How to have large file icons with SHGetFileInfo in C#

HELLO WORLD,

for a long while people have been complaining about our icons being unsharp and “pixelated”… indeed they were, and the reason was we were using SHGetFileInfo (a Windows Shell API function) to obtain the file icon from the file path. This function can only cannot return the high definition icons we see in Windows Vista and Windows, such as the following:

Tabbles with large icons

So we started to investigate how to obtain the hi-res icons (called “jumbo” and “extralarge”) and found this article on how to get large icons using C++. The problem was to convert this code to C#. This is not easy, at least for me, because it requires, among other things, to write a wrapper for a COM interface, and I had no experience with this. Finally, with the help of this article, I made it. You can find the code below. (Remember that the interesting function is icon_of_path_large, whereas icon_of_path is the old function which can only return a low-res icon.)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Media.Imaging;
using System.Windows.Media;
using System.Diagnostics;

namespace WpfControlLibrary1
{
    public class c_icon_of_path
    {
        // Constants that we need in the function call

        private const int SHGFI_ICON = 0x100;

        private const int SHGFI_SMALLICON = 0x1;

        private const int SHGFI_LARGEICON = 0x0;

        private const int SHIL_JUMBO = 0x4;
        private const int SHIL_EXTRALARGE = 0x2;

        // This structure will contain information about the file

        public struct SHFILEINFO
        {

            // Handle to the icon representing the file

            public IntPtr hIcon;

            // Index of the icon within the image list

            public int iIcon;

            // Various attributes of the file

            public uint dwAttributes;

            // Path to the file

            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 256)]

            public string szDisplayName;

            // File type

            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]

            public string szTypeName;

        };

        [System.Runtime.InteropServices.DllImport("Kernel32.dll")]
        public static extern Boolean CloseHandle(IntPtr handle);

        private struct IMAGELISTDRAWPARAMS
        {
            public int cbSize;
            public IntPtr himl;
            public int i;
            public IntPtr hdcDst;
            public int x;
            public int y;
            public int cx;
            public int cy;
            public int xBitmap;        // x offest from the upperleft of bitmap
            public int yBitmap;        // y offset from the upperleft of bitmap
            public int rgbBk;
            public int rgbFg;
            public int fStyle;
            public int dwRop;
            public int fState;
            public int Frame;
            public int crEffect;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct IMAGEINFO
        {
            public IntPtr hbmImage;
            public IntPtr hbmMask;
            public int Unused1;
            public int Unused2;
            public RECT rcImage;
        }

        #region Private ImageList COM Interop (XP)
        [ComImportAttribute()]
        [GuidAttribute("46EB5926-582E-4017-9FDF-E8998DAA0950")]
        [InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)]
        //helpstring("Image List"),
        interface IImageList
        {
            [PreserveSig]
            int Add(
                IntPtr hbmImage,
                IntPtr hbmMask,
                ref int pi);

            [PreserveSig]
            int ReplaceIcon(
                int i,
                IntPtr hicon,
                ref int pi);

            [PreserveSig]
            int SetOverlayImage(
                int iImage,
                int iOverlay);

            [PreserveSig]
            int Replace(
                int i,
                IntPtr hbmImage,
                IntPtr hbmMask);

            [PreserveSig]
            int AddMasked(
                IntPtr hbmImage,
                int crMask,
                ref int pi);

            [PreserveSig]
            int Draw(
                ref IMAGELISTDRAWPARAMS pimldp);

            [PreserveSig]
            int Remove(
            int i);

            [PreserveSig]
            int GetIcon(
                int i,
                int flags,
                ref IntPtr picon);

            [PreserveSig]
            int GetImageInfo(
                int i,
                ref IMAGEINFO pImageInfo);

            [PreserveSig]
            int Copy(
                int iDst,
                IImageList punkSrc,
                int iSrc,
                int uFlags);

            [PreserveSig]
            int Merge(
                int i1,
                IImageList punk2,
                int i2,
                int dx,
                int dy,
                ref Guid riid,
                ref IntPtr ppv);

            [PreserveSig]
            int Clone(
                ref Guid riid,
                ref IntPtr ppv);

