introduce IImageFrameCollectino to hide disposable

src/ImageSharp/Image/IImageFrameCollection.cs

@@ -0,0 +1,84 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace SixLabors.ImageSharp
+{
+    /// <summary>
+    /// Encapsulates an imaged collection of frames.
+    /// </summary>
+    /// <typeparam name="TPixel">The type of the pixel.</typeparam>
+    public interface IImageFrameCollection<TPixel> : IEnumerable<ImageFrame<TPixel>>
+        where TPixel : struct, IPixel<TPixel>
+    {
+        /// <summary>
+        /// Gets the count.
+        /// </summary>
+        int Count { get; }
+
+        /// <summary>
+        /// Gets the root frame.
+        /// </summary>
+        ImageFrame<TPixel> RootFrame { get; }
+
+        /// <summary>
+        /// Gets or sets the <see cref="ImageFrame{TPixel}"/> at the specified index.
+        /// </summary>
+        /// <value>
+        /// The <see cref="ImageFrame{TPixel}"/>.
+        /// </value>
+        /// <param name="index">The index.</param>
+        /// <returns>The <see cref="ImageFrame{TPixel}"/> at the specified index.</returns>
+        ImageFrame<TPixel> this[int index] { get; set; }
+
+        /// <summary>
+        ///  Determines the index of a specific <paramref name="frame"/> in the <seealso cref="Image{TPixel}"/>.
+        /// </summary>
+        /// <param name="frame">The <seealso cref="ImageFrame{TPixel}"/> to locate in the <seealso cref="Image{TPixel}"/>.</param>
+        /// <returns>The index of item if found in the list; otherwise, -1.</returns>
+        int IndexOf(ImageFrame<TPixel> frame);
+
+        /// <summary>
+        ///  Inserts the <paramref name="frame"/> to the <seealso cref="Image{TPixel}"/> at the specified <paramref name="index"/>.
+        /// </summary>
+        /// <param name="index"> The zero-based index at which item should be inserted..</param>
+        /// <param name="frame">The <seealso cref="ImageFrame{TPixel}"/> to insert into the <seealso cref="Image{TPixel}"/>.</param>
+        void Insert(int index, ImageFrame<TPixel> frame);
+
+        /// <summary>
+        /// Removes the <seealso cref="ImageFrame{TPixel}"/> from the <seealso cref="Image{TPixel}"/> at the specified index.
+        /// </summary>
+        /// <param name="index">The zero-based index of the item to remove.</param>
+        /// <exception cref="InvalidOperationException">Cannot remove last frame.</exception>
+        void RemoveAt(int index);
+
+        /// <summary>
+        /// Adds the specified frame.
+        /// </summary>
+        /// <param name="frame">The frame.</param>
+        /// <exception cref="ArgumentException">Frame must have the same dimensions as the image - frame</exception>
+        void Add(ImageFrame<TPixel> frame);
+
+        /// <summary>
+        /// Determines whether the <seealso cref="Image{TPixel}"/> contains the <paramref name="frame"/>.
+        /// </summary>
+        /// <param name="frame">The frame.</param>
+        /// <returns>
+        ///   <c>true</c> if the <seealso cref="Image{TPixel}"/> the specified frame; otherwise, <c>false</c>.
+        /// </returns>
+        bool Contains(ImageFrame<TPixel> frame);
+
+        /// <summary>
+        /// Removes the specified frame.
+        /// </summary>
+        /// <param name="frame">The frame.</param>
+        /// <returns>true if item is found in the <seealso cref="Image{TPixel}"/>; otherwise,</returns>
+        /// <exception cref="InvalidOperationException">Cannot remove last frame</exception>
+        bool Remove(ImageFrame<TPixel> frame);
+    }
+}

src/ImageSharp/Image/ImageFrameCollection.cs

@@ -13,7 +13,7 @@ namespace SixLabors.ImageSharp
     /// Encapsulates an imaged collection of frames.
     /// </summary>
     /// <typeparam name="TPixel">The type of the pixel.</typeparam>
-    public sealed class ImageFrameCollection<TPixel> : IEnumerable<ImageFrame<TPixel>>, IDisposable
+    internal sealed class ImageFrameCollection<TPixel> : IImageFrameCollection<TPixel>, IDisposable
         where TPixel : struct, IPixel<TPixel>
     {
         private readonly IList<ImageFrame<TPixel>> frames = new List<ImageFrame<TPixel>>();

