الگوریتم Canny در سی پلاس پلاس قسمت 3

مرحله 3: ردیابی در امتداد لبه ها

گام بعدی در واقع این است که در امتداد لبه ها بر اساس نقاط قوت و جهت های لبه که قبلا محاسبه شده است ردیابی شود. هر پیکسل از طریق استفاده از دو تودرتو برای حلقه ها چرخه می زند. اگر پیکسل فعلی دارای قدرت شیب بیشتر از مقدار upperThreshold تعریف شده باشد، یک سوئیچ اجرا می شود. این سوئیچ توسط جهت لبه پیکسل فعلی تعیین می شود. این ردیف و ستون، پیکسل ممکن بعدی را در این جهت ذخیره می کند و سپس جهت لبه و استحکام شیب آن پیکسل را آزمایش می کند. اگر آن همان جهت لبه و  قدرت گرادیان بزرگتر از lowerThreshold را دارد، آن پیکسل به سفید و پیکسل بعدی در امتداد آن لبه آزمایش می شود. به این ترتیب هر لبه قابل توجه تیز تشخیص داده شده و به سفید تنظیم می شود در حالیکه تمام پیکسل های دیگر به سیاه تنظیم می شود.

#include "stdafx.h"
#include "tripod.h"
#include "tripodDlg.h"

#include "LVServerDefs.h"
#include "math.h"
#include <fstream>
#include <string>
#include <iostream>
#include <stdlib.h>
#include <stdio.h>


#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

using namespace std;

/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
	CAboutDlg();

// Dialog Data
	//{{AFX_DATA(CAboutDlg)
	enum { IDD = IDD_ABOUTBOX };
	//}}AFX_DATA

	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CAboutDlg)
	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	//}}AFX_VIRTUAL

// Implementation
protected:
	//{{AFX_MSG(CAboutDlg)
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
	//{{AFX_DATA_INIT(CAboutDlg)
	//}}AFX_DATA_INIT
}

void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CAboutDlg)
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
	//{{AFX_MSG_MAP(CAboutDlg)
		// No message handlers
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CTripodDlg dialog

CTripodDlg::CTripodDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CTripodDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(CTripodDlg)
		// NOTE: the ClassWizard will add member initialization here
	//}}AFX_DATA_INIT
	// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
	m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);

	//////////////// Set destination BMP to NULL first 
	m_destinationBitmapInfoHeader = NULL;

}

////////////////////// Additional generic functions

static unsigned PixelBytes(int w, int bpp)
{
    return (w * bpp + 7) / 8;
}

static unsigned DibRowSize(int w, int bpp)
{
    return (w * bpp + 31) / 32 * 4;
}

static unsigned DibRowSize(LPBITMAPINFOHEADER pbi)
{
    return DibRowSize(pbi->biWidth, pbi->biBitCount);
}

static unsigned DibRowPadding(int w, int bpp)
{
    return DibRowSize(w, bpp) - PixelBytes(w, bpp);
}

static unsigned DibRowPadding(LPBITMAPINFOHEADER pbi)
{
    return DibRowPadding(pbi->biWidth, pbi->biBitCount);
}

static unsigned DibImageSize(int w, int h, int bpp)
{
    return h * DibRowSize(w, bpp);
}

static size_t DibSize(int w, int h, int bpp)
{
    return sizeof (BITMAPINFOHEADER) + DibImageSize(w, h, bpp);
}

/////////////////////// end of generic functions


void CTripodDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CTripodDlg)
	DDX_Control(pDX, IDC_PROCESSEDVIEW, m_cVideoProcessedView);
	DDX_Control(pDX, IDC_UNPROCESSEDVIEW, m_cVideoUnprocessedView);
	//}}AFX_DATA_MAP
}

BEGIN_MESSAGE_MAP(CTripodDlg, CDialog)
	//{{AFX_MSG_MAP(CTripodDlg)
	ON_WM_SYSCOMMAND()
	ON_WM_PAINT()
	ON_WM_QUERYDRAGICON()
	ON_BN_CLICKED(IDEXIT, OnExit)
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CTripodDlg message handlers

BOOL CTripodDlg::OnInitDialog()
{
	CDialog::OnInitDialog();

	// Add "About..." menu item to system menu.

