Blobs and TPicture
lazarus / 16-Databases

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TRNelson · 2016-03-26 15:32

I have a small snippet of code that loads a picture file and stores it
in a Blob in a table.

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
SQLQuery1.SQL.Text:= 'insert into Photos (PhotoID, FileName, Content)
values (:PhotoID, :FileName,
:Content)';SQLQuery1.ParamByName('PhotoId').AsInteger   :=
cntr;SQLQuery1.ParamByName('FileName').AsString   :=
Info.Name;SQLQuery1.ParamByName('Content').LoadFromFile(FName,
ftBlob);SQLQuery1.ExecSQL;SQLTransaction1.Commit;
It works well and does the job. 

I would like to change the code so that the picture data comes from a
TPicture object instead.  I could write the TPicture to a temporary
file and reuse the code but that is pretty inefficient and I would
rather extract the data directly from TPicture without having to
resort to an intermediate file.

I can't find an elegant way of doing this.  All suggestions are
welcomed!

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Leledumbo · 2016-03-26 16:04

There's no direct way as far as I can find. You can use memory stream
as intermediate storage, at least it won't suffer from disk I/O
latency.

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TRNelson · 2016-03-26 16:47

Quote from: Leledumbo on March 26, 2016, 05:04:34 pmThere's no direct
way as far as I can find. You can use memory stream as intermediate
storage, at least it won't suffer from disk I/O latency.
That's what I thought as well.  The picture is already loaded in a
TPicture.  Time to do some research on memory streams.

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TRNelson · 2016-03-26 17:30

Well, that turned out to be a lot easier than I thought it would be. 
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
Thumbnail.SaveToStream(MyStream);MyStream.Position :=
0;Image1.Picture.LoadFromStream(MyStream); I am continually surprised
on how feature rich this system is.  It is a far more sophisticated
than what I used to use 40 years ago. Fortran and S/360 Assembly
language on punch cards.

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Zath · 2016-04-11 19:42

Is position the actual physical position of an image file in a
directory ?

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howardpc · 2016-04-11 21:21

No, Position is a stream property, a pointer to a location somewhere
within the entire length of the stream (for streams where Length makes
sense) where the next stream read/write will take place.
To load a picture you want to begin at Position zero, right at the
beginning of the stream (otherwise you would fail to read the initial
bytes).

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Zath · 2016-04-12 00:07

Thank you howard.