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Posted 20 Sep 2006

ASP.NET Clipboard for PDF Rasterization

, 20 Sep 2006
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Use the clipboard to rasterize and/or resize a PDF file. This allows you to also save it for use as a JPG.


The first question you may ask is "Why would you ever want to use the server's clipboard to do anything?" Good question :). I came across this problem when I was trying to write a PDF parser that would rasterize the front page and save it into a Bitmap object. From here, you can save it to a file, database, etc. To do this, I was using the Adobe Acrobat COM library that comes with Adobe Acrobat 7.0. Unfortunately, they do not have a function that allows you to simply save to a file. They do, however, let you copy the image to the clipboard and then recover it in whatever format you want.


I found some great code by Jonathan Hodgson here: Generate Thumbnail Images from PDF Documents. This code was written for a C#/VB.NET Windows app, and works great if used that way. However, when I tried to use this text in the OnClick event of an ASP.NET Button control, I found that nothing was happening. Turns out, the CopyToClipboard command was working fine, because if I traced through, I could press Ctrl+v and see the image perfectly. However, when the Clipboard.GetObject method was called, it was always returning null.


After much digging and two days of work, I stumbled on the reason: the thread started for the ASP.NET application did not have the right ApartmentState to read the Clipboard class. So, here is what I did to work around this:

protected void Button_Click(object sender, EventArgs e)
     Thread cbThread = new Thread(new ThreadStart(CopyToClipboard));
     cbThread.ApartmentState = ApartmentState.STA;

protected void CopyToClipboard()
     In here, put the code that copies AND retrieves from the clipboard.
     If you use global variables, the Bitmap you populate 
     here can be used elsewhere in your code.

Final Notes

I do not recommend doing this in a multi-user environment as there is no guarantee that the user that copied to the clipboard will be the one who retrieves from it. Also, images/PDFs can be very large and the clipboard is slow.

I hope this is of some use to someone. It solved my problem, and saved me $900 by not having to buy a PDF Rasterizer control. Feel free to respond, and let me know if it helped you out or if you have any questions.


This article was posted first on the telerik forums.


This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Oleg Fridman
United States United States
No Biography provided

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Comments and Discussions

GeneralRe: Not work in Win2003 server with IIS6.0 Pin
Oleg Fridman13-Nov-07 3:42
memberOleg Fridman13-Nov-07 3:42 
GeneralWatch your EULA Pin
lrosenthol26-Sep-06 11:46
memberlrosenthol26-Sep-06 11:46 
GeneralRe: Watch your EULA Pin
Oleg Fridman26-Oct-06 10:30
memberOleg Fridman26-Oct-06 10:30 
QuestionThis was right on the mark... Pin
westberg25-Sep-06 12:25
memberwestberg25-Sep-06 12:25 
Thank you Oleg for sharing what you discovered.

I also attempted to build off of the Jonathan Hodgson article. I was successful in tweaking it for my purpose which was to generate a scheduled app that would run once a night and build all of the pdf’s within a web.configed location. After watching the memory of the server trical and the cpu take a nose dive, I decided to rewrite it with a command line arg and do one file at a time, or as uploaded from staff using the Intranet. Now I was hit with a permissions thing which I could not get around without giving elevated access which I will try to avoid at all cost. I even tried to recompile as a class dll, which was unfamiliar territory for me...

I would be forever grateful if you could give more detail as to how you tackled the thumbnail generation portion from within the process. Only one person will be uploading the image so the multi user issue will not affect my current page.

Again... thank you Oleg

Best regards, Keith
AnswerRe: This was right on the mark... Pin
Oleg Fridman25-Sep-06 15:54
memberOleg Fridman25-Sep-06 15:54 

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