	// IDM_ABOUTBOX must be in the system command range.
	ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
	ASSERT(IDM_ABOUTBOX < 0xF000);

	CMenu* pSysMenu = GetSystemMenu(FALSE);
	if (pSysMenu != NULL)
	{
		CString strAboutMenu;
		strAboutMenu.LoadString(IDS_ABOUTBOX);
		if (!strAboutMenu.IsEmpty())
		{
			pSysMenu->AppendMenu(MF_SEPARATOR);
			pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
		}
	}

	// Set the icon for this dialog.  The framework does this automatically
	//  when the application's main window is not a dialog
	SetIcon(m_hIcon, TRUE);			// Set big icon
	SetIcon(m_hIcon, FALSE);		// Set small icon
	
	// TODO: Add extra initialization here

	// For Unprocessed view videoportal (top one)
	char sRegUnprocessedView[] = "HKEY_LOCAL_MACHINE\\Software\\UnprocessedView";
	m_cVideoUnprocessedView.PrepareControl("UnprocessedView", sRegUnprocessedView, 0 );	
	m_cVideoUnprocessedView.EnableUIElements(UIELEMENT_STATUSBAR,0,TRUE);
	m_cVideoUnprocessedView.ConnectCamera2();
	m_cVideoUnprocessedView.SetEnablePreview(TRUE);

	// For binary view videoportal (bottom one)
	char sRegProcessedView[] = "HKEY_LOCAL_MACHINE\\Software\\ProcessedView";
	m_cVideoProcessedView.PrepareControl("ProcessedView", sRegProcessedView, 0 );	
	m_cVideoProcessedView.EnableUIElements(UIELEMENT_STATUSBAR,0,TRUE);
	m_cVideoProcessedView.ConnectCamera2();
	m_cVideoProcessedView.SetEnablePreview(TRUE);

	// Initialize the size of binary videoportal
	m_cVideoProcessedView.SetPreviewMaxHeight(240);
	m_cVideoProcessedView.SetPreviewMaxWidth(320);

	// Uncomment if you wish to fix the live videoportal's size
	// m_cVideoUnprocessedView.SetPreviewMaxHeight(240);
	// m_cVideoUnprocessedView.SetPreviewMaxWidth(320);

	// Find the screen coodinates of the binary videoportal
	m_cVideoProcessedView.GetWindowRect(m_rectForProcessedView);
	ScreenToClient(m_rectForProcessedView);
	allocateDib(CSize(320, 240));

	// Start grabbing frame data for Procssed videoportal (bottom one)
	m_cVideoProcessedView.StartVideoHook(0);

	return TRUE;  // return TRUE  unless you set the focus to a control
}

void CTripodDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
	if ((nID & 0xFFF0) == IDM_ABOUTBOX)
	{
		CAboutDlg dlgAbout;
		dlgAbout.DoModal();
	}
	else
	{
		CDialog::OnSysCommand(nID, lParam);
	}
}

// If you add a minimize button to your dialog, you will need the code below
//  to draw the icon.  For MFC applications using the document/view model,
//  this is automatically done for you by the framework.

void CTripodDlg::OnPaint() 
{
	if (IsIconic())
	{
		CPaintDC dc(this); // device context for painting

		SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0);

		// Center icon in client rectangle
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// Draw the icon
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{
		CDialog::OnPaint();
	}
}

// The system calls this to obtain the cursor to display while the user drags
//  the minimized window.
HCURSOR CTripodDlg::OnQueryDragIcon()
{
	return (HCURSOR) m_hIcon;
}

void CTripodDlg::OnExit() 
{
	// TODO: Add your control notification handler code here

	// Kill live view videoportal (top one)
	m_cVideoUnprocessedView.StopVideoHook(0);
    m_cVideoUnprocessedView.DisconnectCamera();	
	
