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Scott Hanselman blogged about an ArgumentException that can be thrown when loading an image with a corrupted color profile. Coincidentally, we had been unifying the exception handling for BitmapImage in the Logos 4 code that same day. These are all the exceptions we have found WPF (or WIC) to throw when loading a BitmapImage (by setting its StreamSource or UriSource property) or BitmapFrame (by calling BitmapFrame.Create).

ArgumentException

Sample Call Stack

System.ArgumentException: The image has corrupted metadata header.
 ---> System.Runtime.InteropServices.COMException (0x88982F63): Exception from HRESULT: 0x88982F63
   --- End of inner exception stack trace ---
   at System.Windows.Media.Imaging.BitmapDecoder.SetupDecoderFromUriOrStream(Uri uri,
     Stream stream, BitmapCacheOption cacheOption, Guid& clsId, Boolean&
     isOriginalWritable, Stream& uriStream, UnmanagedMemoryStream&
     unmanagedMemoryStream, SafeFileHandle& safeFilehandle)
   at System.Windows.Media.Imaging.BitmapDecoder.CreateFromUriOrStream(Uri baseUri, Uri uri,
     Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
     RequestCachePolicy uriCachePolicy, Boolean insertInDecoderCache)
   at System.Windows.Media.Imaging.BitmapDecoder.Create(Stream bitmapStream,
     BitmapCreateOptions createOptions, BitmapCacheOption cacheOption)
   at System.Windows.Media.Imaging.BitmapFrame.CreateFromUriOrStream(Uri baseUri, Uri uri,
     Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
     RequestCachePolicy uriCachePolicy)
   at System.Windows.Media.Imaging.BitmapFrame.Create(Stream bitmapStream,
     BitmapCreateOptions createOptions, BitmapCacheOption cacheOption)

Cause and Workaround

An ArgumentException generally seems to be caused by a corrupted image metadata or header. Scott Hanselman suggests using BitmapCreateOptions.IgnoreColorProfile to ignore potentially corrupt color profile information; we don’t know of any workarounds for other types of corruption.

COMException

Sample Call Stack

System.Runtime.InteropServices.COMException (0x80070000): An invalid character was found in text content.
  at System.Windows.Media.ColorContextHelper.OpenColorProfile(IntPtr pProfile)
  at System.Windows.Media.ColorContext.FromRawBytes(Byte[] data, Int32 dataLength)
  at System.Windows.Media.ColorContext.FromStream(Stream stm, String filename)
  at System.Windows.Media.ColorContext.Initialize(Uri profileUri, Boolean isStandardProfileUriNotFromUser)
  at System.Windows.Media.ColorContext..ctor(PixelFormat pixelFormat)
  at System.Windows.Media.Imaging.BitmapSource.CreateCachedBitmap(BitmapFrame frame,
    BitmapSourceSafeMILHandle wicSource, BitmapCreateOptions createOptions, BitmapCacheOption
    cacheOption, BitmapPalette palette)
  at System.Windows.Media.Imaging.BitmapFrameDecode.FinalizeCreation()
  at System.Windows.Media.Imaging.BitmapFrameDecode..ctor(Int32 frameNumber,
    BitmapSourceSafeMILHandle sourceHandle, BitmapCreateOptions createOptions,
    BitmapCacheOption cacheOption, BitmapDecoder decoder)
  at System.Windows.Media.Imaging.BitmapDecoder.SetupFrames(BitmapDecoder decoder,
    ReadOnlyCollection`1 frames)
  at System.Windows.Media.Imaging.BitmapDecoder.get_Frames()
  at System.Windows.Media.Imaging.BitmapFrame.CreateFromUriOrStream(Uri baseUri, Uri uri,
    Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
    RequestCachePolicy uriCachePolicy)
  at System.Windows.Media.Imaging.BitmapFrame.Create(Uri bitmapUri, RequestCachePolicy uriCachePolicy)
  at System.Windows.Media.Imaging.BitmapFrame.Create(Uri bitmapUri)

Cause and Workaround

This particular exception was caused by an invalid system color profile (set in the Advanced tab in Color Management in Control Panel). The user with this problem got an error message when he opened that dialog, but once he reset the device profile to the system default, this COMException stopped being thrown.

