Introduction
If you own applications such as Blogs, Forums or Wiki and strive to delight your customers with every new release, you probably don't need justification for this feature. In this article, I'll show you how you can allow your users to type in math equations and have them rendered in nice textbook format with absolutely minimal coding effort on your part.
The basic idea is to let the user type in something like this: <img src=".?$ x^2 = 25 $">
The above request first goes to your default.aspx file, where a line of code detects if it's a request for an image and transfers it to a handler. The handler uses MimeTeX to generate the GIF file for the equation and returns to the browser. Fortunately, you don't have to care about any of these, as it's all wrapped and ready for drag and drop.
If you are responsible for any of these types of applications, you owe it to your users to give them this ability:
- Blogs
- Forums
- Wiki
- Email apps
- Instant messengers
- HTML editors
- Word processing
Essentially, any application that ultimately renders user content in graphical form can add this feature. It doesn't have to be HTML content. For instance, a note-keeping software can detect the TeX content during editing surrounded by $ markers and replace them with a nice graphical form. It can use the exact same library given in this article for this purpose.
Tip:
How to show equations without any coding or even having your own server?
If you don't want to deploy and maintain code in this article, you can use my server for free. You can also use it on ANY blogs, Wikis or websites which do not support TeX and math equations.
To use my server, append http: by the equation you want. Here's an example:
<img src="http://www.shitalshah.com?$ x^2 = 25 $">
Give it a try! |
Background
MimeTeX is the guts of this code. MimeTeX is written by John Forkosh to mainly run under UNIX and as a CGI EXE under Windows. Obviously, while this works, it has many disadvantages like you have to have an ability to run a CGI EXE on IIS, which is a difficult feature for shared IIS hosting. Even if you have a dedicated server, the CGI EXE solution won't scale if you want to support thousands of users. Also, users would be required to add mimetex.exe into the image tag's source, which is less intuitive for users of applications like Blogs or Forums.
For this reason, I decided to convert the MimeTeX code into a Win32 DLL. This is a pretty simple task of taking C files, creating a VC++ Win32 DLL project, adding a DLL export and making other minor changes. But the bigger problem comes later: the DLL runs in-process and hence we should make sure that the C code is free from memory leaks. Unfortunately, this wasn't the case, but fortunately the debug functions like _CrtDumpMemoryLeaks and the VC++ IDE made it a little easier to find them. So, after a weekend's effort, this uncharted UNIX code was free from all known memory leaks. Over the next couple of weeks, John Forkosh and I were exchanging long emails discussing the 10 lines of changes I had made, analyzing them, perfecting them and thoroughly testing the code. It was great fun. The result was the MimeTeX Win32 DLL, which you can now call from your .NET code using DLLImport.
My next step was to create the ASP.NET IHttpHandler that would wrap this call, add caching on top of it and allow other customizations and admin functionality.
Using the Code
You can use this code in three ways:
- Integrate with your own web apps
Download the code, add the files in the folder named OnlyRequiredFiles (For VB.NET, look under the VB.NET Version folder) into your ASP.NET project and drop the MimeTex.DLL in the bin folder. Edit your default.aspx page and put this line somewhere in Page_Load or Page_Init (if you are using custom page templates):
Astrila.Eq2Img.ShowEq.HandleEquationQueries();
Recompile! Make sure the CachedEqImages folder exists and the ASP.NET user has write permissions for it. That's all there is! You may now create an HTML file in the virtual root folder with an example image tag the same as the one shown at the start of this article for testing.
- Use as a separate web app
Copy the Eq2Img folder in your wwwroot. Create a virtual folder, make sure the CachedEqImages folder exists and the ASP.NET user has write permissions for it, and that default.aspx is configured as the default page. You should now be up and running! Remember, your users would need to reference this virtual folder in the image tags like this: <img src="Eq2Img?$ x^2 = 25 $">
- Use in desktop apps
This is pretty easy. You just need to DLLImport MimeTex.DLL and call the CreateGifForEq function from your Windows Forms app like this:
[System.Runtime.InteropServices.DllImport("MimeTex.dll")]
internal static extern int CreateGifFromEq(string expr,
string fileName);
You can look into a sample Windows Forms app in the Eq2ImgWinForms folder, which looks like this:
The next question might be what is the format of the equations? How do you write Greek symbols, integrals, limits and so on? The format is known as TeX (or LaTeX) and you might be familiar with it if you have ever authored a scientific document in your school years. If not, it's a pretty simple format to learn. For instance, to display the pi symbol you just write \pi and to display the integration sign you write \int and so on. You can find good documentation here and here, but if you choose to be lazy, just use the free WYSWYG equation editor called TeXAide which will build the TeX string for you. Note that TeX ignores white spaces.