	// Kill binary view videoportal (bottom one)
	m_cVideoProcessedView.StopVideoHook(0);
    m_cVideoProcessedView.DisconnectCamera();	

	// Kill program
	DestroyWindow();	

	

}

BEGIN_EVENTSINK_MAP(CTripodDlg, CDialog)
    //{{AFX_EVENTSINK_MAP(CTripodDlg)
	ON_EVENT(CTripodDlg, IDC_PROCESSEDVIEW, 1 /* PortalNotification */, OnPortalNotificationProcessedview, VTS_I4 VTS_I4 VTS_I4 VTS_I4)
	//}}AFX_EVENTSINK_MAP
END_EVENTSINK_MAP()

void CTripodDlg::OnPortalNotificationProcessedview(long lMsg, long lParam1, long lParam2, long lParam3) 
{
	// TODO: Add your control notification handler code here
	
	// This function is called at the camera's frame rate
    
#define NOTIFICATIONMSG_VIDEOHOOK	10

	// Declare some useful variables
	// QCSDKMFC.pdf (Quickcam MFC documentation) p. 103 explains the variables lParam1, lParam2, lParam3 too 
	
	LPBITMAPINFOHEADER lpBitmapInfoHeader; // Frame's info header contains info like width and height
	LPBYTE lpBitmapPixelData; // This pointer-to-long will point to the start of the frame's pixel data
    unsigned long lTimeStamp; // Time when frame was grabbed

	switch(lMsg) {
		case NOTIFICATIONMSG_VIDEOHOOK:
			{
				lpBitmapInfoHeader = (LPBITMAPINFOHEADER) lParam1; 
				lpBitmapPixelData = (LPBYTE) lParam2;
				lTimeStamp = (unsigned long) lParam3;

				grayScaleTheFrameData(lpBitmapInfoHeader, lpBitmapPixelData);
				doMyImageProcessing(lpBitmapInfoHeader); // Place where you'd add your image processing code
				displayMyResults(lpBitmapInfoHeader);

			}
			break;

		default:
			break;
	}	
}

void CTripodDlg::allocateDib(CSize sz)
{
	// Purpose: allocate information for a device independent bitmap (DIB)
	// Called from OnInitVideo

	if(m_destinationBitmapInfoHeader) {
		free(m_destinationBitmapInfoHeader);
		m_destinationBitmapInfoHeader = NULL;
	}

	if(sz.cx | sz.cy) {
		m_destinationBitmapInfoHeader = (LPBITMAPINFOHEADER)malloc(DibSize(sz.cx, sz.cy, 24));
		ASSERT(m_destinationBitmapInfoHeader);
		m_destinationBitmapInfoHeader->biSize = sizeof(BITMAPINFOHEADER);
		m_destinationBitmapInfoHeader->biWidth = sz.cx;
		m_destinationBitmapInfoHeader->biHeight = sz.cy;
		m_destinationBitmapInfoHeader->biPlanes = 1;
		m_destinationBitmapInfoHeader->biBitCount = 24;
		m_destinationBitmapInfoHeader->biCompression = 0;
		m_destinationBitmapInfoHeader->biSizeImage = DibImageSize(sz.cx, sz.cy, 24);
		m_destinationBitmapInfoHeader->biXPelsPerMeter = 0;
		m_destinationBitmapInfoHeader->biYPelsPerMeter = 0;
		m_destinationBitmapInfoHeader->biClrImportant = 0;
		m_destinationBitmapInfoHeader->biClrUsed = 0;
	}
}

void CTripodDlg::displayMyResults(LPBITMAPINFOHEADER lpThisBitmapInfoHeader)
{
	// displayMyResults: Displays results of doMyImageProcessing() in the videoport
	// Notes: StretchDIBits stretches a device-independent bitmap to the appropriate size

	CDC				*pDC;	// Device context to display bitmap data
	
	pDC = GetDC();	
	int nOldMode = SetStretchBltMode(pDC->GetSafeHdc(),COLORONCOLOR);

