Implemented dispose method according to common convention.

src/ImageSharp/Image.cs

@@ -87,7 +87,8 @@ namespace SixLabors.ImageSharp
                 return;
             }
 
-            this.DisposeManaged();
+            this.Dispose(true);
+            GC.SuppressFinalize(this);
 
             this.isDisposed = true;
         }
@@ -150,7 +151,8 @@ namespace SixLabors.ImageSharp
         /// <summary>
         /// Internal routine for freeing managed resources called from <see cref="Dispose"/>
         /// </summary>
-        protected abstract void DisposeManaged();
+        /// /// <param name="disposing">Whether to dispose of managed objects.</param>
+        protected abstract void Dispose(bool disposing);
 
         /// <summary>
         /// Throws <see cref="ObjectDisposedException"/> if the image is disposed.

src/ImageSharp/ImageFrameCollection.cs

@@ -174,7 +174,8 @@ namespace SixLabors.ImageSharp
                 return;
             }
 
-            this.DisposeManaged();
+            this.Dispose(true);
+            GC.SuppressFinalize(this);
 
             this.isDisposed = true;
         }
@@ -204,7 +205,8 @@ namespace SixLabors.ImageSharp
         /// <summary>
         /// Internal routine for freeing managed resources called from <see cref="Dispose"/>
         /// </summary>
-        protected abstract void DisposeManaged();
+        /// /// /// <param name="disposing">Whether to dispose of managed objects.</param>
+        protected abstract void Dispose(bool disposing);
 
         /// <summary>
         /// Implements <see cref="GetEnumerator"/>.

src/ImageSharp/ImageFrameCollection{TPixel}.cs

@@ -396,14 +396,17 @@ namespace SixLabors.ImageSharp
         }
 
         /// <inheritdoc/>
-        protected override void DisposeManaged()
+        protected override void Dispose(bool disposing)
         {
-            foreach (ImageFrame<TPixel> f in this.frames)
+            if (disposing)
             {
-                f.Dispose();
-            }
+                foreach (ImageFrame<TPixel> f in this.frames)
+                {
+                    f.Dispose();
+                }
 
-            this.frames.Clear();
+                this.frames.Clear();
+            }
         }
 
         private ImageFrame<TPixel> CopyNonCompatibleFrame(ImageFrame source)

src/ImageSharp/Image{TPixel}.cs

@@ -268,7 +268,13 @@ namespace SixLabors.ImageSharp
         }
 
         /// <inheritdoc/>
-        protected override void DisposeManaged() => this.frames.Dispose();
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                this.frames.Dispose();
+            }
+        }
 
         /// <inheritdoc/>
         public override string ToString() => $"Image<{typeof(TPixel).Name}>: {this.Width}x{this.Height}";