Points of Interest
You might have noticed that MimeTeX goes beyond just supporting the equations conforming to TeX format. For instance, you can also create sophisticated figures using LaTeX commands such as the following:
This is really cool because this feature allows your users to author scientific content just with MimeTeX. More examples are at John's website.
I've also thrown in some admin functionality to let you delete cache files (these are very small, typically 1 KB JPG files). You can access this using Eq2ImgAdmin.aspx. This page also lets you dynamically unload the MimeTeX DLL. Remember that this is a pure Win32 DLL, so it gets locked by the ASP.NET process once it gets loaded, unlike managed .NET DLLs. That means you can't update the DLL without restarting the IIS, an unfortunate scenario for shared hosting or even otherwise. To solve this problem, the admin page allows you to dynamically unload this unmanaged DLL from the process on demand. For the technically curious, I simply used GetModuleHandle and FreeLibrary Windows API calls. The admin functionality by default is not enabled. Follow the messages it shows to enable it. Also note that you can exclude this page completely without losing the core functionality.
The code supports a bunch of customization settings that you can put in web.config. By default none are required, but if you prefer, for example, you can choose to run MimeTeX out of the process instead of in-proc or you can run it as CGI or from an external URL. You can set the maximum length of equation strings and maximum cache size and cache folder and so on. I haven't got enough time to document them, but they are easy to figure out from the class Eq2ImgSettings and they all take the form:
<appSettings>
<add key="Eq2Img_ClientCacheAgeInSeconds" value="200" />
</appSettings>
Finally, here's the security disclosure you all have been waiting for: you are running unmanaged code from ASP.NET when you call into the MimeTeX DLL. That means ASP.NET should have sufficient permission for this (by default it does). However, the bigger concern is the possible nasty C bugs such as memory leaks and invalid pointers that might make your website unstable. In my testing, it does work satisfactorily; the in-proc mode is very scalable and MimeTeX itself has been in use on many websites since 2002. However, if you ever notice a problem, you do have an exit strategy of setting an option in your web.config file so that MimeTeX will run out of process or even completely disable it and serve only the cached files. As MimeTeX is an open source project, anyone has the liberty to fix the bugs as soon as they are found.
Need Help?
I'm passionate about enabling the web to allow users to author scientific content. If you have any problems using this code in your application, you can contact me for free assistance.
History
- 23rd August, 2005 - Newly created.
- 24th August, 2005 - Fixed a concurrency bug, created VB.NET version of the code.
- 30th January, 2008 - Article content updated
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 | Hi 
Member 2646037 | 0:46 18 Sep '09 |
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Plz Help. Thanks In Advance
I have some concerns about MimeTex.
1. It is compulsary to have default.aspx in the application, coz my login page is treated as default page.
2. Mine is a web application which has many folder and sub folders
is it compulsary to have the files in the "OnlyRequiredFiles" on the root of the application.
3.I have pasted the line "Astrila.Eq2Img.ShowEq.HandleEquationQueries()" in the page load event of the login page.But i have to show the equation in some other page inside.so that does not work..
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Hi !
Thanks for providing great solution to for Equations in .NET. 
I liked it very much. But initially it didnt worked. I wondered what makes it throwing error like, "Unable to load MimeTex.DLL", 
Then when I put MimeTex.DLL in C:\Windows\System32, it worked like a charm.
Any solution to keep MimeTex.DLL to Bin directory of the app only?
Thanks once again for such a great help. 
Girish Advani
India
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Thanks for providing this. I like the way it works. It was easy to incorporate into a vs 2008 project. It could rightly be called elegant.
Web development isn't my usual area, but I can't wait to spring this on my fellow developers at our next project meeting. Requirements met and then some. Good chance that it will make it into production. I can't see anyone beating this. Sweet.
Thanks again.
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I'd just like to say that a phenomenal job was done to get this working. I'm a little mad/sad b/c I wanted to develop something like this on my own, but you've beat me to the punch... and using the C++ wrapper is ingenious! I'd love to hear, in more detail, how the wrapping was handled and then debugged. Again, great work!
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MimeTeX is really a very useful library to have if you want to display professional-looking equations in an application.
My only problem is that I would really like to use it within a 64-bit application (developed in Visual Studio 2008).
I'm using the Windows 7 Release Candidate, and at the moment, I can only load the DLL if I set my project's Platform Target (under Properties->Build) to "x86" instead of "Any CPU".
I believe this means that it will then run as a 32-bit application, with all the corresponding memory limitations.
I can't confirm this, but I assume that 64-bit Vista users have the same problem.
Are there any plans to release a 64-bit version of the DLL?