Note that the exception message (“An invalid character was found”) is completely unrelated to the actual problem; the error handling logic in ColorContextHelper has a bug.

FileFormatException

Sample Call Stack

System.IO.FileFormatException: The image format is unrecognized.
 ---> System.Runtime.InteropServices.COMException (0x88982F07): Exception from HRESULT: 0x88982F07
  --- End of inner exception stack trace ---
  at System.Windows.Media.Imaging.BitmapDecoder.SetupDecoderFromUriOrStream(Uri uri,
    Stream stream, BitmapCacheOption cacheOption, Guid& clsId, Boolean& isOriginalWritable,
    Stream& uriStream, UnmanagedMemoryStream& unmanagedMemoryStream,
    SafeFileHandle& safeFilehandle)
  at System.Windows.Media.Imaging.BitmapDecoder.CreateFromUriOrStream(Uri baseUri, Uri uri,
    Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
    RequestCachePolicy uriCachePolicy, Boolean insertInDecoderCache)
  at System.Windows.Media.Imaging.BitmapImage.FinalizeCreation()
  at System.Windows.Media.Imaging.BitmapImage.EndInit()

Cause and Workaround

This can be caused by trying to load a file that isn’t an image. It can also be caused by loading an image from a Stream that is not at the origin. To work around this bug, see my previous blog post and the sample RebasedStream source code.

NotSupportedException

Sample Call Stack

System.NotSupportedException: No imaging component suitable to complete this operation was found.
 ---> System.Runtime.InteropServices.COMException (0x88982F50): Exception from HRESULT: 0x88982F50
  --- End of inner exception stack trace ---
  at System.Windows.Media.Imaging.BitmapDecoder.SetupDecoderFromUriOrStream(Uri uri,
    Stream stream, BitmapCacheOption cacheOption, Guid& clsId, Boolean& isOriginalWritable,
    Stream& uriStream, UnmanagedMemoryStream& unmanagedMemoryStream,
    SafeFileHandle& safeFilehandle)
  at System.Windows.Media.Imaging.BitmapDecoder.CreateFromUriOrStream(Uri baseUri, Uri uri,
    Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
    RequestCachePolicy uriCachePolicy, Boolean insertInDecoderCache)
  at System.Windows.Media.Imaging.BitmapFrame.CreateFromUriOrStream(Uri baseUri, Uri uri,
    Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
    RequestCachePolicy uriCachePolicy)
  at System.Windows.Media.Imaging.BitmapFrame.Create(Uri bitmapUri, RequestCachePolicy uriCachePolicy)
  at System.Windows.Media.Imaging.BitmapFrame.Create(Uri bitmapUri)

Cause and Workaround

This error is typically due to bad metadata in the image. Curiously, we see this error the most often on Windows 7 (and a Vista system may load the same image just fine!); maybe this is due to WIC changes in Windows 7. For images we control, opening and saving them again in Paint.NET (or some other image editing program) overwrites the bad metadata and allows WPF/WIC to load the image.

OutOfMemoryException

Cause and Workaround

If there is already memory pressure on the system (e.g., from other components in your application), and the image being loaded is very large, there may not be enough virtual address space for WIC/WPF to allocate the storage it needs to decode the bitmap. (And, sometimes, both native and managed buffers are required, which doubles memory usage!)

Setting BitmapImage.DecodePixelWidth or BitmapImage.DecodePixelHeight (to something smaller than the actual size) can dramatically reduce memory usage and allow the image to be loaded. This is especially useful if your application only needs to show a thumbnail in the UI; it’s also much more efficient than loading the original image and scaling it in XAML.

