Added a dark mode

Author: borisonekenobi

.vs/imageResizer/v17/.suo

@@ -1,33 +1,130 @@
-using System;
+using Microsoft.Win32;
+using System;
+using System.Drawing;
+using System.Globalization;
+using System.Runtime.InteropServices;
 using System.Windows.Forms;
 
 namespace imageResizer
 {
     public partial class AboutBox : Form
     {
+        internal Options Options {  get; set; }
+
         public AboutBox()
         {
             InitializeComponent();
         }
 
-        private void buttonOK_Click(object sender, EventArgs e)
+        private void ButtonOK_Click(object sender, EventArgs e)
         {
             this.Close();
         }
 
-        private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
+        private void LinkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
         {
             System.Diagnostics.Process.Start("https://github.com/borisonekenobi/");
         }
 
-        private void linkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
+        private void LinkLabel2_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
         {
             System.Diagnostics.Process.Start("mailto:borisonekenobi@gmail.com");
         }
 
         private void AboutBox_Load(object sender, EventArgs e)
         {
+            UpdateTheme();
             label5.Text = "Current: v" + Form1.CurrentVersion + "\nLatest: v" + Form1.LatestVersion;
         }
+
+        private void UpdateTheme()
+        {
+            if (Options.Theme == 0)
+            {
+                SetLightTheme();
+            }
+            else if (Options.Theme == 1)
+            {
+                SetDarkTheme();
+            }
+            else
+            {
+                if (UsingLightTheme())
+                {
+                    SetLightTheme();
+                }
+                else
+                {
+                    SetDarkTheme();
+                }
+            }
+        }
+
+        private void SetLightTheme()
+        {
+            BackColor = DefaultBackColor;
+            ForeColor = DefaultForeColor;
+
+            buttonOK.BackColor = DefaultBackColor;
+            buttonOK.FlatAppearance.BorderSize = 1;
+        }
+
+        private void SetDarkTheme()
+        {
+            BackColor = backgroundColor;
+            ForeColor = foregroundColor;
+
+            buttonOK.BackColor = buttonColor;
+            buttonOK.FlatAppearance.BorderSize = buttonBorderSize;
+        }
+
+        private static bool UsingLightTheme()
+        {
+            var registryKey = Registry.CurrentUser.OpenSubKey(@"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize");
+            var appsUseLightTheme = registryKey?.GetValue("AppsUseLightTheme");
+
+            if (appsUseLightTheme is null)
+            {
+                return true;
+            }
+            else
+            {
+                return Convert.ToBoolean(appsUseLightTheme, CultureInfo.InvariantCulture);
+            }
+        }
+
+        [DllImport("dwmapi.dll")]
+        private static extern int DwmSetWindowAttribute(IntPtr hwnd, int attr, ref int attrValue, int attrSize);
+
+        private const int DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1 = 19;
+        private const int DWMWA_USE_IMMERSIVE_DARK_MODE = 20;
+
+        internal static bool UseImmersiveDarkMode(IntPtr handle, bool enabled)
+        {
+            if (IsWindows10OrGreater(17763))
+            {
+                var attribute = DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1;
+                if (IsWindows10OrGreater(18985))
+                {
+                    attribute = DWMWA_USE_IMMERSIVE_DARK_MODE;
+                }
+
+                int useImmersiveDarkMode = enabled ? 1 : 0;
+                return DwmSetWindowAttribute(handle, (int)attribute, ref useImmersiveDarkMode, sizeof(int)) == 0;
+            }
+
+            return false;
+        }
+
+        private static bool IsWindows10OrGreater(int build = -1)
+        {
+            return Environment.OSVersion.Version.Major >= 10 && Environment.OSVersion.Version.Build >= build;
+        }
+
+        // styles for dark mode
+        Color backgroundColor = Color.FromArgb(12, 12, 12);
+        Color foregroundColor = Color.White;
+        Color buttonColor = Color.FromArgb(44, 44, 44);
+        int buttonBorderSize = 0;
     }
 }