(or is it trivial for me to build one directly from the source?)
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I followed the instructions and am getting an error:
System.DllNotFoundException was unhandled by user code
Message="Unable to load DLL 'MimeTex.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)"
Source="App_Code.gq87t5ot"
TypeName=""
I have made sure the DLL MimeTex.dll is in the bin folder.
The error is App_Code/ShowEq.cs Line 126 in the following method:
private void CreateGifUsingInProc(HttpContext context, string equation, string filePathForCachedEqImage, Eq2ImgSettings settings)
{
lock(_MimeTeXCallLocker)
{
NativeMethods.CreateGifFromEq(equation, filePathForCachedEqImage);
}
}
I am using VS 2008 and running the application in the Eq2img folder.
Any help would be appreciated.
Thanks
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 | Simple
alhimikyr | 2:47 28 Dec '08 |
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I'm try to use "OnlyRequiredFiles" way in two different web projects, but both times I get the same problem: "Error 46 Could not load type 'Astrila.Eq2Img.Eq2ImgAdmin'. D:\Projects\Test\Eq2ImgAdmin.aspx Line 1". But I didn't make any changes of "Eq2ImgAdmin.aspx" or "Eq2ImgAdmin.aspx.cs" file. I just copied all files from "OnlyRequiredFiles" folder to my web-project root folder and added using Astrila.Eq2Img; and Astrila.Eq2Img.ShowEq.HandleEquationQueries(); to "Page_Load" method. Also I just copied "MimeTeX.dll" to bin folder. Am I doing something wrong? How can I fix it? Thanks.
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Dear Sir or Madam
I'm a novice programmer (first year college
freshman) and I'm trying to study your code
but I'm incapable to get the whole picture.
Please can you point out a resource
where I can study the algorithm
before approaching its code
implementation ?
Thanks in advance.
Warmest regards.
Fernando Fermi
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| General
Jorge Bay Gondra | 4:31 22 Aug '08 |
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Great work! Out of curiosity, is your mimetex.dll compiled with the anti-aliasing option? The resulting text looks like it could be quite a bit smoother. And if I try doing white text on a black background, the result is really bad looking. These are small gripes for an otherwise excellent effort.
I've been looking for a way to write a Compact Framework application that uses LaTeX, and this allows me to do that. I would have preferred having that functionality built into the app, but sending a webrequest to a website to fetch the image works well enough.
Any chance of you releasing the source code for the mimetex.dll?
Thanks again!!
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When I try to compile the MimeTeX solution I get the following error:
"MimeTeX error LNK2001: unresolved external symbol _gifSize"
Sounds like I'm missing a file if the linker can't resolve a symbol.
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| PNG
nbastos | 0:07 23 Oct '07 |
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The DLL declaration MimTeX.dll in Visual Basic 6, parameter passing is causing problems.
I get "run-time error 49: Bad DLL calling convention"
Declare Function CreateGifFromEq Lib "MimeTex.dll" (ByVal expr As String, ByVal FileName As String)
Thanks,
-- Igor
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Dear Igorpett,
Since MimTeX.dll uses C-calling convention, we cannot call its function directly.
Try the following code.
I hope you can solve the matter.
Best regards,
Nguyen Quoc San
quocsan@gmail.com
(From Vietnam)
' (I got this module somewhere in the Internet and I forget the author. Sorry!)
