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@kozo002
Created October 3, 2013 07:38
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Get brightness from background color with jQuery
jQuery.fn.brightness = function() {
var bg_color, rgba, y;
bg_color = this.css('background-color');
if ((bg_color != null) && bg_color.length) {
rgba = bg_color.match(/^rgb(?:a)?\(([0-9]{1,3}),\s([0-9]{1,3}),\s([0-9]{1,3})(?:,\s)?([0-9]{1,3})?\)$/);
if (rgba != null) {
if (rgba[4] === '0') {
if (this.parent().length) return this.parent().brightness();
} else {
y = 2.99 * rgba[1] + 5.87 * rgba[2] + 1.14 * rgba[3];
if (y >= 1275) {
return 'light';
} else {
return 'dark';
}
}
}
} else {
if (this.parent().length) return this.parent().brightness();
}
};
@xem
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xem commented Oct 8, 2013

Where do the numbers come from?

@OwlyCode
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OwlyCode commented Oct 8, 2013

Even its not the exact values it might be related to this http://en.wikipedia.org/wiki/Luminance_(relative). The general idea is that green impacts us the most on the perception of what is "bright".

@wooorm
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wooorm commented Oct 8, 2013

The Y in YIQ.

@ezebra
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ezebra commented Apr 26, 2017

Hi, may I use this gist in a project? I couldn't find any licensing information.

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