如何在Delphi / C++ Builder REST WebBroker中下载适用于浏览器的jpeg图像？

Question

我必须开发一个REST方法来为RAD Studio XE7中的浏览器返回jpeg文件。调用该方法时，浏览器告诉无法显示图像，因为它包含错误；我不明白为什么。

以下是方法的代码：

void TCommerMethods::DownloadImage()
{
UnicodeString Ret;
TMemoryStream *Stream;
TIdEncoderMIME *MIMEEncoder;

  Stream = new TMemoryStream;
  Stream->LoadFromFile("C:\\Temp\\MyImage.jpg");
  Stream->Position = 0;

  MIMEEncoder = new TIdEncoderMIME(NULL);
  Ret = MIMEEncoder->EncodeStream(Stream, Stream->Size);
  delete Stream;
  delete MIMEEncoder;

  GetInvocationMetadata()->ResponseContentType = "image/jpeg";
  GetInvocationMetadata()->ResponseContent = Ret;
}

我做错了什么？

Answer 1

不要对图像文件进行MIME编码。服务器应将JPG资源原封不动地写入HTTP响应。

试试这个：

void TCommerMethods::DownloadImage()
{
  TStringStream *Stream;
  String S;
  Stream = new TStringStream;
  Stream->LoadFromFile("C:\\Temp\\MyImage.jpg");
  S = Stream->DataString;
  delete Stream;
  GetInvocationMetadata()->ResponseContentType = "image/jpeg";
  GetInvocationMetadata()->ResponseContent = S;
}

Answer 2

多亏了mjn，我解决了这个问题。下面的代码运行良好。希望它能对其他人有用：

void TCommerMethods::DownloadImage()
{
TStringStream *Stream;
String S;
  Stream = new TStringStream;
  Stream->LoadFromFile("C:\\Temp\\MyImage.jpg");
  S = Stream->DataString;
  delete Stream;
  GetInvocationMetadata()->ResponseContentType = "image/jpeg";
  GetInvocationMetadata()->ResponseContent = S;
}