Show SQLite BLOB in TDBImage box?
lazarus / 16-Databases

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Elmug · 2012-07-15 10:10

I spent the whole day trying to figure out how to show the BLOB image
from  the TDBGrid of a SQLite3 database table onto a TDBImage box.

The grid field shows (blob) and the two rows in the database do
contain each an image.

At Object Inspector, I have the Datasource of the TDBImage same as the
one for the grid, which displays the text data correctly, Datasource1,
and the DataField to Pic which is the name of the column.

One of the images is .bmp and the other is JPEG.

If I open the database in the SQLite3 administrator, I can verify the
pictures are there, and see them.

I would appreciate some help on this, on the best the way to do it.

I thought that setting the DataSource to DataSource 1, and the
DataField = Pic (the name of the table column with the BLOB), would be
sufficient, when of course the database is connected together and the
grid is working. Is this so? If not, why? How to resolve it?

P.S. With code I can get the TDBImage box to load images from from
file.
       But I need to load them from the column's field.

Thanks!

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howardpc · 2012-07-15 11:36

I think you should create a TGraphicField, and point it to the correct
datasource and datafield, and set your
TDBImage1.Picture.Bitmap (or TDBImage1.Picture.Jpeg) to the field's
Value.
However storing images in a single database in two different formats
is asking for trouble.

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Elmug · 2012-07-16 08:10

Quote from: howardpc on July 15, 2012, 01:36:13 pmI think you should
create a TGraphicField, and point it to the correct datasource and
datafield, and set your
TDBImage1.Picture.Bitmap (or TDBImage1.Picture.Jpeg) to the field's
Value.
However storing images in a single database in two different formats
is asking for trouble.

Howardpc, I tried your suggeston and variations I can think of, but no
success yet.

How would you set the TDBImage1.Picture.Bitmap (or
TDBImage1.Picture.Jpeg)  to the field's Value?

Thanks for helping.

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howardpc · 2012-07-16 12:44

Are you able to provide the database file here?

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Elmug · 2012-07-16 22:25

Howardpc,

It's an SQLite3 database with one table with only two columns.

Colum1 is integer called Column1.
Column2 is blob called Pic.

I have two rows in it, and each Pic column has a JPEG image, a typical
3 megapixel photo from an average camera.

Thanks for helping!

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Lacak2 · 2012-07-19 08:43

I repeat here answer from other thread:

There may be problem if you will use TDBImage for handling stored
BLOB.
TDBImage stores in the begining of image data file extension, which
uses later to recognize type of stored image (BMP, GIF, JPEG or so).

This can confuse other 3rd party applications which f.e. expect only
JPEG data without any "introducer".

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Joe · 2013-06-04 22:55

As Lacak2 said, the problem may, that the TBDImage implementation puts
/ expects "Picture.Graphic.GetFileExtensions" into/from the stream and
for that reason the saved data becomes incompatible to other tools
(like pgAdmin or LibreOffice Base et cetera). I think, Delphi does not
save information about the file type (see also http://wiki.lazarus.fre
epascal.org/Lazarus_1.2.0_release_notes#TDBImage).

I'd made my own Load/Save methods without that FileExtensions (saving
the raw filedata of the imagefiles into the blob stream like Delphi
do) and it works. Tested with MySQL, PostgreSQL and SQLite3 using
Zeos7.
(See also http://bugs.freepascal.org/view.php?id=24539.)

Code: [Select]procedure TJoeDBImage.UpdateData(Sender: TObject);
  var stream: TStream;
  begin
  if Empty then
    begin
    FDataLink.Field.Clear;
    end
  else begin
    stream :=
FDataLink.DataSet.CreateBlobStream(FDataLink.Field,bmwrite);
    try
      Picture.Graphic.SaveToStream(stream);
    finally
      stream.Free;
      end;
    end;
  end;

procedure TJoeDBImage.LoadPicture;
  var stream: TStream;
  begin
  if not Assigned(Field) or not (Field is TBlobField) or not
Field.IsBlob or Field.IsNull then
    begin
    Picture.Clear;
    Exit;
    end;
  stream:=DataSource.DataSet.CreateBlobStream(Field, bmRead);
  if (stream=Nil) or (stream.Size=0) then
    begin
    stream.Free;
    Picture.Clear;
    Exit;
    end;
  try // Catch all Exceptions. If the picture cannot load, then I
don't want to raise exceptions here
    Picture.LoadFromStream(stream);
  except end;
  stream.Free;
  end;