src/ImageSharp/Image/Image{TPixel}.cs

@@ -21,6 +21,7 @@ namespace SixLabors.ImageSharp
         where TPixel : struct, IPixel<TPixel>
     {
         private Configuration configuration;
+        private ImageFrameCollection<TPixel> frames;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="Image{TPixel}"/> class
@@ -61,7 +62,7 @@ namespace SixLabors.ImageSharp
         {
             this.configuration = configuration ?? Configuration.Default;
             this.MetaData = metadata ?? new ImageMetaData();
-            this.Frames = new ImageFrameCollection<TPixel>(width, height);
+            this.frames = new ImageFrameCollection<TPixel>(width, height);
         }
 
         /// <summary>
@@ -76,7 +77,7 @@ namespace SixLabors.ImageSharp
             this.configuration = configuration ?? Configuration.Default;
             this.MetaData = metadata ?? new ImageMetaData();
 
-            this.Frames = new ImageFrameCollection<TPixel>(frames);
+            this.frames = new ImageFrameCollection<TPixel>(frames);
         }
 
         /// <summary>
@@ -87,12 +88,12 @@ namespace SixLabors.ImageSharp
         /// <summary>
         /// Gets the width.
         /// </summary>
-        public int Width => this.Frames.RootFrame.Width;
+        public int Width => this.frames.RootFrame.Width;
 
         /// <summary>
         /// Gets the height.
         /// </summary>
-        public int Height => this.Frames.RootFrame.Height;
+        public int Height => this.frames.RootFrame.Height;
 
         /// <summary>
         /// Gets the meta data of the image.
@@ -102,12 +103,12 @@ namespace SixLabors.ImageSharp
         /// <summary>
         /// Gets the frames.
         /// </summary>
-        public ImageFrameCollection<TPixel> Frames { get; private set; }
+        public IImageFrameCollection<TPixel> Frames => this.frames;
 
         /// <summary>
         /// Gets the root frame.
         /// </summary>
-        private IPixelSource<TPixel> PixelSource => this.Frames?.RootFrame;
+        private IPixelSource<TPixel> PixelSource => this.frames?.RootFrame ?? throw new ObjectDisposedException(nameof(Image<TPixel>));
 
         /// <summary>
         /// Gets or sets the pixel at the specified position.
@@ -142,7 +143,7 @@ namespace SixLabors.ImageSharp
         /// <returns>Returns a new image with all the same metadata as the original.</returns>
         public Image<TPixel> Clone()
         {
-            IEnumerable<ImageFrame<TPixel>> frames = this.Frames.Select(x => x.Clone()).ToArray();
+            IEnumerable<ImageFrame<TPixel>> frames = this.frames.Select(x => x.Clone()).ToArray();
 
             return new Image<TPixel>(this.configuration, this.MetaData.Clone(), frames);
         }
@@ -161,7 +162,7 @@ namespace SixLabors.ImageSharp
         public Image<TPixel2> CloneAs<TPixel2>()
             where TPixel2 : struct, IPixel<TPixel2>
         {
-            IEnumerable<ImageFrame<TPixel2>> frames = this.Frames.Select(x => x.CloneAs<TPixel2>()).ToArray();
+            IEnumerable<ImageFrame<TPixel2>> frames = this.frames.Select(x => x.CloneAs<TPixel2>()).ToArray();
             var target = new Image<TPixel2>(this.configuration, this.MetaData, frames);
 
             return target;
@@ -172,7 +173,7 @@ namespace SixLabors.ImageSharp
         /// </summary>
         public void Dispose()
         {
-            this.Frames.Dispose();
+            this.frames.Dispose();
         }
 
         /// <summary>
@@ -183,9 +184,9 @@ namespace SixLabors.ImageSharp
         {
             Guard.NotNull(pixelSource, nameof(pixelSource));
 
-            for (int i = 0; i < this.Frames.Count; i++)
+            for (int i = 0; i < this.frames.Count; i++)
             {
-                this.Frames[i].SwapPixelsBuffers(pixelSource.Frames[i]);
+                this.frames[i].SwapPixelsBuffers(pixelSource.frames[i]);
             }
         }
     }