IOException / UnauthorizedAccessException

Sample Call Stack

System.IO.IOException: Cannot locate resource 'images/icon.png'.
  at MS.Internal.AppModel.ResourcePart.GetStreamCore(FileMode mode, FileAccess access)
  at System.IO.Packaging.PackagePart.GetStream(FileMode mode, FileAccess access)
  at System.IO.Packaging.PackWebResponse.CachedResponse.GetResponseStream()
  at System.IO.Packaging.PackWebResponse.GetResponseStream()
  at System.IO.Packaging.PackWebResponse.get_ContentType()
  at System.Windows.Media.Imaging.BitmapDecoder.SetupDecoderFromUriOrStream(Uri uri,
    Stream stream, BitmapCacheOption cacheOption, Guid& clsId, Boolean& isOriginalWritable,
    Stream& uriStream, UnmanagedMemoryStream& unmanagedMemoryStream,
    SafeFileHandle& safeFilehandle)
  at System.Windows.Media.Imaging.BitmapDecoder.CreateFromUriOrStream(Uri baseUri, Uri uri,
    Stream stream, BitmapCreateOptions createOptions, BitmapCacheOption cacheOption,
    RequestCachePolicy uriCachePolicy, Boolean insertInDecoderCache)
  at System.Windows.Media.Imaging.BitmapImage.FinalizeCreation()
  at System.Windows.Media.Imaging.BitmapImage.EndInit()
  at System.Windows.Media.Imaging.BitmapImage..ctor(Uri uriSource, RequestCachePolicy uriCachePolicy)
  at System.Windows.Media.Imaging.BitmapImage..ctor(Uri uriSource)

Cause and Workaround

If you’re loading an image from a file: URI, any normal filesystem-related exceptions that come from opening local files could be thrown. Or, if you’re using pack: URIs, an exception will be thrown if there’s a typo in the URI or the named resource is missing.

Summary

The BitmapImage and BitmapFrame creation functions can throw a wide variety of exception types–the list above may very well not be exhaustive (and the documentation provides no information on what else may be thrown). Since these exceptions can depend on many environmental factors (client OS, file permissions, memory pressure, etc.), code that loads bitmaps needs to anticipate failure when loading any image and gracefully handle this situation.

This post originally appeared on code.logos.com

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System.Data.SQLite is a great ADO.NET wrapper around the free SQLite embedded database library. Today we contributed two simple patches to the project.

The first patch adds support to SQLiteJournalModeEnum for the “truncate” journal mode (added in v3.6.4 of SQLite).

The second patch adds support to SQLiteException for logging the extended error information (for SQLITE_IOERR).

This post originally appeared on code.logos.com

Written by: Wes Allen

My son has Ocular Albinism.  It doesn’t slow him down much, but it does make reading a frustrating experience for him.  I’ve found his frustration disheartening because my son is a very good reader.  He has the ability to give characters voices and can work unfamiliar words out pretty well.

At our church children are given a Bible at a certain age, and our son is receiving his this year.  We assumed that we could get a large print Bible that would work for him, but on Monday we checked out the large print Bibles and found that there we wholly unsuitable for someone with my son’s sight issues.  The font was still far too small for him to read without a magnifier of some kind, and even then the paper was so thin the text on the opposite side could easily be seen – for someone who needs strong contrast, it would have made it impossible for him to read.

Three years ago he would have been out of luck, but the advent of digital readers offers my son a chance to learn to enjoy reading like everyone else in the family (which he desperately wants to do).  So my wife and I resolved that we would look for grants to help acquire an iPad for his use in school, home, and church.  Really, that wouldn’t have been a difficult task.

You may be asking, “Why an iPad?”  For a few reasons:

• It’s backlit.  The e-ink displays are nice, but they are terrible in low light and so the lit screen is a must for someone who has vision issues like my son.
• It’s out.  I would have loved to see what Android and WebOS tablets will come out – but they aren’t here yet and we have a small window to get our son reading for enjoyment.  We also will need it for school come September.
• It’s simple, he took to it immediately.
• It’s got multiple book stores.  iBooks is nice, but the book selection is terrible.  Kindle has a nice book selection but for some dumb reason they limit how big you can make the font.  Kobo isn’t a great experience, but has good font sizes and a good number of books.  B&N doesn’t have their iPad reader out yet, I expect it to be well-designed.
• Even though it’s simple, it’s multi-function.  I can set up a drop-box between him and his teachers and he can have access to lesson notes, reducing the strain looking at the board puts on his eyes.