	StretchDIBits( 
		pDC->GetSafeHdc(),
		m_rectForProcessedView.left,				// videoportal left-most coordinate
		m_rectForProcessedView.top,					// videoportal top-most coordinate
		m_rectForProcessedView.Width(),				// videoportal width
		m_rectForProcessedView.Height(),			// videoportal height
		0,											// Row position to display bitmap in videoportal
		0,											// Col position to display bitmap in videoportal
		lpThisBitmapInfoHeader->biWidth,			// m_destinationBmp's number of columns
		lpThisBitmapInfoHeader->biHeight,			// m_destinationBmp's number of rows
		m_destinationBmp,							// The bitmap to display; use the one resulting from doMyImageProcessing
		(BITMAPINFO*)m_destinationBitmapInfoHeader, // The bitmap's header info e.g. width, height, number of bits etc
		DIB_RGB_COLORS,								// Use default 24-bit color table
		SRCCOPY										// Just display
	);
 
	SetStretchBltMode(pDC->GetSafeHdc(),nOldMode);

	ReleaseDC(pDC);

	// Note: 04/24/02 - Added the following:
	// Christopher Wagner cwagner@fas.harvard.edu noticed that memory wasn't being freed

	// Recall OnPortalNotificationProcessedview, which gets called everytime
	// a frame of data arrives, performs 3 steps:
	// (1) grayScaleTheFrameData - which mallocs m_destinationBmp
	// (2) doMyImageProcesing
	// (3) displayMyResults - which we're in now
	// Since we're finished with the memory we malloc'ed for m_destinationBmp
	// we should free it: 
	
	free(m_destinationBmp);

	// End of adds
}

void CTripodDlg::grayScaleTheFrameData(LPBITMAPINFOHEADER lpThisBitmapInfoHeader, LPBYTE lpThisBitmapPixelData)
{

	// grayScaleTheFrameData: Called by CTripodDlg::OnPortalNotificationBinaryview
	// Task: Read current frame pixel data and computes a grayscale version

	unsigned int	W, H;			  // Width and Height of current frame [pixels]
	BYTE            *sourceBmp;		  // Pointer to current frame of data
	unsigned int    row, col;
	unsigned long   i;
	BYTE			grayValue;

	BYTE			redValue;
	BYTE			greenValue;
	BYTE			blueValue;

    W = lpThisBitmapInfoHeader->biWidth;  // biWidth: number of columns
    H = lpThisBitmapInfoHeader->biHeight; // biHeight: number of rows

	// Store pixel data in row-column vector format
	// Recall that each pixel requires 3 bytes (red, blue and green bytes)
	// m_destinationBmp is a protected member and declared in binarizeDlg.h

	m_destinationBmp = (BYTE*)malloc(H*3*W*sizeof(BYTE));

	// Point to the current frame's pixel data
	sourceBmp = lpThisBitmapPixelData;

	for (row = 0; row < H; row++) {
		for (col = 0; col < W; col++) {

			// Recall each pixel is composed of 3 bytes
			i = (unsigned long)(row*3*W + 3*col);
        
			// The source pixel has a blue, green andred value:
			blueValue  = *(sourceBmp + i);
			greenValue = *(sourceBmp + i + 1);
			redValue   = *(sourceBmp + i + 2);

			// A standard equation for computing a grayscale value based on RGB values
			grayValue = (BYTE)(0.299*redValue + 0.587*greenValue + 0.114*blueValue);

			// The destination BMP will be a grayscale version of the source BMP
			*(m_destinationBmp + i)     = grayValue;
			*(m_destinationBmp + i + 1) = grayValue;
			*(m_destinationBmp + i + 2) = grayValue;
			
