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var utils = require('../utils')
, nodes = require('../nodes');
/**
* Blend the `top` color over the `bottom`
*
* Examples:
*
* blend(rgba(#FFF, 0.5), #000)
* // => #808080
*
* blend(rgba(#FFDE00,.42), #19C261)
* // => #7ace38
*
* blend(rgba(lime, 0.5), rgba(red, 0.25))
* // => rgba(128,128,0,0.625)
*
* @param {RGBA|HSLA} top
* @param {RGBA|HSLA} [bottom=#fff]
* @return {RGBA}
* @api public
*/
module.exports = function blend(top, bottom){
// TODO: different blend modes like overlay etc.
utils.assertColor(top);
top = top.rgba;
bottom = bottom || new nodes.RGBA(255, 255, 255, 1);
utils.assertColor(bottom);
bottom = bottom.rgba;
return new nodes.RGBA(
top.r * top.a + bottom.r * (1 - top.a),
top.g * top.a + bottom.g * (1 - top.a),
top.b * top.a + bottom.b * (1 - top.a),
top.a + bottom.a - top.a * bottom.a);
};
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