Getting thumbnails from non-supported images

David Cardinal

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Jan 8, 2003, 12:44:00 PM1/8/03

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Many types of images are not directly supported by GDI+ (like 16-bit
Photoshop) files, but Explorer will still correctly extract and display
their embedded thumbnails. However, the GetThumbnail method for an Image in
.NET requires that you first load the image, which isn't possible for these
non-supported types (and would be very slow!). How can I mimic the behavior
of the Explorer by just loading the thumbnail ("stamp") image from these
files? I'm using VB.NET, although if it needs to be in C++ that's okay.

Thanks!

--David Cardinal
Pro Shooters LLC

John Hornick [MS]

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Jan 13, 2003, 11:28:28 AM1/13/03

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Hi,

You could write or by interpreters for each image type. I'm sure there
are packages available which read many more file types than are supported
by GDI+. Also, you could write your own - you'd probably want to start
with a book like "Encyclopedia of Graphics File Formats".

Thanks,
- John
Microsoft Developer Support
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John Hornick [MS]

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Jan 13, 2003, 12:06:54 PM1/13/03

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Hi,

> John--Thanks for the reply. We actually have bought or written filters
> for dozens of formats. What I'm looking for though is the clever way
> that Explorer appears to get thumbnails even from files it is not able
> to fully open.
>
> For example, WinXP can not view 48-bit Photoshop files, but it does
> correctly display a thumbnail image for them in Explorer. I can't tell
> 'from the outside' if that is because it has special drivers for that
> format which only read thumbnails, or Adobe provided some code, or if
> there is some generic function for getting at these small thumbnails
> which would be useable by other XP developers.

It could be that IE is communicating with other software on the machine
to get the thumbnail via a namespace extension, or it could be that IE
has built-in code to do it. It would depend on the file type.

You might ask on a shell newsgroup about namespace extensions - that
might be the thing for which you're looking.

David Cardinal

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Jan 13, 2003, 11:57:22 AM1/13/03

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John--Thanks for the reply. We actually have bought or written filters
for dozens of formats. What I'm looking for though is the clever way
that Explorer appears to get thumbnails even from files it is not able
to fully open.

For example, WinXP can not view 48-bit Photoshop files, but it does
correctly display a thumbnail image for them in Explorer. I can't tell
'from the outside' if that is because it has special drivers for that
format which only read thumbnails, or Adobe provided some code, or if
there is some generic function for getting at these small thumbnails
which would be useable by other XP developers.

Thanks!

--David

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David Cardinal

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Jan 31, 2003, 8:00:30 PM1/31/03

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Thanks!--David

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