Hi,
I have some questions about delta E calculation.
I calculated the delta E between this lab points:
L = 54.44073903
a = -34.82222743
b = 0.18986800
L = 54.92340686
a = -33.45703125
b = 0.00000000
using several formulas obtaing this values:
cmsDeltaE = 1.460
cmsCIE94DeltaE = 0.719
cmsCMCdeltaE = 0.769
deltaCIE00( 1.0, 1.0, 1.0 ) = 52.908
Is it right deltaCIE00 produces a so big value?
I tried a debug using the following spreadsheet and related article
http://www.ece.rochester.edu/~gsharma/ciede2000/dataNprograms/CIEDE2000.xls
http://www.ece.rochester.edu/~gsharma/ciede2000/ciede2000noteCRNA.pdf
and I found a possible cause in the line
double h_ps = atan2deg(a_ps, b_ps);
This function should return 180 and return 0 instead.
If I modify the function in this way
static
double atan2deg(double b, double a)
{
double h;
/*if (a == 0)
h = 0;
else*/
h = atan2(a, b);
h *= (180. / M_PI);
while (h > 360.)
h -= 360.;
while ( h < 0)
h += 360.;
return h;
}
I obtain a value 0.72243850693447653.
Is it correct?
Can I have your opinion about this modification?
Is there a way to speficy parameters in cmsCIE94DeltaE and
cmsCMCdeltaE similarly to deltaCIE00?
Regards,
Andrea
--
Andrea Galligani __\/__
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