            [PreserveSig]
            int GetImageRect(
                int i,
                ref RECT prc);

            [PreserveSig]
            int GetIconSize(
                ref int cx,
                ref int cy);

            [PreserveSig]
            int SetIconSize(
                int cx,
                int cy);

            [PreserveSig]
            int GetImageCount(
            ref int pi);

            [PreserveSig]
            int SetImageCount(
                int uNewCount);

            [PreserveSig]
            int SetBkColor(
                int clrBk,
                ref int pclr);

            [PreserveSig]
            int GetBkColor(
                ref int pclr);

            [PreserveSig]
            int BeginDrag(
                int iTrack,
                int dxHotspot,
                int dyHotspot);

            [PreserveSig]
            int EndDrag();

            [PreserveSig]
            int DragEnter(
                IntPtr hwndLock,
                int x,
                int y);

            [PreserveSig]
            int DragLeave(
                IntPtr hwndLock);

            [PreserveSig]
            int DragMove(
                int x,
                int y);

            [PreserveSig]
            int SetDragCursorImage(
                ref IImageList punk,
                int iDrag,
                int dxHotspot,
                int dyHotspot);

            [PreserveSig]
            int DragShowNolock(
                int fShow);

            [PreserveSig]
            int GetDragImage(
                ref POINT ppt,
                ref POINT pptHotspot,
                ref Guid riid,
                ref IntPtr ppv);

            [PreserveSig]
            int GetItemFlags(
                int i,
                ref int dwFlags);

            [PreserveSig]
            int GetOverlayImage(
                int iOverlay,
                ref int piIndex);
        };
        #endregion

        ///
        /// SHGetImageList is not exported correctly in XP.  See KB316931
        /// http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q316931
        /// Apparently (and hopefully) ordinal 727 isn't going to change.
        ///
        [DllImport("shell32.dll", EntryPoint = "#727")]
        private extern static int SHGetImageList(
            int iImageList,
            ref Guid riid,
            out IImageList ppv
            );

        // The signature of SHGetFileInfo (located in Shell32.dll)
        [DllImport("Shell32.dll")]
        public static extern int SHGetFileInfo(string pszPath, int dwFileAttributes, ref SHFILEINFO psfi, int cbFileInfo, uint uFlags);

        [DllImport("Shell32.dll")]
        public static extern int SHGetFileInfo(IntPtr pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, int cbFileInfo, uint uFlags);

        [DllImport("shell32.dll", SetLastError = true)]
        static extern int SHGetSpecialFolderLocation(IntPtr hwndOwner, Int32 nFolder,
                 ref IntPtr ppidl);

        [DllImport("user32")]
        public static extern int DestroyIcon(IntPtr hIcon);

        public struct pair
        {
            public System.Drawing.Icon icon {get;set;}
            public IntPtr iconHandleToDestroy{set;get;}

        }

        public static int DestroyIcon2(IntPtr hIcon)
        {
            return DestroyIcon(hIcon);
        }

        private static BitmapSource bitmap_source_of_icon  ( System.Drawing.Icon ic) {
                var ic2 = System.Windows.Interop.Imaging.CreateBitmapSourceFromHIcon(ic.Handle,
                                                        System.Windows.Int32Rect.Empty,
                                                        System.Windows.Media.Imaging.BitmapSizeOptions.FromEmptyOptions( ) );
                ic2.Freeze();
                return ((BitmapSource) ic2 );
        }

        public static BitmapSource SystemIcon(bool small, ShellLib.ShellApi.CSIDL csidl)
        {

            IntPtr pidlTrash = IntPtr.Zero;
            int hr = SHGetSpecialFolderLocation(IntPtr.Zero, (int) csidl, ref pidlTrash);
            Debug.Assert(hr == 0);

            SHFILEINFO shinfo = new SHFILEINFO();

            uint SHGFI_USEFILEATTRIBUTES = 0x000000010;

