30 lines
940 B
TypeScript
30 lines
940 B
TypeScript
import { TinyColor } from '@ctrl/tinycolor';
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function isStableColor(color: number): boolean {
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return color >= 0 && color <= 255;
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}
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function getAlphaColor(frontColor: string, backgroundColor: string): string {
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const { r: fR, g: fG, b: fB, a: originAlpha } = new TinyColor(frontColor).toRgb();
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if (originAlpha < 1) {
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return frontColor;
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}
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const { r: bR, g: bG, b: bB } = new TinyColor(backgroundColor).toRgb();
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for (let fA = 0.01; fA <= 1; fA += 0.01) {
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const r = Math.round((fR - bR * (1 - fA)) / fA);
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const g = Math.round((fG - bG * (1 - fA)) / fA);
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const b = Math.round((fB - bB * (1 - fA)) / fA);
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if (isStableColor(r) && isStableColor(g) && isStableColor(b)) {
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return new TinyColor({ r, g, b, a: Math.round(fA * 100) / 100 }).toRgbString();
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}
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}
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// fallback
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/* istanbul ignore next */
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return new TinyColor({ r: fR, g: fG, b: fB, a: 1 }).toRgbString();
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}
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export default getAlphaColor;
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