Added method to IImageBase that can be used to initialize the pixels of an image.

src/ImageSharp/Image/IImageBase.cs

@@ -19,6 +19,16 @@ namespace ImageSharp
         /// </summary>
         TColor[] Pixels { get; }
 
+        /// <summary>
+        /// Sets the size of the pixel array of the image to the given width and height.
+        /// </summary>
+        /// <param name="width">The new width of the image. Must be greater than zero.</param>
+        /// <param name="height">The new height of the image. Must be greater than zero.</param>
+        /// <exception cref="System.ArgumentOutOfRangeException">
+        /// Thrown if either <paramref name="width"/> or <paramref name="height"/> are less than or equal to 0.
+        /// </exception>
+        void InitPixels(int width, int height);
+
         /// <summary>
         /// Sets the pixel array of the image to the given value.
         /// </summary>

src/ImageSharp/Image/ImageBase.cs

@@ -41,12 +41,7 @@ namespace ImageSharp
         /// </exception>
         protected ImageBase(int width, int height)
         {
-            Guard.MustBeGreaterThan(width, 0, nameof(width));
-            Guard.MustBeGreaterThan(height, 0, nameof(height));
-
-            this.Width = width;
-            this.Height = height;
-            this.pixelBuffer = new TColor[width * height];
+            this.InitPixels(width, height);
         }
 
         /// <summary>
@@ -102,6 +97,17 @@ namespace ImageSharp
         /// <inheritdoc/>
         public int FrameDelay { get; set; }
 
+        /// <inheritdoc/>
+        public void InitPixels(int width, int height)
+        {
+            Guard.MustBeGreaterThan(width, 0, nameof(width));
+            Guard.MustBeGreaterThan(height, 0, nameof(height));
+
+            this.Width = width;
+            this.Height = height;
+            this.pixelBuffer = new TColor[width * height];
+        }
+
         /// <inheritdoc/>
         public void SetPixels(int width, int height, TColor[] pixels)
         {