            // Get a handle to the large icon
            uint flags;
            uint SHGFI_PIDL = 0x000000008;
            if (!small)
            {
                flags = SHGFI_PIDL | SHGFI_ICON | SHGFI_LARGEICON | SHGFI_USEFILEATTRIBUTES;
            }
            else{
                flags = SHGFI_PIDL | SHGFI_ICON | SHGFI_SMALLICON | SHGFI_USEFILEATTRIBUTES;
            }

            var res = SHGetFileInfo(pidlTrash, 0, ref shinfo, Marshal.SizeOf(shinfo), flags);
            Debug.Assert(res != 0);

            var myIcon = System.Drawing.Icon.FromHandle(shinfo.hIcon);
            Marshal.FreeCoTaskMem(pidlTrash);
            var bs = bitmap_source_of_icon(myIcon);
            myIcon.Dispose();
            bs.Freeze(); // importantissimo se no fa memory leak
            DestroyIcon(shinfo.hIcon);
            CloseHandle(shinfo.hIcon);
            return bs;

        }

        public static BitmapSource icon_of_path(string FileName, bool small, bool checkDisk, bool addOverlay)
        {
            SHFILEINFO shinfo = new SHFILEINFO();

            uint SHGFI_USEFILEATTRIBUTES = 0x000000010;
            uint SHGFI_LINKOVERLAY = 0x000008000;

            uint flags;
            if (small)
            {
                flags = SHGFI_ICON | SHGFI_SMALLICON ;
            }
            else{
                flags = SHGFI_ICON | SHGFI_LARGEICON ;
            }
            if (!checkDisk)
                flags |= SHGFI_USEFILEATTRIBUTES;
            if (addOverlay)
                flags |= SHGFI_LINKOVERLAY;

            var res = SHGetFileInfo(FileName, 0, ref shinfo, Marshal.SizeOf(shinfo), flags);
            if (res == 0)
            {
                throw(new System.IO.FileNotFoundException());
            }

            var myIcon = System.Drawing.Icon.FromHandle(shinfo.hIcon);

            var bs = bitmap_source_of_icon(myIcon);
            myIcon.Dispose();
            bs.Freeze(); // importantissimo se no fa memory leak
            DestroyIcon(shinfo.hIcon);
            CloseHandle(shinfo.hIcon);
            return bs;

        }

        public static BitmapSource icon_of_path_large(string FileName, bool jumbo, bool checkDisk)
        {

            SHFILEINFO shinfo = new SHFILEINFO();

            uint SHGFI_USEFILEATTRIBUTES = 0x000000010;
            uint SHGFI_SYSICONINDEX = 0x4000;

            int FILE_ATTRIBUTE_NORMAL = 0x80;

            uint flags;
            flags = SHGFI_SYSICONINDEX;

            if (!checkDisk)  // This does not seem to work. If I try it, a folder icon is always returned.
                flags |= SHGFI_USEFILEATTRIBUTES ;

            var res = SHGetFileInfo(FileName, FILE_ATTRIBUTE_NORMAL, ref shinfo, Marshal.SizeOf(shinfo), flags);
            if (res == 0)
            {
                throw (new System.IO.FileNotFoundException());
            }
            var iconIndex = shinfo.iIcon;

            // Get the System IImageList object from the Shell:
            Guid iidImageList = new Guid("46EB5926-582E-4017-9FDF-E8998DAA0950");

            IImageList iml;
            int size = jumbo ? SHIL_JUMBO : SHIL_EXTRALARGE;
            var hres = SHGetImageList(size, ref iidImageList, out  iml); // writes iml
            //if (hres == 0)
            //{
            //    throw (new System.Exception("Error SHGetImageList"));
            //}

            IntPtr hIcon = IntPtr.Zero;
            int ILD_TRANSPARENT = 1;
            hres = iml.GetIcon(iconIndex, ILD_TRANSPARENT, ref hIcon);
            //if (hres == 0)
            //{
            //    throw (new System.Exception("Error iml.GetIcon"));
            //}

            var myIcon = System.Drawing.Icon.FromHandle(hIcon);
            var bs = bitmap_source_of_icon(myIcon);
            myIcon.Dispose();
            bs.Freeze(); // very important to avoid memory leak
            DestroyIcon(hIcon);
            CloseHandle(hIcon);

            return bs;

        }
    }
}

You can download Tabbles on our download page!

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