Re: Metainformation in JPG

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Using the System Image PropertyItem API, certainly is the easiest way to
work with the metadata. You can set most properties for jpg, png and tif
image files using the System Image PropertyItem API.

I have not tried to set the comment property tag specifically. There is a
way to have complete programatic control over all metadata for image files.

If you are willing to do the work, then you will need to use the shell API
to give you the IPropertySetStorage interface for the image file.

Once you have that interface then you open the storage for that file to
obtain an interface for the IPropertyStorage interface using the
FMTID_ImageProperties GUID.

This interface will allow you to read and write the individual properties
for the image.

Microsoft has published sample code to use these interfaces with C++. Check
out the MSDN documentation.

Since the API makes use of the PROPVARIANT structure with UNIONS, it is
difficult to code with c# and vb.

It is much easier to code for COM Interfaces with c++ than with c# and vb.



"Laurent Bugnion" <zaehlerweg@xxxxxxxxxxxxxxxx> wrote in message
news:%23ltlLGx5GHA.3836@xxxxxxxxxxxxxxxxxxxxxxx
Hi,

I am looking at a way to embed versioning metainformation in different
image types. Since I program for the web, I want to handle PNG, GIF and
JPG. For the two first types, I found out that Image.PropertyItem allows
me to read (and hopefully write) the kind of metainformation I want.
Unfortunately, it doesn't seem to work for JPG. However I know that JPG
have a "comment" field, which would be exactly what I need.

Can anyone tell me how to programatically access the "comment" field in a
JPG image?

Thanks a lot,
Laurent.


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