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A safe array of bytes is expected as an argument
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| Hi there,
I am using the ASP to PDF component from www.asppdf.com and have an
unusual problem when displaying a blob from the database.
When there is an image stored in my SQL2000 field of type image, and I
use this:
Params = "x=337; y=408; scalex=.33; scaley=.33"
Set SigImage = Doc.OpenImageBinary(rsMotor("Photo").Value)
Page.Canvas.DrawImage SigImage, Params
The image gets drawn in the PDF and everything is fine.
If I try to create a PDF using the same record, but where the image
filed is NULL, I get this error:
Persits.PdfManager.1 error '800a002f'
A safe array of bytes is expected as an argument.
So I thought I need to check if the field isn't null before attempting
to draw it onto the canvas, so I tried this:
If LEN(rsMotor("Photo").Value) > 0 Then
'Insert Photo
Params = "x=337; y=408; scalex=.33; scaley=.33"
Set SigImage = Doc.OpenImageBinary(rsMotor("Photo").Value)
Page.Canvas.DrawImage SigImage, Params
End if
Using this with an image stored in the field gives me the same error
message, its only when the field is empty that the above code works and
doesn't draw the image on the PDF.
I also tried this:
If NOT(ISNULL(rsMotor("Photo").Value)) Then
'Insert Photo
Params = "x=337; y=408; scalex=.33; scaley=.33"
Set SigImage = Doc.OpenImageBinary(rsMotor("Photo").Value)
Page.Canvas.DrawImage SigImage, Params
End if
But still got the same error.
If I don't use any checking code, and have NULL in the image field, I
get the same error. This must be something to do with the binary
content, how can I detect if there is binary content?
Steve
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| Dooza wrote:
> Jon Paal [MSMD] wrote:
>
> Hi Jon,
> Thanks for the pointers, I like the idea of doing it in SQL, as I am
> already using a view to get the data to the page.
>
> I am still open to other ideas.
>
> Cheers,
>
> Steve
I have gone for a temporary solution, as it seems that as soon as you do
a length check or isnull check on the binary field it becomes unusable.
I have used this in my SQL view:
CASE WHEN (MC.mct_photo IS NULL)
THEN '0' ELSE '1' END AS PhotoCheck
And this on my page:
If rsMotor("PhotoCheck") = 1 Then
'Insert Photo
Params = "x=337; y=408; scalex=.33; scaley=.33"
Set SigImage = Doc.OpenImageBinary(rsMotor("Photo").Value)
Page.Canvas.DrawImage SigImage, Params
End if
Does anyone have any experience with using binary data in asp? Am I
right in thinking that the starting position has changed due to the
length check? Is there a way to reset the starting position?
Cheers,
Steve
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| Dave Anderson 2008-03-10, 6:58 pm |
| Dooza wrote:
> I have gone for a temporary solution, as it seems that as soon as you
> do a length check or isnull check on the binary field it becomes
> unusable.
> I have used this in my SQL view:
>
> CASE WHEN (MC.mct_photo IS NULL)
> THEN '0' ELSE '1' END AS PhotoCheck
>
> And this on my page:
>
> If rsMotor("PhotoCheck") = 1 Then
> 'Insert Photo
> Params = "x=337; y=408; scalex=.33; scaley=.33"
> Set SigImage = Doc.OpenImageBinary(rsMotor("Photo").Value)
> Page.Canvas.DrawImage SigImage, Params
> End if
>
> Does anyone have any experience with using binary data in asp? Am I
> right in thinking that the starting position has changed due to the
> length check? Is there a way to reset the starting position?
Rather than checking for NULL, use DATALENGTH:
http://msdn2.microsoft.com/en-us/library/ms173486.aspx
--
Dave Anderson
Unsolicited commercial email will be read at a cost of $500 per message. Use
of this email address implies consent to these terms.
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| Dave Anderson 2008-03-10, 6:58 pm |
| Dooza wrote:
>
> Hi Dave, thats a new one on me, is it SQL only, or can I use
> it in ASP/VBScript?
It's only VBScript if you can find it here:
http://msdn2.microsoft.com/en-us/library/d1wf56tt.aspx
The link I provided is Transact-SQL. I meant for you to understand that you
can use it in this manner:
SELECT
MC.mct_photo,
DATALENGTH(MC.mct_photo) AS Bytes,
...
FROM [Your Table]
This does not require a conditional evaluation in the database. You will be
using one, regardless, in your web script, so why add another?
--
Dave Anderson
Unsolicited commercial email will be read at a cost of $500 per message. Use
of this email address implies consent to these terms.
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| Anthony Jones 2008-03-10, 6:58 pm |
| "Dooza" <steveNO@SPAM.dooza.tv> wrote in message
news:%235Ob1KtgIHA.4376@TK2MSFTNGP05.phx.gbl...
> Dooza wrote:
http://databases.aspfaq.com/databas...up-my-html.html[color=darkred]
>
> I have gone for a temporary solution, as it seems that as soon as you do
> a length check or isnull check on the binary field it becomes unusable.
>
> I have used this in my SQL view:
>
> CASE WHEN (MC.mct_photo IS NULL)
> THEN '0' ELSE '1' END AS PhotoCheck
>
> And this on my page:
>
> If rsMotor("PhotoCheck") = 1 Then
> 'Insert Photo
> Params = "x=337; y=408; scalex=.33; scaley=.33"
> Set SigImage = Doc.OpenImageBinary(rsMotor("Photo").Value)
> Page.Canvas.DrawImage SigImage, Params
> End if
>
> Does anyone have any experience with using binary data in asp?
