added comments for the WeakReference stuff

src/ImageSharp/Memory/ArrayPoolMemoryManager.Buffer{T}.cs

@@ -25,6 +25,10 @@ namespace SixLabors.ImageSharp.Memory
             /// <summary>
             /// A weak reference to the source pool.
             /// </summary>
+            /// <remarks>
+            /// By using a weak reference here, we are making sure that array pools and their retained arrays are always GC-ed
+            /// after a call to <see cref="ArrayPoolMemoryManager.ReleaseRetainedResources"/>, regardless of having buffer instances still being in use.
+            /// </remarks>
             private WeakReference<ArrayPool<byte>> sourcePoolReference;
 
             public Buffer(byte[] data, int length, ArrayPool<byte> sourcePool)

tests/ImageSharp.Tests/Memory/ArrayPoolMemoryManagerTests.cs

@@ -127,14 +127,21 @@ namespace SixLabors.ImageSharp.Tests.Memory
             }
         }
 
-        [Fact]
-        public void ReleaseRetainedResources_ReplacesInnerArrayPool()
+        [Theory]
+        [InlineData(false)]
+        [InlineData(true)]
+        public void ReleaseRetainedResources_ReplacesInnerArrayPool(bool keepBufferAlive)
         {
             IBuffer<int> buffer = this.MemoryManager.Allocate<int>(32);
             ref int ptrToPrev0 = ref buffer.Span.DangerousGetPinnableReference();
-            buffer.Dispose();
+
+            if (!keepBufferAlive)
+            {
+                buffer.Dispose();
+            }
 
             this.MemoryManager.ReleaseRetainedResources();
+            
             buffer = this.MemoryManager.Allocate<int>(32);
 
             Assert.False(Unsafe.AreSame(ref ptrToPrev0, ref buffer.DangerousGetPinnableReference()));

tests/ImageSharp.Tests/Memory/BufferAreaTests.cs

@@ -104,7 +104,7 @@ namespace SixLabors.ImageSharp.Tests.Memory
             {
                 BufferArea<int> area0 = buffer.GetArea(6, 8, 10, 10);
 
-                ref int r = ref area0.GetReferenceToOrigo();
+                ref int r = ref area0.GetReferenceToOrigin();
 
                 int expected = buffer[6, 8];
                 Assert.Equal(expected, r);