DBImage with bitmap? - delphi

Question

I am currently trying to read an Image from a MS Access database that has an OLE Object field and contains a valid bitmap (for test purposes, I created a image using MS Paint and saved it in 24bit bmp).
I am linking to this via DBGrid. In theory everything should work good and it should show the image, however I am getting a: "bitmap image not valid" error. I can understand if this is a JPEG and not .bmp, but that isn't the case. So my question is, what is wrong?
I dont necessarily have to use a DBImage, a normal TImage will also do just fine (might even be more preferable), but I'm not sure on how to assign a TImage to an OLE Object field in a MS Access Database. I Have tried, to no avail:
//Select photo from Image field
Image1.Picture := ADOTable1['Image'];
I've read most of the articles, such as about.com etc, regarding this matter, but still don't get any good results.
Any help would be greatly appreciated!
UPDATE: This worked for me:
Add to USES clause : JPEG, ADODB, DB
function JpegStartsInBlob
(PicField:TBlobField):integer;
var
bS : TADOBlobStream;
buffer : Word;
hx : string;
begin
Result := -1;
bS := TADOBlobStream.Create(PicField, bmRead);
try
while (Result = -1) and
(bS.Position + 1 < bS.Size) do
begin
bS.ReadBuffer(buffer, 1);
hx:=IntToHex(buffer, 2);
if hx = 'FF' then begin
bS.ReadBuffer(buffer, 1);
hx:=IntToHex(buffer, 2);
if hx = 'D8' then Result := bS.Position - 2
else if hx = 'FF' then
bS.Position := bS.Position-1;
end;
end;
finally
bS.Free
end;
end;
procedure TfrmOne.btnShowImageClick(Sender: TObject);
var
bS : TADOBlobStream;
Pic : TJPEGImage;
begin
bS := TADOBlobStream.Create(table1.FieldByName('Photo') as TBlobField, bmRead);
bS.Seek(JpegStartsInBlob(table1.FieldByName('Photo') as TBlobField),
soFromBeginning);
Pic := TJPEGImage.Create;
Pic.LoadFromStream(bS);
frmOne.Image1.Picture.Graphic := Pic;
Pic.Free;
bS.Free;
end;

Answer 1

what would return ADOTable1['Image'] ?
i don't like FieldVallues property u use, for you don't know the actual type and cannot control things using type checking.
I guess you'd better use Data.DB.TDataSet.FieldByName
The very type of TField object would hint you the kind of data it contains.
I don't know about Microsoft Jet (database engine of Excel and Access), but i think it stores raw BMP file data and some link to Paint application (or Gimp, or Photoshop, or whatever used to edit BMP) Kinf of TBlobField i think.
http://support.microsoft.com/kb/205635/en-us - this shows a snippet how to save file from OLE filed.
try to find a way to save field content into TFileStream.
Check that created file is really BMP file.
After that save blob into TMemoryStream and TBitmap.LoadFromStream
consider Data.DB.TBlobField.SaveToStream, Data.DB.TField.AsBytes
One more snippet from docs - explore those classes if u can use them
"Use TADOBlobStream to access or modify the value of a BLOB or memo field in an ADO dataset. BLOB fields are represented by TBlobField objects and descendants of TBlobField such as TGraphicField and TMemoField."
As resume:
1) get the type of data - ADOTable1.FieldByName.ClassName
Read about it, which methods properties would allwo u to get the data
2) try to save the data into file and analyze what is it
3) try to save that data into stream and re-use for loading picture