Saving and loading jpeg images to database not working DELPHI - database

Question

I'm trying to make a program that saves images in a database. I've pulled together some info on the net and wrote up code that I think is supposed to work, but fails in a completely unique way on either side (the saving and the loading).
Here's my code, could you tell me what I'm doing wrong?
Load from Database, gives me a memory address access violation error:
procedure TfrmMain.btnAddPickT4Click(Sender: TObject);
var
S : TMemoryStream;
ikode : integer;
begin
if cbxDeelnemerT4.ItemIndex < 0 then
begin
MessageDlg('Kies asseblief ''n deelnemer!',mtInformation,[mbOK],1);
Exit;
end;
if OpenPictureDialog1.Execute then
if FileExists(OpenPictureDialog1.FileName) then
Image1.Picture.LoadFromFile(OpenPictureDialog1.FileName)
else
MessageDlg('Die lêer bestaan nie!',mtError,[mbOK],1);
ikode := cbxDeelnemerT4.ItemIndex + 1;
S := TMemoryStream.Create;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = '+inttostr(ikode);
ADOQuery1.Open;
try
Image1.Picture.Graphic.SaveToStream(S);
S.Position := 1;
ADOQuery1.Insert;
TBLobfield(ADOQuery1.FieldByName('Foto')).LoadFromStream(S);
finally
S.Free;
end;
end;
Saving to the database. This code doesn't give an error as such, but it just doesn't save the image to the database:
procedure TfrmMain.btnOpenProfileT4Click(Sender: TObject);
var
S : TMemoryStream;
ikode : integer;
begin
ikode := cbxDeelnemerT4.ItemIndex + 1;
S := TMemoryStream.Create;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = '+inttostr(ikode);
ADOQuery1.Open;
try
TBlobField(ADOQuery1.FieldByName('Foto')).SaveToStream(S);
S.Position := 0;
Image1.Picture.Graphic.LoadFromStream(S);
finally
s.Free;
end;
end;

