Issue in downloading an image in Delphi

Question

I am writing an image downloader software. But I have problem to download some images such as:

https://books.google.com/books/content?id=8_pCYmpCu6UC&pg=PT4&img=1&zoom=3&hl=en&bul=1&sig=ACfU3U10JF_yd0n7gvCllBts88O_ufTWxA&w=1280

You can check it in your browser (You should see a page with 1.Introduction title. If you could not see, it is related to your region restriction. Using US proxy would solve it).

I'm using Delphi 10.3 update 2 in Win 10. My project is 32 version.

1-I used TIdHttp to download the file but I got another image (An Image with this content: "Image not available").

procedure DownloadeImage(FURL, FFileName :string);
var
  HTTPClient: TIdHTTP;
  FileStream: TFileStream;
begin
  try
    HTTPClient := TIdHTTP.Create;
    HTTPClient.HandleRedirects := True;
    HTTPClient.AllowCookies := True;
    //HTTPClient.IOHandler := TIdSSLIOHandlerSocketOpenSSL.Create(nil);
    //(HTTPClient.IOHandler as TIdOpenSSLIOHandlerClient).Options.VerifyServerCertificate := False;
    HTTPClient.Request.UserAgent := 'Mozilla/5.0'; //'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:12.0) Gecko/20100101 Firefox/12.0';
    HTTPClient.Request.Connection := 'keep-alive';
    try
      FileStream := TFileStream.Create(FFileName, fmCreate);
      try
        HTTPClient.Get(FURL, FileStream); //(TIdURI.URLEncode(FURL), FileStream);
      finally
        FileStream.Free;
      end;
    finally
      HTTPClient.Free;
    end;
  except
    // error handling ignored for this example
  end;
end;

2-The same result when using TNetHttpClient

procedure DownloadeImage(FURL, FFileName :string);
var
  HTTPClient: TNetHTTPClient;
  FileStream: TFileStream;
begin
  try
    HTTPClient := TNetHTTPClient.Create(nil);
    HTTPClient.HandleRedirects := True;
    HTTPClient.AllowCookies := True;
    //HTTPClient.SecureProtocols := [THTTPSecureProtocol.SSL2, THTTPSecureProtocol.SSL3, THTTPSecureProtocol.TLS1, //THTTPSecureProtocol.TLS11, THTTPSecureProtocol.TLS12];
    //HTTPClient.Accept := 'image/png, image/gif, image/jpg, image/jpeg, image/tif, image/tiff, image/bmp, //image/x-bmp;q=0.9,*/*;q=0.8';
    HTTPClient.UserAgent := 'Mozilla/5.0';
    try
      FileStream := TFileStream.Create(FFileName, fmCreate);
      try
        HTTPClient.Get(FURL, FileStream); //(TIdURI.URLEncode(FURL), FileStream);
      finally
        FileStream.Free;
      end;
    finally
      HTTPClient.Free;
    end;
  except
    // error handling ignored for this example
  end;
end;

3-But I get the goal using the following code:

URLMon.URLDownloadToFile(nil, PChar(FURL), PChar(FFileName), 0, nil)

Why?!!! I think it is related to some default value of TIdhttp and TNetHttpClient or about some SSL protocol.

Can anyone guide me?

Answer 1

According to AmigoJack comment:

It's related to the cookies. UrlMon support cookies by default, but for TIdHttp we should force it to use those.