicke step ?

What cool someone can help me with the matrix stuff

Thx in advance
Raph

Replies(3)

allonestr..

Re: Matrix Multiplikation to convert RGB to XYZ

1 year ago

I have a function convertRGBoXYZ which is as follows, where redbit, greenbit and bluebit are the respective RGB components. Note that I've included an address to the website where I found the values to use.

//conversion matrix from http://www.brucelindbloom.com/index.html?Eqn_RGB_to_XYZ.html
XYZcolour convertRGBtoXYZ()
{
    float xbit = (0.6326696 * redbit + 0.2045558 * greenbit + 0.1269946 * bluebit);
    float ybit = (0.2284569 * redbit + 0.7373523 * greenbit + 0.0341908 * bluebit);
    float zbit = (0 * redbit + 0.0095142 * greenbit + 0.8156958 * bluebit);

    return new XYZcolour(xbit/255, ybit/255, zbit/255);
}

raphealra..

Re: Re: Matrix Multiplikation to convert RGB to XYZ

1 year ago

Cool works fine... I used the special matrix parameter from my color sensor

dr.mo

Re: Matrix Multiplikation to convert RGB to XYZ

1 year ago

if those values are fixed why not do it by hand? simple matrix multiplication of 1x3 times 3x4 ( http://en.wikipedia.org/wiki/Matrix_multiplication ):

                           |3.037 -1.25 0.239|
|Radc Gadc Badc|   x |0.42 2.325 -1.244| =|x y z|
                           |-0.689 0.20 7.45 |

==>

x = Radc * 3.037 + Gadc * 0.42 - Badc * 0.689;

y = -Radc * 1.25 + Gadc * 2.325 + Badc * 0.2;

z = Radc * 0.239 - Gadc * 1.244 + Badc * 7.45;

(disclaimer - please double check this)

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