Answer 1

You are calling TGraphic.LoadFromStream() but you are not initializing the TPicture.Graphic property with a valid TGraphic-derived object beforehand, so the property is likely nil, hense the crash.
Also, when saving the TPicture.Graphic to the TMemoryStream, you are skipping the first byte of the graphic when saving it to the DB. All of the bytes are important, so do not skip any of them.
Assuming your images are specifically JPEGs and nothing else (your saving code is not restricting the file type), then try this instead:
procedure TfrmMain.btnAddPickT4Click(Sender: TObject);
var
S : TMemoryStream;
ikode : integer;
begin
if cbxDeelnemerT4.ItemIndex < 0 then
begin
MessageDlg('Kies asseblief ''n deelnemer!',mtInformation,[mbOK],1);
Exit;
end;
if not OpenPictureDialog1.Execute then
Exit;
Image1.Picture.LoadFromFile(OpenPictureDialog1.FileName);
if not (Image1.Picture.Graphic is TJpegImage) then
raise Exception.Create('Sorry, only JPG images can be saved in the DB');
ikode := cbxDeelnemerT4.ItemIndex + 1;
S := TMemoryStream.Create;
try
Image1.Picture.Graphic.SaveToStream(S);
S.Position := 0;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = '+IntToStr(ikode);
ADOQuery1.Open;
ADOQuery1.Insert;
try
TBlobField(ADOQuery1.FieldByName('Foto')).LoadFromStream(S);
ADOQuery1.Post;
except
ADOQuery1.Cancel;
raise;
end;
finally
S.Free;
end;
end;
uses
..., Jpeg;
procedure TfrmMain.btnOpenProfileT4Click(Sender: TObject);
var
S : TMemoryStream;
ikode : integer;
Jpg: TJPEGImage;
begin
ikode := cbxDeelnemerT4.ItemIndex + 1;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = ' + IntToStr(ikode);
ADOQuery1.Open;
S := TMemoryStream.Create;
try
TBlobField(ADOQuery1.FieldByName('Foto')).SaveToStream(S);
S.Position := 0;
Jpg := TJPEGImage.Create;
try
Jpg.LoadFromStream(S);
Image1.Picture.Assign(Jpg);
finally
Jpg.Free;
end;
finally
S.Free;
end;
end;
But if your images can be other formats besides JPEG, then you need to store the image type in the DB as well so that you can read it back and instantiate the correct TGraphic class type (TBitmap, TJpegImage, TGifImage, TPNGImage, etc) to handle it as needed, eg:
procedure TfrmMain.btnAddPickT4Click(Sender: TObject);
var
S : TMemoryStream;
ikode : integer;
begin
if cbxDeelnemerT4.ItemIndex < 0 then
begin
MessageDlg('Kies asseblief ''n deelnemer!',mtInformation,[mbOK],1);
Exit;
end;
if not OpenPictureDialog1.Execute then
Exit;
Image1.Picture.LoadFromFile(OpenPictureDialog1.FileName);
ikode := cbxDeelnemerT4.ItemIndex + 1;
S := TMemoryStream.Create;
try
Image1.Picture.Graphic.SaveToStream(S);
S.Position := 0;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = '+IntToStr(ikode);
ADOQuery1.Open;
ADOQuery1.Insert;
try
// this is just an example, there are other ways to do this
if Image1.Picture.Graphic is TJPEGImage then
ADOQuery1.FieldByName('FotoType').AsString := 'jpg'
else if Image1.Picture.Graphic is TPNGImage then
ADOQuery1.FieldByName('FotoType').AsString := 'png'
else if Image1.Picture.Graphic is TGIFImage then
ADOQuery1.FieldByName('FotoType').AsString := 'gif'
else if Image1.Picture.Graphic is TBitmap then
ADOQuery1.FieldByName('FotoType').AsString := 'bmp'
else
raise Exception.Create('Cannot save unsupported image type to DB');
TBlobField(ADOQuery1.FieldByName('Foto')).LoadFromStream(S);
ADOQuery1.Post;
except
ADOQuery1.Cancel;
raise;
end;
finally
S.Free;
end;
end;
uses
..., Jpeg, GifImg, PngImg;
procedure TfrmMain.btnOpenProfileT4Click(Sender: TObject);
var
S : TMemoryStream;
ikode : integer;
Graphic: TGraphic;
GraphicType: String;
begin
ikode := cbxDeelnemerT4.ItemIndex + 1;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = ' + IntToStr(ikode);
ADOQuery1.Open;
S := TMemoryStream.Create;
try
TBlobField(ADOQuery1.FieldByName('Foto')).SaveToStream(S);
S.Position := 0;
GraphicType := ADOQuery1.FieldByName('FotoType').AsString;
if GraphicType = 'jpg' then
Graphic := TJPEGImage.Create
ADOQuery1.FieldByName('FotoType').AsString := 'jpg'
else if GraphicType = 'png' then
Graphic := TPNGImage.Create
else if GraphicType = 'gif' then
Graphic := TGifImage.Create
else if GraphicType = 'bmp' then
Graphic := TBitmap.Create
else
raise Exception.Create('Cannot load unsupported image type from DB');
try
Graphic.LoadFromStream(S);
Image1.Picture.Assign(Graphic);
finally
Graphic.Free;
end;
finally
S.Free;
end;
end;
With that said, you should not be accessing TBlobField directly. Use the TDataSet.CreateBlobStream() method instead, let ADO give you a TStream object that is optimized for accessing ADO blob data, eg:
procedure TfrmMain.btnAddPickT4Click(Sender: TObject);
var
S : TStream;
ikode : integer;
begin
if cbxDeelnemerT4.ItemIndex < 0 then
begin
MessageDlg('Kies asseblief ''n deelnemer!',mtInformation,[mbOK],1);
Exit;
end;
if not OpenPictureDialog1.Execute then
Exit;
Image1.Picture.LoadFromFile(OpenPictureDialog1.FileName);
ikode := cbxDeelnemerT4.ItemIndex + 1;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = '+IntToStr(ikode);
ADOQuery1.Open;
ADOQuery1.Insert;
try
...
S := ADOQuery1.CreateBlobStream(ADOQuery1.FieldByName('Foto'), bmWrite);
try
Image1.Picture.Graphic.SaveToStream(S);
finally
S.Free;
end;
ADOQuery1.Post;
except
ADOQuery1.Cancel;
raise;
end;
end;
procedure TfrmMain.btnOpenProfileT4Click(Sender: TObject);
var
S : TStream;
ikode : integer;
Graphic: TGraphic;
begin
ikode := cbxDeelnemerT4.ItemIndex + 1;
ADOQuery1.Close;
ADOQuery1.SQL.Text := 'SELECT * FROM DEELNEMERS WHERE Kode = ' + IntToStr(ikode);
ADOQuery1.Open;
...
Graphic := ...;
try
S := ADOQuery1.CreateBlobStream(ADOQuery1.FieldByName('Foto'), bmRead);
try
Graphic.LoadFromStream(S);
finally
S.Free;
end;
Image1.Picture.Assign(Graphic);
finally
Graphic.Free;
end;
end;