Cleaned up some unused/commented code

- Small amount of refactoring
- Separated imagesharp extension to ImageSharpExtensions.cs
- Using .join Ienumerable extension instead of string.join in some places

src/NadekoBot/_Extensions/ImagesharpExtensions.cs

@@ -0,0 +1,98 @@
+using SixLabors.Fonts;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Drawing;
+using SixLabors.ImageSharp.Drawing.Processing;
+using SixLabors.ImageSharp.Formats;
+using SixLabors.ImageSharp.Formats.Png;
+using SixLabors.ImageSharp.PixelFormats;
+using SixLabors.ImageSharp.Processing;
+using Color = Discord.Color;
+
+namespace NadekoBot.Extensions;
+
+public static class ImagesharpExtensions
+{
+    /// <summary>
+    ///     Adds fallback fonts to <see cref="TextOptions" />
+    /// </summary>
+    /// <param name="opts"><see cref="TextOptions" /> to which fallback fonts will be added to</param>
+    /// <param name="fallback">List of fallback Font Families to add</param>
+    /// <returns>The same <see cref="TextOptions" /> to allow chaining</returns>
+    public static TextOptions WithFallbackFonts(this TextOptions opts, List<FontFamily> fallback)
+    {
+        foreach (var ff in fallback) opts.FallbackFonts.Add(ff);
+
+        return opts;
+    }
+
+    /// <summary>
+    ///     Adds fallback fonts to <see cref="TextGraphicsOptions" />
+    /// </summary>
+    /// <param name="opts"><see cref="TextGraphicsOptions" /> to which fallback fonts will be added to</param>
+    /// <param name="fallback">List of fallback Font Families to add</param>
+    /// <returns>The same <see cref="TextGraphicsOptions" /> to allow chaining</returns>
+    public static TextGraphicsOptions WithFallbackFonts(this TextGraphicsOptions opts, List<FontFamily> fallback)
+    {
+        opts.TextOptions.WithFallbackFonts(fallback);
+        return opts;
+    }
+    
+    // https://github.com/SixLabors/Samples/blob/master/ImageSharp/AvatarWithRoundedCorner/Program.cs
+    public static IImageProcessingContext ApplyRoundedCorners(this IImageProcessingContext ctx, float cornerRadius)
+    {
+        var size = ctx.GetCurrentSize();
+        var corners = BuildCorners(size.Width, size.Height, cornerRadius);
+
+        ctx.SetGraphicsOptions(new GraphicsOptions
+        {
+            Antialias = true,
+            // enforces that any part of this shape that has color is punched out of the background
+            AlphaCompositionMode = PixelAlphaCompositionMode.DestOut
+        });
+
+        foreach (var c in corners) ctx = ctx.Fill(SixLabors.ImageSharp.Color.Red, c);
+
+        return ctx;
+    }
+
+    private static IPathCollection BuildCorners(int imageWidth, int imageHeight, float cornerRadius)
+    {
+        // first create a square
+        var rect = new RectangularPolygon(-0.5f, -0.5f, cornerRadius, cornerRadius);
+
+        // then cut out of the square a circle so we are left with a corner
+        var cornerTopLeft = rect.Clip(new EllipsePolygon(cornerRadius - 0.5f, cornerRadius - 0.5f, cornerRadius));
+
+        // corner is now a corner shape positions top left
+        //lets make 3 more positioned correctly, we can do that by translating the original around the center of the image
+
+        var rightPos = imageWidth - cornerTopLeft.Bounds.Width + 1;
+        var bottomPos = imageHeight - cornerTopLeft.Bounds.Height + 1;
+
+        // move it across the width of the image - the width of the shape
+        var cornerTopRight = cornerTopLeft.RotateDegree(90).Translate(rightPos, 0);
+        var cornerBottomLeft = cornerTopLeft.RotateDegree(-90).Translate(0, bottomPos);
+        var cornerBottomRight = cornerTopLeft.RotateDegree(180).Translate(rightPos, bottomPos);
+
+        return new PathCollection(cornerTopLeft, cornerBottomLeft, cornerTopRight, cornerBottomRight);
+    }
+    
+    public static Color ToDiscordColor(this Rgba32 color)
+        => new(color.R, color.G, color.B);
+
+    public static MemoryStream ToStream(this Image<Rgba32> img, IImageFormat? format = null)
+    {
+        var imageStream = new MemoryStream();
+        if (format?.Name == "GIF")
+            img.SaveAsGif(imageStream);
+        else
+            img.SaveAsPng(imageStream,
+                new()
+                {
+                    ColorType = PngColorType.RgbWithAlpha, CompressionLevel = PngCompressionLevel.BestCompression
+                });
+
+        imageStream.Position = 0;
+        return imageStream;
+    }
+}