PdfScan is a simple tool for scanning pages into a PDF file. You can scan single pages from a flatbed scanner or several pages from a document feeder. The page size applies to both the scan and the page(s) added to the PDF.

I wrote PdfScan because I know I'm going to be scanning a lot of documents over the next couple of weeks. Previously I used a tool called ScanToPDF from O Imaging but their licensing pissed me off so much that I'd rather waste time reinventing the wheel than pay them for another copy.

This is a beta — it works with my scanner and my documents. There's no installer, so extract the ZIP file and run the EXE to use it. PdfScan requires the .NET 4.0 Framework. If you get an error when you run PdfScan.exe try installing .NET 4 and then run it again.

If enough people use this I'll make it a bit more friendly, add an installer and release it through Catfood. If you like it leave a comment below. If it doesn't work for you leave a comment or email me and I'll try to help.

(Update September 12, 2010: I've tided PdfScan up and released it through Catfood Software. Download from Catfood PdfScan.)

PdfScan uses PDFsharp from empira Software. Thanks chaps!

I've been going nuts trying to scan from the document feeder on my Canon imageClass MF4150. Everything worked as expected from the flatbed, no dice trying to persuade the ADF to kick in. I found some sample code but it was oriented towards devices that can detect when a document is available in the feeder. Evidently my Canon doesn't expose this and so needs to be told the source to use.

The way to do this is to set the WIA_DPS_DOCUMENT_HANDLING_SELECT property to FEEDER. You then read WIA_DPS_DOCUMENT_HANDLING_STATUS to check that it's in the right mode and initiate the scan. This did not work for toffee.

After much experimentation I discovered a solution. I had been setting device properties and then setting item properties before requesting the scan. Switching the order - item then device - made everything work.

Here's the function to scan one page:

A few notes — XImage is a type from PDFSharp. I wrote this as part of a PDF scanner that I'll post next so the scanned images are saved and then loaded into an XImage for rendering to the PDF document. The magic numbers come from WiaDef.h in the Platform SDK. If the ADF is out of pages this method sets the return image to null and eats the exception. This is because the function is called repeatedly to scan in pages until the ADF is empty if _adf is true (otherwise it grabs one image from the flatbed). 

If you've been banging your head against a wall trying to get WIA to work with a document feeder I hope this helps.

Updated 2015-05-20: Full source code at https://github.com/abfo/pdfscan

After floundering a bit with the WPF Dispatcher I've come up with a simple way to make sure an event handler executes on the UI thread without paying the overhead of always invoking a delegate.

This has the benefit (for me at least) of being very easy to remember. Hook up the event handler and then if there's a chance it could be called from a different thread wrap it using the pattern above. It's easier to read than an anonymous delegate and much faster than defining a specific delegate for the event in question.

I haven't tested the various methods to see which is the fastest yet… will get round to this at some point.

5. Validation

The metadata required to use the like button looks like this:

But the property attribute isn't valid html or xhtml. The “Open” Graph Protocol says that it's inspired by Dublin Core. DC manages to get by using the name attribute like any other meta tag - why can't Open Graph? It's not the worst problem but it just seems needlessly irksome. Facebook has published a presentation describing their design decisions. This would be great, but it's in that Lessig one word per slide style and so it's attractive but completely useless without the presenter.

4. Fragility

Facebook's documentation is frustratingly sparse. For example you need to specify the owner of the page using a Facebook ID, and once you've chosen a name for your profile this is hard to find. The information vacuum has been filled with many erroneous blog posts saying to use the name, or some number from a shared photo (the best source is http://graph.facebook.com/robert.ellison, substituting your own username). Once you've got the admin ID wrong, you can't correct it - the first admin specified is fixed forever. What happens if a site is hacked and a bad actor sets themselves up as the admin? Surely something like the Google Webmaster Tools authentication scheme could have been used instead?

