Add proper rounding compare

tests/ImageSharp.Tests/TestUtilities/FloatRoundingComparer.cs

@@ -0,0 +1,45 @@
+namespace ImageSharp.Tests.TestUtilities
+{
+    using System;
+    using System.Collections.Generic;
+
+    /// <summary>
+    /// Allows the comparison of single-precision floating point values by precision.
+    /// </summary>
+    public struct FloatRoundingComparer : IEqualityComparer<float>
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="FloatRoundingComparer"/> struct.
+        /// </summary>
+        /// <param name="precision">The number of decimal places (valid values: 0-7)</param>
+        public FloatRoundingComparer(int precision)
+        {
+            this.Precision = precision;
+        }
+
+        /// <summary>
+        /// Gets the number of decimal places (valid values: 0-7)
+        /// </summary>
+        public int Precision { get; }
+
+        /// <inheritdoc />
+        public bool Equals(float x, float y)
+        {
+            float xp = (float)Math.Round(x, this.Precision, MidpointRounding.AwayFromZero);
+            float yp = (float)Math.Round(y, this.Precision, MidpointRounding.AwayFromZero);
+
+            return Comparer<float>.Default.Compare(xp, yp) == 0;
+        }
+
+        /// <inheritdoc />
+        public int GetHashCode(float obj)
+        {
+            unchecked
+            {
+                int hashCode = obj.GetHashCode();
+                hashCode = (hashCode * 397) ^ this.Precision.GetHashCode();
+                return hashCode;
+            }
+        }
+    }
+}