Added IThumbnailProvider

PInvoke/Shell32/Thumbcache.cs

@@ -0,0 +1,41 @@
+using System;
+using System.Runtime.InteropServices;
+
+// ReSharper disable InconsistentNaming
+
+namespace Vanara.PInvoke
+{
+    public static partial class Shell32
+	{
+        /// <summary>Alpha channel type information.</summary>
+        public enum WTS_ALPHATYPE
+        {
+            /// <summary>The bitmap is an unknown format. The Shell tries nonetheless to detect whether the image has an alpha channel.</summary>
+            WTSAT_UNKNOWN = 0x0,
+            /// <summary>The bitmap is an RGB image without alpha. The alpha channel is invalid and the Shell ignores it.</summary>
+            WTSAT_RGB = 0x1,
+            /// <summary>The bitmap is an ARGB image with a valid alpha channel.</summary>
+            WTSAT_ARGB = 0x2
+        }
+
+        /// <summary>Exposes a method for getting a thumbnail image.</summary>
+        [ComImport, Guid("e357fccd-a995-4576-b01f-234630154e96"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
+        public interface IThumbnailProvider
+        {
+            /// <summary>Gets a thumbnail image and alpha type.</summary>
+            /// <param name="cx">
+            /// The maximum thumbnail size, in pixels. The Shell draws the returned bitmap at this size or smaller. The returned bitmap should fit into a square
+            /// of width and height cx, though it does not need to be a square image. The Shell scales the bitmap to render at lower sizes. For example, if the
+            /// image has a 6:4 aspect ratio, then the returned bitmap should also have a 6:4 aspect ratio.
+            /// </param>
+            /// <param name="phbmp">
+            /// When this method returns, contains a pointer to the thumbnail image handle. The image must be a DIB section and 32 bits per pixel. The Shell
+            /// scales down the bitmap if its width or height is larger than the size specified by cx. The Shell always respects the aspect ratio and never
+            /// scales a bitmap larger than its original size.
+            /// </param>
+            /// <param name="pdwAlpha">When this method returns, contains a pointer to one of the following values from the WTS_ALPHATYPE enumeration.</param>
+            /// <returns>If this method succeeds, it returns S_OK. Otherwise, it returns an HRESULT error code.</returns>
+            void GetThumbnail(uint cx, out IntPtr phbmp, out WTS_ALPHATYPE pdwAlpha);
+        }
+    }
+}