// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System;
using System.Numerics;
using System.Runtime.CompilerServices;

namespace SixLabors.ImageSharp.Drawing.Helpers {
  /// <summary>
  /// Provides helper methods for extracting properties from transformation matrices.
  /// </summary>
  internal static class MatrixUtilities
  {
      /// <summary>
      /// Extracts the average 2D scale factor from a <see cref="Matrix4x4"/>.
      /// This is the mean of the X and Y axis scale magnitudes, suitable for
      /// uniformly scaling radii under non-uniform or projective transforms.
      /// </summary>
      /// <param name="matrix">The transformation matrix.</param>
      /// <returns>The average scale factor.</returns>
      [MethodImpl(MethodImplOptions.AggressiveInlining)]
      public static float GetAverageScale(in Matrix4x4 matrix)
      {
          float sx = MathF.Sqrt((matrix.M11 * matrix.M11) + (matrix.M12 * matrix.M12));
          float sy = MathF.Sqrt((matrix.M21 * matrix.M21) + (matrix.M22 * matrix.M22));
          return (sx + sy) * 0.5f;
      }
  }
}