So, those are some of the reasons.  Like I said we had committed to writing grants to acquire the device, but we didn’t have to wait that long.  In a rare AT&T late voicemail delivery #win, my mother called up shortly after we left the Christian book store and went on to other errands.  She works at a local university so I said, “Hey, while you’re on the line, do you think you could give me some leads on where to apply for educational grants?”  When my mother asked why I was looking I told her about what we wanted to do for our son and why we thought the iPad would work well for him.  She said, “You have a grant.”  I said something like, “Whubhuh?” To with my mother replied, “It’s called ‘Aunt Ann’s estate.’”

My great aunt, the last matriarch of the depression generation for our extended family passed away last year, she apparently left money to her nieces and nephews and my mom was looking for a good way to spend it.  She said, “This is what I want to do with it, go get him one.”

Now, my folks are not wealthy.  It also wouldn’t have been difficult to write a grant for the device, so I tried to balk at my mom’s generosity by nervously chuckling.  She got a bit miffed with me when I did that. Mom’s can do that.  Her offer also wasn’t some sort of impulse purchase (that’s my job).  My Aunt Ann spent her entire life in the service of others, particularly in seeing the elderly empowered rather than set aside in their later years.  She even was invited to a White House dinner once because of her work (I remember readin the invitation).  My mom wanted to do something with the money that would be in line with her aunt had lived – she insisted this was it.

One of the things I will always be thankful for in my family, both nuclear and extended, is the value of education.  My mom saw a way to see that her grandson could strive forward, and she jumped on it.  I’m very thankful.

Below is a video of our son seeing the iPad for the first time on Monday.  Before you watch it let me stress a couple of things:

• This is his iPad.  Yes, I’m a geek and it it tempting to take this with me wherever I go and play with it.  That would be a terrible thing to do with my mother’s generosity.  Yet, it’s tempting – but it’s not mine.  I’ll have to save up money for that.
• While he says, “It has my games” in the video – I have very few games on this (and some are for my wife to play after our son crashes for the night).  He likes “little metal ball” – and it’s good practice for his eye-hand coordination. This is for reading, and if he takes it into his room at night that’s all he will be allowed to do with it. He has a DsiXL for games, it was his birthday present.

So, yes, I will do some reviews on my thoughts on the iPad and it’s uses, but I’m more interested in tracking how my son uses it.  He’s very into the Winny The Pooh that comes with iBooks.  Now if iBooks would only get the Narnia books.  I got him a sample chapter of Eregon, but he said, “No, this is a book where people die – I don’t like those.”

This post originally appeared on Painfully Hopeful

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There are several occasions when it’s necessary to automatically detect the encoding that’s used by a file: perhaps your program has an “Import” feature that allows the user to open an arbitrary text file, or perhaps you need to read a HTML file and don’t have access to (or can’t trust) the Content-Type HTTP header. (For an introduction to encodings, see The Absolute Minimum Every Software Developer Absolutely, Positively Must Know About Unicode and Character Sets (No Excuses!) by Joel Spolsky.)

On U.S. English Windows, you can usually assume that the file might be encoded with UTF-8 or Windows-1252, but if you guess wrong, you might get text that looks like this:

�It�s mine,� he said.

or this:

“It’s mine,” he said.

or worst yet, this:

Unhandled System.Text.DecoderFallbackException

While it’s obviously best to know the encoding that’s used by the input you’re processing, sometimes there’s no way to know it ahead of time. In that case, there are libraries that can guess the encoding, usually based on statistical analysis of the bytes or detection of invalid byte sequences. The Mozilla project has a universal charset detector, and Microsoft has been shipping MLang, a COM component that provides code page detection through the IMultiLanguage2.DetectCodepageInIStream method since IE5.

The COM interfaces and structures we need are declared as follows (definitions taken from MLang.h in the Windows SDK):