Send Image from Android to Datasnap Restful Server

Question

I have an Android app that send data back to a datasnap server using the RESTFul client stuff in XE2.

I have it working fine for sending standard basic data, but part of the app includes storing images the user takes.

I initially tried to use TStream, but that never got back to the server - it just seemed to hang. My current thought is to convert the byte[] of the image to a base64 string and reconvert at the datasnap end.

To convert the image to a base64 string at the Android end, I do the following:

ByteArrayOutputStream stream = new ByteArrayOutputStream();
image.compress(Bitmap.CompressFormat.JPEG, 100, stream); 
String encodedString = Base64.encode(stream.toByteArray)

encodedString then gets sent as a standard Delphi string

at the server end the code to decode is

  function Base64Decode(const EncodedText: string): TBytes;
  var
    DecodedStm: TBytesStream;
    Decoder: TIdDecoderMIME;
  begin
    Decoder := TIdDecoderMIME.Create(nil);
    try
      DecodedStm := TBytesStream.Create;
      try
        Decoder.DecodeBegin(DecodedStm);
        Decoder.Decode(EncodedText);
        Decoder.DecodeEnd;
        Result := DecodedStm.Bytes;
        SetLength(Result, DecodedStm.Size);  // add this line
      finally
        DecodedStm.Free;
      end;
    finally
      Decoder.Free;
    end;
end;

then

var
    Bytes : TBytes;
  image : TJPEGImage;
  stream : TBytesStream;
begin
  Bytes := Base64Decode(Photo);
  stream := TBytesStream.Create(Bytes);
  image := TJPegImage.Create;
  image.LoadFromStream(stream);

This creates an error in the loadFromStream method, basically the jpeg is corrupted. I'm guessing there is something wrong with either then encoding (unlikely), or converting to a delphi string then decoding to a byte[] (likely).

So this is a long winded way to ask if anyone has any suggestions on how to send an image from an Android app to a DataSnap server in Delphi XE2?

Answer 1

uses
DBXJSONCommon, 


function TServerImageMethods.ConvertJPEGToJSon(pFilePath: string): TJSONArray;
var
  AFileStream: TFileStream;
begin
  AFileStream := TFileStream.Create(pFilePath, fmOpenRead);

  Result := TDBXJSONTools.StreamToJSON(AFileStream, 0, AFileStream.Size);
end;

I convert back to a TStream with:

AFileStream := TDBXJSONTools.JSONToStream(JSONArray);

PS.: You can compress the stream with ZLIB for best performance.

Answer 2

I'm loading JPEG images, but I set the pointer at the beginning, and configure the image:

stream.Seek(0,soFromBeginning);
image.PixelFormat := jf24Bit;
image.Scale := jsFullSize;
image.GrayScale := False;
image.Performance := jpBestQuality;
image.ProgressiveDisplay := True;
image.ProgressiveEncoding := True;
image.LoadFromStream(stream);

If stream.size > 0 then
 // OK
else
 // not OK

I'll also try decoding an ANSIString, to check if it is related to the Unicode change.