Load JPEG image into a BlobField

Question

I would like load JPEG image into a blob field, is it possible? I search a lot but I don't find a clear answer.

I use this code:

var
  BlobField : TBlobField;
  Stream : TMemoryStream;
begin
  BlobField := ClientDataSet1.FieldByName('image');
  // Img is TImage and contain a JPEG image 
  Img.Picture.Graphic.SaveToStream(Stream); 
  Stream.Position := 0;
  BlobField.LoadFromStream(Stream);  // <-- Error: "Bitmap image is not valid"

I have to use bitmap image?

SOLVED: The problem was a TDBImage component on the form!. This component was linked to the field only for testing and since it work only with bitmat it give the error

related: http://stackoverflow.com/questions/18655031/how-to-display-blob-image-from-database-in-the-tadvstringgrid-with-the-help-of-d — bummi, Sep 12 '13 at 09:59
@David Heffernan the field is TBlobField and the blob type is ftBlob — Marco Andreolli, Sep 12 '13 at 10:14
@David Heffernan the table is not defined in the database! I use a ClientDataSet, the data are local — Marco Andreolli, Sep 12 '13 at 10:26
Are you sure it is `ftBlob`. If it is then it should be able to take any data. It should not care about the contents. Are you sure that the image field is not in fact `ftGraphic`? — David Heffernan, Sep 12 '13 at 10:32
@MarcoAndreolli: sorry for asking that, but is the exception message precisely *"Bitmap image is not valid"*? I ask it because once inside the stream, it´s impossible to the field to know that the stream content is an image. `TBlobField` if a general blob container, it does not know anything about image formats. — AlexSC, Sep 12 '13 at 11:00
another related including links to different duplicates: http://stackoverflow.com/questions/14726756/retrieve-image-saved-on-database — bummi, Sep 12 '13 at 11:25
@AlexSC @MarcoAndreolli this exception is occured on string `Img.Picture.Graphic.SaveToStream(Stream)`, and not on `BlobField.LoadFromStream(Stream)` — vladon, Sep 12 '13 at 13:04

vladon · Answer 1 · 2013-09-12T13:02:18.950

0

Try to use

Img.Picture.Bitmap.SaveToStream(Stream)

I.e. Bitmap property instead of Graphic

--

And if you do not want use bitmap of image, you can use TJPEGImage.

So, for example:

var
  MyJPEGImage: TJPEGImage;

[ ... ]

MyJPEGImage := TJPEGImage.Create;
MyJPEGImage.Assign(Img.Picture.Bitmap);
MyJPEGImage.SaveToStream(Stream);
Stream.Position := 0;
BlobField.LoadFromStream(Stream);

Try this.

edited Sep 12 '13 at 13:02

answered Sep 12 '13 at 09:29

vladon

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One would imagine that the idea is to store the compress JPEG data rather than uncompressed BMP – David Heffernan Sep 12 '13 at 09:30
@vladon I must have a JPEG or PNG image stored in the blob, not a Bitmap – Marco Andreolli Sep 12 '13 at 10:08
@MarcoAndreolli but you are using abstract method. Take a look at source\vcl\Vcl.Graphics.pas, procedure TGraphic.SaveToStream defined as abstract. And Img.Picture.Graphic is of type TGraphic, so, you must create TJPEGImage, load bitmap into it, and save it to stream. – vladon Sep 12 '13 at 12:53
1

@vladon The instance is not TGraphic, just the reference. It's a virtual method. The instance will be a class that does overrides and implements the abstract methods. – David Heffernan Sep 12 '13 at 13:48

score 0 · Answer 2 · answered Sep 12 '13 at 09:33

0

I use code like this

image1.Picture.LoadFromFile (filename);
fs:= TFileStream.Create (filename, fmOpenRead);
try
 blobfield.LoadFromStream (fs);
finally
 fs.Free;
end;

And having written that, I wonder what the first line is for. Presumably for displaying the image on the screen whilst saving it to the database (or more accurately, to the blobfield).

answered Sep 12 '13 at 09:33

No'am Newman

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That's the same code as in the question. How does it solve the problem? What is the problem? – David Heffernan Sep 12 '13 at 09:35
1

In the original question, it looks like the file (or memory) stream is not created (unless the 'savetostream' call does this) which might well be the problem. – No'am Newman Sep 12 '13 at 09:38
I see what you mean, but I guess that's just a transliteration error. If `Stream` was invalid then `SaveToStream` would fail. The call to `Position := 0` would fail. – David Heffernan Sep 12 '13 at 09:44
Your code don't solve the problem, It give me the same error!, I don't know if matter but I use a ClientDataSet – Marco Andreolli Sep 12 '13 at 09:55
@MarcoAndreolli: maybe the bitmap image is indeed not valid which would explain why it is not being saved. Does the image display on the screen? – No'am Newman Sep 12 '13 at 09:57
@MarcoAndreolli I asked a question. Do you have an answer? – David Heffernan Sep 12 '13 at 09:58
@No'am Newman The image are correct, I put a image on the form because I don't want load from a file. The must be a JPEG or GPG not a bitmap!. When I call "LoadFromStream" or "LoadFromFile" I give the error "Bitmap image is not valid" – Marco Andreolli Sep 12 '13 at 10:01
I found the trouble! I had put a TDBImage component (linked to the field) on the form for testing. This component work only with bitmap and so return the error "Bitmap image is not valid". Thanks @No'am Newman – Marco Andreolli Sep 12 '13 at 13:25

Load JPEG image into a BlobField

2 Answers2