After dealing with Base64 images now I have a function that can convert PNG

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After dealing with Base64 images now I have a function that can convert PNG,
last lines are:

Img.Picture.LoadFromStream(MemoryStream);
Bmp.Assign(Img.Picture.Graphic);

Where the MemoryStream var is the decoded data from string. Now make it work for sure I have to save it as file Bmp.SaveToFile(); But why I cannot simply return:

Result := Bmp ???

If I do that, I get no error, but the image won't show.

Function returning is a TBitmap type.

Comments

  1. Lars FosdalAugust 17, 2018 at 9:13 AM

    Does calls that measure size / bit'edness / encoding / etc of the bmp - work ok?

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  2. Magno LimaAugust 17, 2018 at 9:27 AM

    Lars Fosdal No. My lack of understanding says that if I am loading from the memory stream, assign to a TBitmap object (Bmp) it is already a valid one, or should. Really don't know how to solve that, seems to be very easy but it is not

    ReplyDelete
  3. Achim KalwaAugust 17, 2018 at 9:41 AM

    Show your code.

    ReplyDelete
  4. Andrea RaimondiAugust 17, 2018 at 9:56 AM

    Reset the original stream's position to zero. It's caught me off guard so many times.

    ReplyDelete
  5. Magno LimaAugust 17, 2018 at 2:29 PM

    Achim Kalwa Here code, I don't want to need to save and load it:

    function ImgBase64ToBitmap(FileName, sBase64: AnsiString): TImage;
    var
    MS: TMemoryStream;
    Decode: TIdDecoderMIME;
    Img: TImage;
    begin
    Img := TImage.Create(nil);
    MS := TMemoryStream.Create;

    try
    Decode := TIdDecoderMIME.Create;
    try
    Decode.DecodeBegin(MS);
    Decode.Decode(sBase64);
    Decode.Decode(MS);
    Decode.DecodeEnd();

    MS.Position := 0;
    Img.Picture.LoadFromStream(MS);
    MS.Position := 0; // dahh
    Result := Img;
    // ** I DON'T want it...
    MS.SaveToFile(Concat(FileName, '.png'));


    finally
    Decode.Free;
    end;
    finally
    MS.Free;
    Img.Free;
    end;
    end;

    ReplyDelete
  6. Magno LimaAugust 17, 2018 at 2:31 PM

    Andrea Raimondi I tried, but maybe at the incorrect place...

    ReplyDelete
  7. Magno LimaAugust 17, 2018 at 2:42 PM

    I was able to do it by changing the function to procedure and doing that:
    ImgBase64ToBitmap(FileName, sBase64: AnsiString; var MemoryStream: TMemoryStream);
    So, now I get a new parameter (MemoryStream) and the main code is like:
    MS := TMemoryStream.Create;
    ImgBase64ToBitmap('imageBase64', sImg, MS);
    ImageCode64.Picture.LoadFromStream(MS);
    MS.Free;
    But I don't know if it is a good approach, at least it's working.

    ReplyDelete
  8. Achim KalwaAugust 18, 2018 at 7:34 AM

    Magno Lima the reason why you function does not work is in the finally block: You free Img, but it is the function result. Better rename the function to CreateImageFromBase64 and do not free Img in the finally block.
    The calling code is responsible for destroying the image object.

    ReplyDelete
  9. Magno LimaAugust 18, 2018 at 1:16 PM

    Achim Kalwa So my newest version works because of that, the Img object I am passing as var parameter. Thank you for the answer.

    ReplyDelete

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