RGBtoHSL ( redPercentage ; greenPercentage ; bluePercentage )

Converts color from RGB percentages to HSL values.

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Joe Rovang - Show more from this author

Sample input:

RGBtoHSL ( 1; 0; 0 ) // red

Sample output:

0¶
1¶
.5

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

If ( ( redPercentage = greenPercentage ) and ( greenPercentage = bluePercentage ); List ( 0; 0; redPercentage );

Let (

[

r = redPercentage;
g = greenPercentage;
b = bluePercentage;

maxC = Max ( r; g; b );
minC = Min ( r; g; b );

sumC = maxC + minC;
diffC = maxC - minC;

li = sumC / 2;

s = If ( li < .5;
	diffC / sumC;
	diffC / ( 2 - sumC )
);

hRaw = Case (
	( maxC = r ); ( g - b ) / diffC;
	( maxC = g ); 2 + ( ( b - r ) / diffC );
	4 + ( ( r - g ) / diffC )
);
h = hRaw/6 + ( hRaw < 0 )

];

List ( h; s; li )

) // end Let
) // end If

This function converts the specified color RGB percentages to hue, saturation, and lightness (HSL) values. (Note that HSL is not the same as HSB/HSV!)

All values except hue are in decimals between 0 and 1, inclusively. RGB values on the 0-255 scale must be divided by 255 before using them in this function.

Comments

		Alexander Zueiv, Tashkent Oct 20, 2012
The example RGBtoHSL ( 1; 0; 0 ) returns "0Â¶?Â¶1". The mistake is probably in the line 14: sumC = maxC + maxC; It should probably be: sumC = maxC + minC; Is that correct?

		Joe Rovang Oct 20, 2012
Yes, thanks, careless translation from Java. Edited.

Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

RGBtoHSL ( redPercentage ; greenPercentage ; bluePercentage )

Comments

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