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November 23, 2023 04:14
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判断颜色是深色还是浅色 可以用来做背景色检测, 决定前景色(文字等)应该用浅色还是深色
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| const REG_HEX = /(^#?[0-9A-F]{6}$)|(^#?[0-9A-F]{3}$)/i; | |
| /* | |
| * rgb字符串解析 | |
| * accepts: #333 #accded (without # is also fine) | |
| * not accept yet: rgb(), rgba() | |
| */ | |
| function parseRGB(str){ | |
| if(typeof str === 'string' && REG_HEX.test(str) ){ | |
| str = str.replace('#', ''); | |
| let arr; | |
| if(str.length === 3){ | |
| arr = str.split('').map(c => (c+c)); | |
| } | |
| else if(str.length === 6){ | |
| arr = str.match(/[a-zA-Z0-9]{2}/g); | |
| } | |
| else{ | |
| throw new Error('wrong color format'); | |
| } | |
| return arr.map((c) => parseInt(c, 16)); | |
| } | |
| throw new Error('color should be string'); | |
| } | |
| /* | |
| * rgb value to hsl 色相(H)、饱和度(S)、明度(L) | |
| */ | |
| function rgbToHsl(rgbStr){ | |
| let [r, g, b] = parseRGB(rgbStr); | |
| r /= 255, g /= 255, b /= 255; | |
| let max = Math.max(r, g, b), min = Math.min(r, g, b); | |
| let h, s, l = (max + min) / 2; | |
| if(max == min){ | |
| h = s = 0; // achromatic | |
| }else{ | |
| let d = max - min; | |
| s = l > 0.5 ? d / (2 - max - min) : d / (max + min); | |
| switch(max){ | |
| case r: h = (g - b) / d + (g < b ? 6 : 0); break; | |
| case g: h = (b - r) / d + 2; break; | |
| case b: h = (r - g) / d + 4; break; | |
| } | |
| h /= 6; | |
| } | |
| return [h, s, l]; | |
| } | |
| /* | |
| * 判断颜色属于深色还是浅色 | |
| */ | |
| function isColorDarkOrLight(rgbStr){ | |
| let [h, s, l] = rgbToHsl(rgbStr); | |
| return (l > 0.5)? 'light' : 'dark'; | |
| } |
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为啥不考虑透明度呢