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