Justin Rogers

ImageFast: A stand-alone library for quickly loading GDI+ images without validation.

/*
    Copyright (c) 2004 DigiTec Web Consultants, LLC.  All rights reserved.

    The use of this software is for test and performance purposes only.
    You may not use this software in any commercial applications without
    the express permission of the copyright holder.  You may add to or
    modify the code contained here-in to cause it to run slower without
    contacting the copyright holder, however, any attempts to make this
    code run faster should be documented on:
    
    http://weblogs.asp.net/justin_rogers/articles/131704.aspx
    
    I reserve the right to change or modify the publicly available version
    of this code at any time.  I will not provide version protection, so
    if you have reliance on a particular build of this software, then make
    your own back-ups.
   
    You must laugh, at least a little, when reading this licensing agreement,
    unless of course you don't have a sense of humor.  In all seriousness,
    excluding the laughter, laughter in itself does not void this license
    agreement, nor compromise it's ability to legally bind you.
   
    You must not remove this notice, or any other, from this software.
*/

/*
    Need some notes on use.  I previously published a blog entry describing
    this guy, but the end result was that unless you had already done some
    GDI+ work, my library would fail.  The reason it works in Windows Forms
    applications is because WinForms uses and initializes the library
    correctly before I get there.  However, try to load ImageFast stand-alone
    and all you get is a NullReferenceException.
   
    I'm past all of that now.  We correctly call GdiplusStartup and
    GdiplusShutdown (hopefully).  In addition, I've added more thorough image
    loading support by providing metafile loaders.
   
    To compile a release library:
        csc /t:library /optimize+ ImageFast.cs
       
    To compile a debug library with some console output:
        csc /t:library /debug+ /d:DEBUG,TRACE ImageFast.cs
       
    NOTE: This is now ready for ASP .NET users.  I've verified all of the
    different startup paths and shutdown paths to make sure there isn't
    anything strange with the libraries that would prevent them from
    running under ASP .NET without special tuning or instrumentation.
*/

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;

public class ImageFast {
    [DllImport("gdiplus.dll", ExactSpelling=true, CharSet=CharSet.Unicode)]
    private static extern int GdipLoadImageFromFile(string filename, out IntPtr image);
   
    [DllImport("gdiplus.dll", ExactSpelling=true, CharSet=CharSet.Unicode)]
    private static extern int GdiplusStartup(out IntPtr token, ref StartupInput input, out StartupOutput output);
   
    [DllImport("gdiplus.dll", ExactSpelling=true, CharSet=CharSet.Unicode)]
    private static extern int GdiplusShutdown(IntPtr token);

    [DllImport("gdiplus.dll", ExactSpelling=true, CharSet=CharSet.Unicode)]
    private static extern int GdipGetImageType(IntPtr image, out GdipImageTypeEnum type);
   
    private static IntPtr gdipToken = IntPtr.Zero;
   
    static ImageFast() {
#if DEBUG
        Console.WriteLine("Initializing GDI+");
#endif
        if ( gdipToken == IntPtr.Zero ) {
            StartupInput input = StartupInput.GetDefaultStartupInput();
            StartupOutput output;

            int status = GdiplusStartup(out gdipToken, ref input, out output);
#if DEBUG
            if ( status == 0 )
                Console.WriteLine("Initializing GDI+ completed successfully");
#endif
            if ( status == 0 )
                AppDomain.CurrentDomain.ProcessExit += new EventHandler(Cleanup_Gdiplus);
        }
    }
   
    private static void Cleanup_Gdiplus(object sender, EventArgs e) {
#if DEBUG
        Console.WriteLine("GDI+ shutdown entered through ProcessExit event");
#endif
        if ( gdipToken != IntPtr.Zero )
            GdiplusShutdown(gdipToken);

#if DEBUG
        Console.WriteLine("GDI+ shutdown completed");
#endif
    }
   
    private static Type bmpType = typeof(System.Drawing.Bitmap);
    private static Type emfType = typeof(System.Drawing.Imaging.Metafile);

    public static Image FromFile(string filename) {
        filename = Path.GetFullPath(filename);
        IntPtr loadingImage = IntPtr.Zero;
       
        // We are not using ICM at all, fudge that, this should be FAAAAAST!
        if ( GdipLoadImageFromFile(filename, out loadingImage) != 0 ) {
            throw new Exception("GDI+ threw a status error code.");
        }
       
        GdipImageTypeEnum imageType;
        if ( GdipGetImageType(loadingImage, out imageType) != 0 ) {
            throw new Exception("GDI+ couldn't get the image type");
        }
       
        switch(imageType) {
            case GdipImageTypeEnum.Bitmap:
                return (Bitmap) bmpType.InvokeMember("FromGDIplus", BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.InvokeMethod, null, null, new object[] { loadingImage });
            case GdipImageTypeEnum.Metafile:
                return (Metafile) emfType.InvokeMember("FromGDIplus", BindingFlags.NonPublic | BindingFlags.Static | BindingFlags.InvokeMethod, null, null, new object[] { loadingImage });
        }
       
        throw new Exception("Couldn't convert underlying GDI+ object to managed object");
    }

    private ImageFast() { }
}

[StructLayout(LayoutKind.Sequential)]
internal struct StartupInput {
    public int GdiplusVersion;
    public IntPtr DebugEventCallback;
    public bool SuppressBackgroundThread;
    public bool SuppressExternalCodecs;
   
    public static StartupInput GetDefaultStartupInput() {
        StartupInput result = new StartupInput();
        result.GdiplusVersion = 1;
        result.SuppressBackgroundThread = false;
        result.SuppressExternalCodecs  = false;
        return result;
    }
}

[StructLayout(LayoutKind.Sequential)]
internal struct StartupOutput
{
    public IntPtr Hook;
    public IntPtr Unhook;
}

internal enum GdipImageTypeEnum {
    Unknown = 0,
    Bitmap = 1,
    Metafile = 2
}