www.pudn.com > webcam1.4.1.zip > dll.c

//Author:		Peter Parente 
//Copyright:	Licensed under the Academic Free License. See LICENSE.TXT for more details. 
// Patch from Philipp Spitzer 
 
#include  
#include  
#include "dll.h" 
 
HANDLE hEventOKToUpdate, hEventOKToGrab; 
HWND hWndC; 
LPBYTE pImage; 
DWORD dwSize; 
 
//Description: the start and end function of a DLL 
//Input: instance, reason for being called 
//Output: nothing important 
BOOL APIENTRY CALLBACK DllMain(HINSTANCE hInstance, DWORD fdwReason, PVOID pvReserved) { 
	 
	//select the proper action to execute based on the reason for being called 
	switch(fdwReason) { 
	case DLL_THREAD_ATTACH: 
		break; 
	case DLL_THREAD_DETACH: 
		break; 
	//when a process attaches to the DLL, create the events and initialize the variables 
	//for that process 
	case DLL_PROCESS_ATTACH: 
		hEventOKToUpdate = CreateEvent(NULL, TRUE, TRUE, NULL); 
		hEventOKToGrab = CreateEvent(NULL, TRUE, FALSE, NULL); 
		pImage = NULL; 
		hWndC = NULL; 
		dwSize = 0; 
		break; 
	//when a process detaches from the DLL, stop any image capturing and destroy the window; 
	//note that the window must be disconnected from the imaging device before this message 
	//is passed otherwise a DLL_THREAD_DETACH message is sent and the DLL gets stuck; 
	//the close function MUST be called before the process is detached or else a crash will 
	//occur 
	case DLL_PROCESS_DETACH: 
		capSetCallbackOnFrame(hWndC, NULL); 
		capPreview(hWndC, FALSE); 
		DestroyWindow(hWndC); 
		hWndC = NULL; 
		dwSize = 0; 
		break; 
	} 
	return TRUE; 
} 
 
//Description: gets the name of an imaging device associated with a given ID number 
//Input: digitizer ID number and a dummy string 
//Output: returns success (non-negative) or failure, digitizer name in dummy string 
EXPORT long GetDigitizer(long lID, CHAR *szName) { 
	CHAR szVer[80]; 
	CHAR szTemp[80]; 
 
	//get the name of the capture device associated with the given ID 
	if(!capGetDriverDescription (lID, szTemp, sizeof(szTemp), szVer, sizeof(szVer))) 
		return -1; 
	//copy the new device name over the dummy string provided by LabView 
	else 
		strcpy(szName, szTemp); 
 
	return 0; 
} 
 
//Description: callback function for capture preview mode 
//Input: window handle of the child window in which to draw the image, structure 
//	containing buffer data and length information (and more) 
//Output: nothing important 
LRESULT CALLBACK capFrame(HWND hWnd, LPVIDEOHDR lpVHdr) { 
 
	//indicate that it's not OK to grab 
	ResetEvent(hEventOKToGrab); 
	//wait until it's OK to update 
	WaitForSingleObject(hEventOKToUpdate, INFINITE); 
 
	//point to the current frame 
	pImage = lpVHdr->lpData; 
	dwSize = lpVHdr->dwBytesUsed; 
 
	//indicate it's OK to grab again 
	SetEvent(hEventOKToGrab); 
 
	return 0; 
} 
 
//Description: copies the current captured frame into a buffer provided 
//Input: length of the LabView buffer and LabView buffer 
//Output: returns success (non-negative) or failure 
EXPORT long Grab(long LVPictLength, unsigned char *LVPict) { 
	DWORD i, j; 
 
	//if the image previewing process has not yet begun, then don't grab anything 
	if(pImage == NULL) 
		return -1; 
 
	if(dwSize*4 != (unsigned long) LVPictLength*3) return -2; 
 
	//indicate that it's not OK to update 
	ResetEvent(hEventOKToUpdate); 
	//wait until it's OK to grab 
	WaitForSingleObject(hEventOKToGrab, INFINITE); 
 
	//copy current image into provided buffer; 
	//not working quite right, the color information 
	//is not being returned to LabView the way it used to be with the old DLL 
	//(the gray channel is saturated for some reason); probably not hard to fix 
	j = 0; 
	for(i=dwSize-1; i>2; i-=3) { 
		LVPict[j++] = (pImage[i]+pImage[i-1]+pImage[i-2])/3; 
		LVPict[j++] = pImage[i]; 
		LVPict[j++] = pImage[i-1]; 
		LVPict[j++] = pImage[i-2]; 
	} 
 
	//indicate it's OK to update again 
	SetEvent(hEventOKToUpdate); 
	return 0; 
} 
 
//Description: sets up an imaging device for capture operations 
//Input: digitizer ID number and a dummy string 
//Output: returns success (non-negative) or failure 
EXPORT long SetUp(long driver, long width, long height){ 
 
	//reset the image and size variables 
	pImage = NULL; 
	dwSize = 0; 
 
	//make sure we don't already have a window 
	if(hWndC == NULL) { 
		//create the capture window, the window is currently being draw in the top left corner 
		//because the buffer is filled with nothing if it is not being drawn on the screen; 
		//only a window size of 1x1 is needed to get this to work 
		hWndC = capCreateCaptureWindow(TEXT("Webcam Capture Window"), WS_CHILD | WS_VISIBLE, 0, 0, 
			1, 1, GetDesktopWindow(), 0);  
	} 
 
	//connect the selected driver to the window 
	if(!capDriverConnect(hWndC, driver)) { 
		DestroyWindow(hWndC); 
		return -1; 
	} 
 
	//create a frame capture callback function 
	if(!capSetCallbackOnFrame(hWndC, capFrame)) { 
		capDriverDisconnect(hWndC); 
		DestroyWindow(hWndC); 
		return -1; 
	} 
 
 
	//begin previewing 
	capPreviewRate(hWndC, 66); 
	if(!capPreview(hWndC, TRUE)) { 
		capDriverDisconnect(hWndC); 
		DestroyWindow(hWndC); 
		return -1; 
	} 
 
	return 0; 
} 
 
//Description: disconnects a capture window from a capture device 
//	must be called before a process is dettached from the DLL 
//Input: none 
//Output: none 
EXPORT void Close(void) { 
	capDriverDisconnect(hWndC); 
} 
 
//Description: shows a dialog box with web cam format options in it 
//	not yet implemented because not sure which dialogs should be shown for given values 
//functions to call are commented out below 
//Input: the dialog to show 
//Output: none 
EXPORT void ShowDialog(long whichDialog) { 
	if(whichDialog==0) { 
		capDlgVideoFormat(hWndC); 
	} 
	else if(whichDialog==1) { 
		capDlgVideoDisplay(hWndC); 
	} 
}