' ~~~ Start of Code
Option Explicit
Public Enum DECLSPEC
eStdCall = 0
eCDecl
End Enum
Private Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
Private Declare Function GetProcAddress Lib "kernel32" _
(ByVal hModule As Long, ByVal lpProcName As String) As Long
Private Declare Function CallWindowProc Lib "User32" Alias "CallWindowProcA" ( _
ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long
Private Declare Function FreeLibrary Lib "kernel32" (ByVal hLibModule As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
(lpDest As Any, lpSource As Any, ByVal cBytes As Long)
Private m_opIndex As Long
Private m_OpCode() As Byte Public Function RunDll32(ByVal LibFileName As String, ByVal ProcName As String, _
ByVal CallingType As DECLSPEC, ParamArray Params()) As Long
Dim hProc As Long, hModule As Long
ReDim m_OpCode(400 + 6 * UBound(Params)) hModule = LoadLibrary(ByVal LibFileName) If hModule = 0 Then
MsgBox "Unable to load library'" & LibFileName & "'"
Exit Function
End If
hProc = GetProcAddress(hModule, ByVal ProcName)
If hProc = 0 Then: FreeLibrary hModule: Exit Function:
RunDll32 = CallWindowProc(GetCodeStart(hProc, CallingType, Params), 0, 1, 2, 3) FreeLibrary hModule
End Function
Private Function GetCodeStart _
(ByVal lngProc As Long, ByVal CallingType As DECLSPEC, ByVal arrParams As Variant) As Long
Dim i As Long, lCodeStart As Long
lCodeStart = (VarPtr(m_OpCode(0)) Or &HF) + 1
m_opIndex = lCodeStart - VarPtr(m_OpCode(0))
For i = 0 To m_opIndex - 1
m_OpCode(i) = &HCC Next i
PrepareStack
For i = UBound(arrParams) To 0 Step -1
AddByteToCode &H68 AddLongToCode CLng(arrParams(i))
Next i
AddByteToCode &HE8 AddLongToCode lngProc - VarPtr(m_OpCode(m_opIndex)) - 4
If CallingType = eCDecl Then Call ClearStack(arrParams)
AddByteToCode &HC3 AddByteToCode &HCC
GetCodeStart = lCodeStart
End Function
Private Sub ClearStack(ByVal Params As Variant)
Dim i As Long
For i = 0 To UBound(Params)
AddByteToCode &H59 Next
End Sub
Private Sub PrepareStack()
AddByteToCode &H58 AddByteToCode &H59 AddByteToCode &H59 AddByteToCode &H59 AddByteToCode &H59 AddByteToCode &H50 End Sub
Private Sub AddLongToCode(lData As Long) CopyMemory m_OpCode(m_opIndex), lData, 4
m_opIndex = m_opIndex + 4
End Sub
Private Sub AddByteToCode(bData As Byte) m_OpCode(m_opIndex) = bData
m_opIndex = m_opIndex + 1
End Sub
Option Explicit
Private Declare Function GetTempFileName Lib "kernel32" Alias "GetTempFileNameA" (ByVal lpszPath As String, ByVal lpPrefixString As String, ByVal wUnique As Long, ByVal lpTempFileName As String) As Long
Private Declare Function GetTempPath Lib "kernel32" Alias "GetTempPathA" (ByVal nBufferLength As Long, ByVal lpBuffer As String) As Long
Private Const MAX_PATH = 260
Function GetTempFile() As String
Dim temp_path As String
Dim temp_file As String
Dim Length As Long
temp_path = Space(MAX_PATH)
Length = GetTempPath(MAX_PATH, temp_path)
temp_path = Left(temp_path, Length)
temp_file = Space(MAX_PATH)
GetTempFileName temp_path, "tmp", 0, temp_file
GetTempFile = Left(temp_file, InStr(temp_file, vbNullChar) - 1)
End Function
Function Eq2Img(ByVal sEQ As String, ByVal sPath As String) As Boolean
Call RunDll32("MimeTeX.dll", "CreateGifFromEq", eCDecl, StrPtr(StrConv(sEQ, vbFromUnicode)), StrPtr(StrConv(sPath, vbFromUnicode)))
Eq2Img = Len(Dir(sPath)) > 0
End Function
Sub Eq2GIF()
If Windows.count < 1 Then Exit Sub
Dim sPath As String, sEQ As String
sEQ = Trim(Selection.Text)
Selection.Text = " "
sPath = GetTempFile
If Len(sPath) = 0 Then Exit Sub
If Not Eq2Img(sEQ, sPath) Then Exit Sub
sPath, LinkToFile:=False, SaveWithDocument:=True).WrapFormat.Type = _
wdWrapTopBottom
Dim iSh As InlineShape
Set iSh = ActiveDocument.InlineShapes.AddPicture(Filename:=sPath, Range:=Selection.Range)
Set iSh = Nothing
Application.StatusBar = "Converted from """ & sEQ & """. Undo if you need."
Call Kill(sPath)
End Sub ' ~~~ End of Code
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With the help of your source code, I can write Math Equations in my web now. Thanks a lot! Thank you very much!
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| Sign In·View Thread·PermaLink | 1.50/5 |
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If you want to build it for yourself, you'll need the project from
http://www.shitalshah.com/dev/eq2img_all.zip
but with gifsave.c from http://www.forkosh.com/mimetex.zip
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Hello,
do you have an solution to create the image in a winform app directly to a stream or an Image without saving a temp File?
Thank Thomas
P.S. I asked this question a time before, but now I need the functinallity urgend.
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I'm trying to opne the project with Visual Studio 2005 and I can't (the conversor fails).
Can you help me, please?
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| Sign In·View Thread·PermaLink | 1.60/5 |
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Thanks for your code but in my application I draw onto metafiles to ensure that my output is scalable.
Do you know of anyway that I can do something similar to your project here but create perhaps EMFs instead of GIFs?
Otherwise is there anyway to change your code so that the created GIF is sized to a specific size?
Thanks!
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