Verwirrung um TImage und den DPI Wert

[DelphiSpass]

Mit EncoderParameters hats geklappt
Nun kann ich die Auflösung und die Compression Rate einstellen (jedenfalls beim jpeg hatte ich Letzteres gebraucht).

Delphi-Quellcode:

function TFPrintOptions.SaveImageDPI(const vstrImagePath: String; const vpntImage: TPicture; const dpiResolution: Single = 300.0; const compressionQuality: Integer = 100): Boolean;
//save bmp/png/jpeg/tiff with DPI information, jpeg with compression level
var
  strDateiendung: string;
  pntBitmap: TBitmap;
  Bitmap: TGPBitmap;
  clsidEncoder: TGUID;
  EncoderResult: Integer;
  EncoderParameters: TEncoderParameters;
  QualityUL: ULONG;
  IsJpeg: Boolean;

  function GetEncoder(const AFileExt: string; out pClsid: TGUID): Integer;
  begin
    Result := -1;
    if AFileExt = '.BMP' then
    begin
      Result := GetEncoderClsid('image/bmp', pClsid)
    end
    else if AFileExt = '.PNG' then
    begin
      Result := GetEncoderClsid('image/png', pClsid)
    end
    else if (AFileExt = '.TIF') or (AFileExt = '.TIFF') then
    begin
      Result := GetEncoderClsid('image/tiff', pClsid)
    end
    else if (AFileExt = '.JPG') or (AFileExt = '.JPEG') then
    begin
      Result := GetEncoderClsid('image/jpeg', pClsid);
      IsJpeg := True;
    end;
  end;

begin
  Result := False;
  pntBitmap := TBitmap.Create;
  QualityUL := compressionQuality; //1...100
  try
    try
      pntBitmap.Assign(vpntImage);
      Bitmap := TGPBitmap.Create(pntBitmap.Handle, pntBitmap.Palette);
      try
        Bitmap.SetResolution(dpiResolution, dpiResolution);
        strDateiendung := UpperCase(ExtractFileExt(vstrImagePath));
        EncoderResult := GetEncoder(strDateiendung, clsidEncoder);
        if EncoderResult >= 0 then
        begin
          if IsJpeg and (QualityUL > 0) and (QualityUL <=100) then
          begin
            EncoderParameters.Count := 1;
            EncoderParameters.Parameter[0].Guid := EncoderQuality;
            EncoderParameters.Parameter[0].Type_ := EncoderParameterValueTypeLong;
            EncoderParameters.Parameter[0].NumberOfValues := 1;
            EncoderParameters.Parameter[0].Value := @QualityUL;
            Result := Bitmap.Save(vstrImagePath, clsidEncoder, @EncoderParameters) = TStatus.Ok;
          end else begin
            Result := Bitmap.Save(vstrImagePath, clsidEncoder) = TStatus.Ok;
          end;
        end;
      finally
        Bitmap.Free;
      end;
    except
      on E: Exception do
      begin
        raise Exception.Create('Error at saving Graphic File ' + vstrImagePath + ': ' + E.ClassName + ': ' + E.Message);
      end;
    end;
  finally
    pntBitmap.Free;
  end;
end;