3. Pages with more than one object

Describing the object being liked in the head element limits you to one object per page. For some sites this is perfect, but what about a blog where you have many posts on the home page? It would be useful to have a like button per post, pointing at the permalink for the post in question. I've worked around this by having a like button for the blog on the home page, and a like button for each post on the post pages. Not ideal. I'm using the iframe version of the gadget, possibly there's some more flexibility with the XBML variant.

2. Duplicating existing pages

Let's say you've spent the past couple of years building up a Facebook page for your site/band/blog/movie and have thousands of fans. When you click your new like button for the first time you create a whole new page. There's no way to tell the like button about the existing page or the existing page about the like button. You now have at least two pages to worry about managing and potentially many, many more. You're also starting from scratch on the ‘like’ count, so even if your brand is already popular on Facebook it's back to Billy no-mates for you.

I can't believe this won't be fixed at some point. As with admin authentication above there must be a better way to establish ownership of various objects in the social graph.

1. Vocabulary

For better or worse Facebook has the inexorable pull to start making the semantic web a reality. Given this, and that there are something like twenty-four thousand verbs in the English language it's time for more expressiveness than ‘like’. You also can't comment on the ‘liked’ item in your stream (yet) so no clarification or discussion is possible.

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Having said all that, if you enjoyed this post please click the ‘like’ button above ;)

Links

When testing out a WPF app on XP I got an unhelpful XamlParseException error report. 

I was a little puzzled because I was hooking up error reporting in App.xaml.cs:

My error handler was attempting to create a XAML window to report the error, and evidently this was bombing out as well triggering the good doctor Watson. I added a MessageBox call instead and discovered that the XamlParseException was wrapping a FileFormatException and the stack trace indicated that the problem was with setting the icon for the window. After removing the icon the app started up fine. Weird.

It turns out that WPF chokes on a compressed 256x256 icon on XP and Vista (Windows 7 seems to cope fine). Saving the icon without compression fixes the problem. I use IcoFX and you can set this at Options -> Preferences -> Options -> Compress 256x256 images for Windows Vista. Of course the consequence is that the icon is a couple of hundred kilobytes larger.

I've spent the last day learning how to use OAuth and XAuth to post to Twitter. There are rumblings that Twitter will start to phase out basic authentication later this year, and more importantly you can only get the nice “via...” attribution if you use OAuth (for new apps, old ones are grandfathered in).

I coded up my own OAuth implementation, referring to Twitter Development: The OAuth Specification on Wrox and the OAuthBase.cs class from the oauth project on Google Code. Both are great references, but both fail with multibyte characters. The problem is that each byte needs to be separately escaped. OAuthBase.cs encodes characters as ints rather than breaking out the bytes and the Wrox article incorrectly suggests using Uri.EscapeDataString(). 

Here's a method to correctly encode parameters for OAuth:

NoEncode chars is a list of the permitted characters:

An impact of this encoding is that spaces must be encoded as %20 rather than plus. I was worried that each space would end up counting as three characters towards the 140 character limit. I tested this and it isn't true, so use HttpUtility.UrlEncode() to calculate the number of characters in the post OAuthUrlEncode() or similar to actually encode post parameter.

Links

If you send email to customers it's important that you let them know where the email will come from and then use then use this address consistently. Using different email addresses is a recipe for getting trapped in spam filters. This is equally important for marketing and other messaging like bills and canceled flights.

I bring up flights because I'm flying to the UK later today and was planning to return on Sunday. British Airways' Cabin Crew is going on strike this weekend and my return flight has been canceled. Instead of sending a text message BA tried to notify me by email. This would have been fine if they used the address they've used for years, but instead they used a new address and a new domain. In fact in the process of canceling and re-booking I (eventually) got email from britishairways.com, my.ba.com, email.ba.com and pop3.amadeus.net.

Since I've had the same email address for twelve years now I get a fair amount of spam. I use SpamArrest to keep myself sane:

94.9% of my email is spam. Since I started using the service SpamArrest has eaten 482,494 messages for me. I'm far from alone in using white list based email filtering so if you want your message to get through transparency and consistency are the way to go.