c# - How to get binary image data from IntPtr (look alike multipart/form-data)

Question

Let's say:

byte[] bytes = new byte[1024 * 100];
Marshal.Copy(nET_DVR_XML_CONFIG_OUTPUT.lpOutBuffer, b, 0, 1024 * 100);
string responseMsg = Encoding.ASCII.GetString(bytes);
            
//so string responseMsg basically like this.
string responseMsg = @"Content-Type:multipart/form-data;boundary=MIME_boundary
--MIME_boundary
Content-Type: application/json
Content-Length:1629
{
    "requestURL":   "/ISAPI/Intelligent/FDLib/FDSearch?format=json",
    "statusCode":   1
}
--MIME_boundary
Content-Type:image/jpeg
Content-Length:20455

???? ►JFIF ☺☺☺ ? ?  ??♥rExif  (much more binary data.....)

--MIME_boundary"; //End of string

How do I get just the image binary data only? Just to make it more clear, nET_DVR_XML_CONFIG_OUTPUT.lpOutBuffer is IntPtr send by the device after I send a request through ISAPI.

Hopefully my question is clear enough to understand. I've been stuck on this problem quite a while already. Any help would be massively appreciated.

Answer 1

Your response is a Multi-part MIME message.

Your first challenge is to parse the MIME parts. Here are two good resources:

• https://docs.microsoft.com/en-us/dotnet/api/system.net.mime.contenttype.boundary

• https://www.c-sharpcorner.com/uploadfile/2b481f/processing-multipart-mime-in-asp-net-web-api/

The second MIME message part is clearly a binary .jpeg file (hence the JFIF header). You should be able to treat it as a .Net "string", and simply convert it to a byte array:

byte[] bytes = Encoding.ASCII.GetBytes(input); 

The resulting byte array is your JPEG image.

I'm not sure how much of this you already knew, or exactly where you're "stuck". But I hope this helps.