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Contents
// Adapted from http://gimp.sourcearchive.com/documentation/2.6.6-1ubuntu1/color-to-alpha_8c-source.html
/*
toAlpha returns a color where the values of the argument have been converted to alpha
*/
ONECOLOR.installMethod('toAlpha', function (color) {
var me = this.rgb(),
other = ONECOLOR(color).rgb(),
epsilon = 1e-10,
a = new ONECOLOR.RGB(0, 0, 0, me._alpha),
channels = ['_red', '_green', '_blue'];
channels.forEach(function (channel) {
if (me[channel] < epsilon) {
a[channel] = me[channel];
} else if (me[channel] > other[channel]) {
a[channel] = (me[channel] - other[channel]) / (1 - other[channel]);
} else if (me[channel] > other[channel]) {
a[channel] = (other[channel] - me[channel]) / other[channel];
} else {
a[channel] = 0;
}
});
if (a._red > a._green) {
if (a._red > a._blue) {
me._alpha = a._red;
} else {
me._alpha = a._blue;
}
} else if (a._green > a._blue) {
me._alpha = a._green;
} else {
me._alpha = a._blue;
}
if (me._alpha < epsilon) {
return me;
}
channels.forEach(function (channel) {
me[channel] = (me[channel] - other[channel]) / me._alpha + other[channel];
});
me._alpha *= a._alpha;
return me;
});
Version data entries
2 entries across 2 versions & 1 rubygems