2019-11-29-win10-uwp-颜色转换

title	author	date	CreateTime	categories
win10 uwp 颜色转换	lindexi	2019-11-29 10:18:27 +0800	2018-2-13 17:23:3 +0800	Win10 UWP

本文告诉大家如何从字符串转颜色，从颜色转字符串

字符串转颜色

在 WPF 可以使用下面的代码把十六进制的颜色字符串转颜色

            Color color = (Color) ColorConverter.ConvertFromString("#FFDFD991");

string hex = "#FFFFFF";  
Color color = System.Drawing.ColorTranslator.FromHtml(hex);

但是 UWP 没这个方法，所以需要自己写一个方法

        public SolidColorBrush GetSolidColorBrush(string hex)
        {
            hex = hex.Replace("#", string.Empty);
            byte a = (byte) (Convert.ToUInt32(hex.Substring(0, 2), 16));
            byte r = (byte) (Convert.ToUInt32(hex.Substring(2, 2), 16));
            byte g = (byte) (Convert.ToUInt32(hex.Substring(4, 2), 16));
            byte b = (byte) (Convert.ToUInt32(hex.Substring(6, 2), 16));
            return new SolidColorBrush(Windows.UI.Color.FromArgb(a, r, g, b));
        }

如果有小伙伴传入一个不带透明的，那么上面的代码就会出现异常，因为不带透明的颜色只有 6 个字符，所以就无法使用上面的代码，我修改了下面代码可以转换颜色

       public SolidColorBrush GetSolidColorBrush(string hex)
        {
            hex = hex.Replace("#", string.Empty);

            bool existAlpha = hex.Length == 8;

            if (!existAlpha && hex.Length != 6)
            {
                throw new ArgumentException("输入的hex不是有效颜色");
            }

            int n = 0;
            byte a;
            if (existAlpha)
            {
                n = 2;
                a = (byte) ConvertHexToByte(hex, 0);
            }
            else
            {
                a = 0xFF;
            }

            var r = (byte) ConvertHexToByte(hex, n);
            var g = (byte) ConvertHexToByte(hex, n + 2);
            var b = (byte) ConvertHexToByte(hex, n + 4);
            return new SolidColorBrush(Windows.UI.Color.FromArgb(a, r, g, b));
        }

        private static uint ConvertHexToByte(string hex, int n)
        {
            return Convert.ToUInt32(hex.Substring(n, 2), 16);
        }

大家可以从上面代码发现 ConvertHexToByte 这就是 16 进制转 int 的方法，请看C# 16 进制字符串转 int

但是存在这样写的颜色 #FD92 #DAC 的颜色，所以还需要继续修改一下算法

       public SolidColorBrush GetSolidColorBrush(string hex)
        {
            hex = hex.Replace("#", string.Empty);

            //#FFDFD991
            //#DFD991
            //#FD92
            //#DAC

            bool existAlpha = hex.Length == 8 || hex.Length == 4;
            bool isDoubleHex = hex.Length == 8 || hex.Length == 6;

            if (!existAlpha && hex.Length != 6 && hex.Length != 3)
            {
                throw new ArgumentException("输入的hex不是有效颜色");
            }

            int n = 0;
            byte a;
            int hexCount = isDoubleHex ? 2 : 1;
            if (existAlpha)
            {
                n = hexCount;
                a = (byte) ConvertHexToByte(hex, 0, hexCount);
                if (!isDoubleHex)
                {
                    a = (byte) (a * 16 + a);
                }
            }
            else
            {
                a = 0xFF;
            }

            var r = (byte) ConvertHexToByte(hex, n, hexCount);
            var g = (byte) ConvertHexToByte(hex, n + hexCount, hexCount);
            var b = (byte) ConvertHexToByte(hex, n + 2 * hexCount, hexCount);
            if (!isDoubleHex)
            {
                //#FD92 = #FFDD9922

                r = (byte) (r * 16 + r);
                g = (byte) (g * 16 + g);
                b = (byte) (b * 16 + b);
            }

            return new SolidColorBrush(Windows.UI.Color.FromArgb(a, r, g, b));
        }

        private static uint ConvertHexToByte(string hex, int n, int count = 2)
        {
            return Convert.ToUInt32(hex.Substring(n, count), 16);
        }