Extensions.cs

using System;
using Avalonia;
using Avalonia.Media;
using Avalonia.Media.Imaging;
using CSharpMath.Rendering.FrontEnd;
using AvaloniaColor = Avalonia.Media.Color;
using AvaloniaTextAlignment = Avalonia.Media.TextAlignment;
using CSharpMathTextAlignment = CSharpMath.Rendering.FrontEnd.TextAlignment;

namespace CSharpMath.Avalonia {
  public static class Extensions {
    public static AvaloniaColor ToAvaloniaColor(this System.Drawing.Color color) =>
        new AvaloniaColor(color.A, color.R, color.G, color.B);

    internal static System.Drawing.Color ToCSharpMathColor(this AvaloniaColor color) =>
        System.Drawing.Color.FromArgb(color.A, color.R, color.G, color.B);

    internal static CSharpMathTextAlignment ToCSharpMathTextAlignment(this AvaloniaTextAlignment alignment) =>
      alignment switch {
        AvaloniaTextAlignment.Left => CSharpMathTextAlignment.TopLeft,
        AvaloniaTextAlignment.Center => CSharpMathTextAlignment.Top,
        AvaloniaTextAlignment.Right => CSharpMathTextAlignment.TopRight,
        _ => CSharpMathTextAlignment.Left
      };

    public static SolidColorBrush ToSolidColorBrush(this System.Drawing.Color color) =>
        new SolidColorBrush(color.ToAvaloniaColor());

    public static void DrawAsPng<TContent>
      (this Painter<AvaloniaCanvas, TContent, AvaloniaColor> painter,
       System.IO.Stream target,
       float textPainterCanvasWidth = TextPainter.DefaultCanvasWidth,
       int? quality = null,
       CSharpMathTextAlignment alignmentForTests = CSharpMathTextAlignment.TopLeft) where TContent : class {
      if (!(painter.Measure(textPainterCanvasWidth) is { } size)) return;
      // RenderTargetBitmap does not support zero width/height. ArgumentException will be thrown.
      if (size.Width is 0) size.Width = 1;
      if (size.Height is 0) size.Height = 1;
      using var bitmap =
        new RenderTargetBitmap(new PixelSize((int)size.Width, (int)size.Height));
      using var context = bitmap.CreateDrawingContext();
      var canvas = new AvaloniaCanvas(context, new Size(size.Width, size.Height));
      painter.Draw(canvas, alignmentForTests);
      bitmap.Save(target, quality);
    }
  }
}