Yes
>Am I right in thinking that the starting position has changed due to the
> length check?
Yes
> Is there a way to reset the starting position?
No
When using a foward only recordset once you have consumed a BLOB you can't
consume it again. Additional you can't access standard fields once you've
started reading a BLOB.
Therefore you should use DATALENGTH as Dave suggests but you should move it
and any other fields you need to the beginning of the set of fields and
leave the photo data field as the last field. Do not attempt to use any of
the fields after consuming the photo.
Note also that DATALENGTH returns null if the field passed to it as a
parameter is null so you'll need to test that field with IsNull in VBScript
code.
--
Anthony Jones - MVP ASP/ASP.NET
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| Dave Anderson wrote:
> The link I provided is Transact-SQL. I meant for you to understand
that you
> can use it in this manner:
>
> SELECT
> MC.mct_photo,
> DATALENGTH(MC.mct_photo) AS Bytes,
> ...
> FROM [Your Table]
>
> This does not require a conditional evaluation in the database. You
will be
> using one, regardless, in your web script, so why add another?
That makes perfect sense and works perfectly too. It will also allow me
to keep an eye on the size of images in the table.
Thanks again!
Steve
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| Anthony Jones wrote:
> "Dooza" <steveNO@SPAM.dooza.tv> wrote in message
> news:%235Ob1KtgIHA.4376@TK2MSFTNGP05.phx.gbl...
> http://databases.aspfaq.com/databas...up-my-html.html
>
> Yes
>
>
> Yes
>
>
> No
>
> When using a foward only recordset once you have consumed a BLOB you can't
> consume it again. Additional you can't access standard fields once you've
> started reading a BLOB.
>
> Therefore you should use DATALENGTH as Dave suggests but you should move it
> and any other fields you need to the beginning of the set of fields and
> leave the photo data field as the last field. Do not attempt to use any of
> the fields after consuming the photo.
Putting the Blob field at the end of the table and the end of my view
was the one thing I did know about Blobs, which is why I guessed that it
was the starting position that was my problem.
I have put the Datalength field just before the Blob.
> Note also that DATALENGTH returns null if the field passed to it as a
> parameter is null so you'll need to test that field with IsNull in VBScript
> code.
Perfect, I have used a NOT ISNULL to display the blob.
Thanks again!
Steve
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| Bob Barrows [MVP] 2008-03-11, 7:57 am |
| Anthony Jones wrote:
> Note also that DATALENGTH returns null if the field passed to it as a
> parameter is null so you'll need to test that field with IsNull in
> VBScript
> code.
....or use " ... COALESCE(DATALENGTH(field),0) as fieldlength, ... " in the
sql statement.
--
Microsoft MVP - ASP/ASP.NET
Please reply to the newsgroup. This email account is my spam trap so I
don't check it very often. If you must reply off-line, then remove the
"NO SPAM"
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| Bob Barrows [MVP] wrote:
> Anthony Jones wrote:
>
> ...or use " ... COALESCE(DATALENGTH(field),0) as fieldlength, ... " in the
> sql statement.
So this basically checks if the datalength is null, and if it is, uses 0
instead, if its not it uses the datalength... I am starting to like
Coalesce more and more. In my ASP I would then check for 0 instead of NULL.
I am currently testing for null, is there any performance benefits to
using the above, or should I stick with what I have working at the moment?
Steve
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| Bob Barrows [MVP] 2008-03-11, 7:57 am |
| Dooza wrote:
> Bob Barrows [MVP] wrote:
>
> So this basically checks if the datalength is null, and if it is,
> uses 0 instead, if its not it uses the datalength... I am starting to
> like Coalesce more and more. In my ASP I would then check for 0
> instead of NULL.
?
You should still check for 0 after checking for Null. The field could
contain a zero-length string ...
> I am currently testing for null, is there any performance benefits to
> using the above, or should I stick with what I have working at the
> moment?
It avoids having to do two checks in the vbscript code. Now all you have to
check for is 0.
--
Microsoft MVP - ASP/ASP.NET
Please reply to the newsgroup. This email account is my spam trap so I
don't check it very often. If you must reply off-line, then remove the
"NO SPAM"
| |
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| Bob Barrows [MVP] wrote:
> Dooza wrote:
>
> ?
> You should still check for 0 after checking for Null. The field could
> contain a zero-length string ...
>
> It avoids having to do two checks in the vbscript code. Now all you have to
> check for is 0.
Of course, I should have been checking for empty but not null as well.
Your solution is working nicely.
Thank you Bob!
Steve
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| Dave Anderson 2008-03-13, 3:56 am |
| "Anthony Jones" wrote:
> Note also that DATALENGTH returns null if the field passed
> to it as a parameter is null so you'll need to test that
> field with IsNull in VBScript code.
Only if you care about the difference between a zero-byte image and a null.
Otherwise, this type of construction is fine:
If RS.Fields("Bytes") > 0 Then ...
--
Dave Anderson
Unsolicited commercial email will be read at a cost of $500 per message. Use
of this email address implies consent to these terms.
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