如何使用WIN32和C ++通过套接字发送HBITMAP？

Question

I have created an application where I am required to send the cropped part of an image over a Socket. I have cropped the image using StretchBlt(), I am also able to display and save the cropped image to a bitmap file.

Next, I want to send this cropepd image over a Socket connection. The connection between socket is established, My problem is how to send/ receive this image over Socket since send() and recv() functions require a char *.

One idea, is if I select the HBITMAP to a memDC object than can I send the memDC directly to the remote socket ?

Any easier way to achieve this task?

Answer 1

You can't pass an HBITMAP (which is a HANDLE, a reference pointer in memory) to another machine. You can use the GetBitmapBits Function to transform the HBITMAP into a byte array and send this byte array using send().

On the other side, you'll have to create another compatible bitmap, and use SetBitmapBits Function after the recv().

Answer 2

Generally sending the raw memory would be a bad idea - even if you guarantee that there's always a windows machine on the other end today, it's not very flexible for the future - what if you want to change to a different platform, or even start using .NET over plain win32?

What I'd recommend doing is saving the cropped image out to a .bmp file, then sending the file over the socket like any other. That way you have maximum flexibility for what you're doing.

Unfortunately, if you're working in C++/win32 outputting a bitmap is a bit of a nightmare. Here's the code to output a bitmap that I knocked together based on a few sources - it uses some of our class members, but you should be able to figure out how to plug in the right values there.

http://pastebin.com/gLw7ykMU

Hope this helps!