C / C++ / MFC

24 Feb '13 - 17:55

I'm trying to display an image from a stream data.
But there is no image when getting image::from stream.
It's my source code:

IStream* pstream = NULL;
	if(SUCCEEDED(CreateStreamOnHGlobal(NULL, TRUE, &pstream)))
	{
		
		ULONG lreal = 0;
 
		pstream->Write(chIncomingDataBuffer, iEnd, &lreal );
		if(pstream!= NULL)
		{
		
		MessageBox(hWnd,
						" Stream is OK",
						"Connection strt",
						MB_ICONINFORMATION|MB_OK);
		
		}
		Image* image =Image::FromStream(pstream);
		if(image)
		{
		
		RECT rect;
 
			::GetWindowRect(hWnd, &rect);
			Graphics graphics(hWnd);
			graphics.DrawImage(image, 0, 0, rect.right-rect.left, rect.bottom-rect.top);
	
		}
		else
		{
		
		MessageBox(hWnd,
						"No image is written",
						"Connection strt",
						MB_ICONINFORMATION|MB_OK);
		
		
		}
		if(image)
			delete image;
		image = NULL;
		if(pstream)
			pstream->Release();
		pstream = NULL;
	
	}

There is no image from data. Can anyone help me in this?
Thanks!

24 Feb '13 - 18:58

I have never tried doing it this way, but it looks like you took the sample from here[^], removed some stuff to make it simpler and changed it to write directly to your generic IStream object. I am not sure I like the whole thing, but it is kind of an interesting approach - if it works.

You do not show how you acquire the data that is stored in chIncomingDataBuffer. Are you sure this buffer contains an entire image?

I don't know if it is going to work, but right after you write the data to your pstream, its internal position will be pointing to the end of the data you just wrote. Try calling Seek() in order to change it to point to the start of the data.

Soren Madsen

"When you don't know what you're doing it's best to do it quickly" - Jase #DuckDynasty

Re: Displaying Image from stream

24 Feb '13 - 19:05

I checked for an image of a particular data bytes then read it and wrote the code like this..

int iff2 = 2970;
	
	iBufferLength = iSpaceRemaining = sizeof(chIncomingDataBuffer);
	iEnd = 0;
	iSpaceRemaining -= iEnd;
 
	iBytesRead = recv(Socket, chIncomingDataBuffer+iEnd, iSpaceRemaining, 0);
	
	iEnd+=iBytesRead;	
	 if(iEnd ==iff2)
	{
	
 

		MessageBox(hWnd,
						"Image  is written ok",
						"Connection strt",
						MB_ICONINFORMATION|MB_OK);
 

	IStream* pstream = NULL;

In starting if I'm trying to write an image using fwrite then its ok with exact bytes data.
But on stream, its showing some data in stream but not loading any image.

24 Feb '13 - 19:10

Ok. Let me know what happens when you call Seek() on `pstream` after writing the data. Soren Madsen "When you don't know what you're doing it's best to do it quickly" - Jase #DuckDynasty
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24 Feb '13 - 19:53

I added code for Seek() method but problem is same. ULONG lreal = 0; LARGE_INTEGER liBegining = { 0 }; if(S_OK && pstream) { pstream->Write(chIncomingDataBuffer, iEnd, &lreal ); pstream->Seek(liBegining, STREAM_SEEK_SET, NULL); this is the added code. But there is nothing.
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24 Feb '13 - 20:18

Wait a second. I see that you changed the code. You have a bug in `if(S_OK && pstream)`. The value of `S_OK` is zero, so in the code above you are not not going to do the `Write()` and the `Seek()`. Soren Madsen "When you don't know what you're doing it's best to do it quickly" - Jase #DuckDynasty
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24 Feb '13 - 20:28

Yes i also get this., S_OK is zero. But If I'm removing this then pstream is having some value. Is there any problem with CreateStreamOnHGlobal()? and one more thing,, as I got I can't draw anything outside paint event if I'm limited to GDI+.
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24 Feb '13 - 21:31

It seems this is not an easy fix, so let me ask you a couple of things. - Do you have to use the `Image` and `Graphics` stuff? - What is the format of your images (BMP, JPG, etc.)? - Are you going to be drawing anything on top of your image? Soren Madsen "When you don't know what you're doing it's best to do it quickly" - Jase #DuckDynasty
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24 Feb '13 - 21:53

-I'll have to recv some data on winsock socket and then display that on screen. I'm using Image and Graphics it for ease. -Its BMP -No nothing on top of my image. -> I'll have to recv the bytes and display image data on screen without saving it first.
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