Revert "Remove export code as it's not needed"

This reverts commit 8bab9abbf5da3c196078f66b49f401cf84a324db.

src/PixiEditor/Models/IO/PaletteParsers/CorelDrawPalParser.cs

@@ -10,6 +10,9 @@ internal class CorelDrawPalParser : PaletteFileParser
     public override string FileName { get; } = "CorelDRAW! 3.0 Palette";
     public override string[] SupportedFileExtensions { get; } = { ".pal" };
 
+    // Default name to use for colors (color name is required by format)
+    private const string SWATCH_NAME = "PixiEditor Color";
+
     public override async Task<PaletteFileData> Parse(string path)
     {
         try
@@ -69,9 +72,51 @@ internal class CorelDrawPalParser : PaletteFileParser
 
     public override bool CanSave => false;
 
+    // NOTE: saving data works but PixiEditor defaults to first .pal parser which
+    //       is JASC so saving to an actual file is currently not available.
+    //       Palette exporter needs to be refactored to support multiple formats of
+    //       same file extension.
     public override async Task<bool> Save(string path, PaletteFileData data)
     {
-        throw new SavingNotSupportedException("Saving palette as CorelDRAW! 3.0 palette directly is not supported.");
+        StringBuilder sb = new StringBuilder(SWATCH_NAME.Length + 20);
+
+        try
+        {
+            await using (Stream stream = File.OpenWrite(path))
+            {
+                using (TextWriter writer = new StreamWriter(stream, Encoding.ASCII, 1024, true))
+                {
+                    foreach (var color in data.Colors)
+                    {
+                        this.ConvertRgbToCmyk(color, out byte c, out byte m, out byte y, out byte k);
+
+                        this.WriteName(sb, SWATCH_NAME);
+                        this.WriteNumber(sb, c);
+                        this.WriteNumber(sb, m);
+                        this.WriteNumber(sb, y);
+                        this.WriteNumber(sb, k);
+
+                        writer.WriteLine(sb.ToString());
+                        sb.Length = 0;
+                    }
+                }
+            }
+            return true;
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    private static byte ClampCmyk(float value)
+    {
+        if (value < 0 || float.IsNaN(value))
+        {
+            value = 0;
+        }
+
+        return Convert.ToByte(value * 100);
     }
 
     private PaletteColor ConvertCmykToRgb(int c, int m, int y, int k)
@@ -88,6 +133,23 @@ internal class CorelDrawPalParser : PaletteFileParser
         return new PaletteColor((byte)r, (byte)g, (byte)b);
     }
 
+    private void ConvertRgbToCmyk(PaletteColor color, out byte c, out byte m, out byte y, out byte k)
+    {
+        float r, g, b;
+        float divisor;
+
+        r = color.R / 255F;
+        g = color.G / 255F;
+        b = color.B / 255F;
+
+        divisor = 1 - Math.Max(Math.Max(r, g), b);
+
+        c = ClampCmyk((1 - r - divisor) / (1 - divisor));
+        m = ClampCmyk((1 - g - divisor) / (1 - divisor));
+        y = ClampCmyk((1 - b - divisor) / (1 - divisor));
+        k = ClampCmyk(divisor);
+    }
+
     private byte NextNumber(string line, ref int start)
     {
         int length;
@@ -123,4 +185,36 @@ internal class CorelDrawPalParser : PaletteFileParser
 
         return result;
     }
+
+    private void WriteName(StringBuilder sb, string name)
+    {
+        sb.Append('"');
+        sb.Append(name);
+        sb.Append('"');
+
+        for (int j = (name ?? string.Empty).Length; j < name.Length; j++)
+        {
+            sb.Append(' ');
+        }
+    }
+
+    private void WriteNumber(StringBuilder sb, byte value)
+    {
+        if (value == 100)
+        {
+            sb.Append("100 ");
+        }
+        else
+        {
+            sb.Append(' ');
+            if (value < 10)
+            {
+                sb.Append(' ');
+            }
+
+            sb.Append(value);
+
+            sb.Append(' ');
+        }
+    }
 }