		}
	}
}


void CTripodDlg::doMyImageProcessing(LPBITMAPINFOHEADER lpThisBitmapInfoHeader)
{
	// doMyImageProcessing:  This is where you'd write your own image processing code
	// Task: Read a pixel's grayscale value and process accordingly

	unsigned int	W, H;			// Width and Height of current frame [pixels]
	unsigned int    row, col;		// Pixel's row and col positions
	unsigned long   i;				// Dummy variable for row-column vector
	int	    upperThreshold = 60;	// Gradient strength nessicary to start edge
	int		lowerThreshold = 30;	// Minimum gradient strength to continue edge
	unsigned long iOffset;			// Variable to offset row-column vector during sobel mask
	int rowOffset;					// Row offset from the current pixel
	int colOffset;					// Col offset from the current pixel
	int rowTotal = 0;				// Row position of offset pixel
	int colTotal = 0;				// Col position of offset pixel
	int Gx;							// Sum of Sobel mask products values in the x direction
	int Gy;							// Sum of Sobel mask products values in the y direction
	float thisAngle;				// Gradient direction based on Gx and Gy
	int newAngle;					// Approximation of the gradient direction
	bool edgeEnd;					// Stores whether or not the edge is at the edge of the possible image
	int GxMask[3][3];				// Sobel mask in the x direction
	int GyMask[3][3];				// Sobel mask in the y direction
	int newPixel;					// Sum pixel values for gaussian
	int gaussianMask[5][5];			// Gaussian mask

	W = lpThisBitmapInfoHeader->biWidth;  // biWidth: number of columns
    H = lpThisBitmapInfoHeader->biHeight; // biHeight: number of rows
	
	for (row = 0; row < H; row++) {
		for (col = 0; col < W; col++) {
			edgeDir[row][col] = 0;
		}
	}

	/* Declare Sobel masks */
	GxMask[0][0] = -1; GxMask[0][1] = 0; GxMask[0][2] = 1;
	GxMask[1][0] = -2; GxMask[1][1] = 0; GxMask[1][2] = 2;
	GxMask[2][0] = -1; GxMask[2][1] = 0; GxMask[2][2] = 1;
	
	GyMask[0][0] =  1; GyMask[0][1] =  2; GyMask[0][2] =  1;
	GyMask[1][0] =  0; GyMask[1][1] =  0; GyMask[1][2] =  0;
	GyMask[2][0] = -1; GyMask[2][1] = -2; GyMask[2][2] = -1;

	/* Declare Gaussian mask */
	gaussianMask[0][0] = 2;		gaussianMask[0][1] = 4;		gaussianMask[0][2] = 5;		gaussianMask[0][3] = 4;		gaussianMask[0][4] = 2;	
	gaussianMask[1][0] = 4;		gaussianMask[1][1] = 9;		gaussianMask[1][2] = 12;	gaussianMask[1][3] = 9;		gaussianMask[1][4] = 4;	
	gaussianMask[2][0] = 5;		gaussianMask[2][1] = 12;	gaussianMask[2][2] = 15;	gaussianMask[2][3] = 12;	gaussianMask[2][4] = 2;	
	gaussianMask[3][0] = 4;		gaussianMask[3][1] = 9;		gaussianMask[3][2] = 12;	gaussianMask[3][3] = 9;		gaussianMask[3][4] = 4;	
	gaussianMask[4][0] = 2;		gaussianMask[4][1] = 4;		gaussianMask[4][2] = 5;		gaussianMask[4][3] = 4;		gaussianMask[4][4] = 2;	
	

	/* Gaussian Blur */
	for (row = 2; row < H-2; row++) {
		for (col = 2; col < W-2; col++) {
			newPixel = 0;
			for (rowOffset=-2; rowOffset<=2; rowOffset++) {
				for (colOffset=-2; colOffset<=2; colOffset++) {
					rowTotal = row + rowOffset;
					colTotal = col + colOffset;
					iOffset = (unsigned long)(rowTotal*3*W + colTotal*3);
					newPixel += (*(m_destinationBmp + iOffset)) * gaussianMask[2 + rowOffset][2 + colOffset];
				}
			}
			i = (unsigned long)(row*3*W + col*3);
			*(m_destinationBmp + i) = newPixel / 159;
		}
	}

	/* Determine edge directions and gradient strengths */
	for (row = 1; row < H-1; row++) {
		for (col = 1; col < W-1; col++) {
			i = (unsigned long)(row*3*W + 3*col);
			Gx = 0;
			Gy = 0;
			/* Calculate the sum of the Sobel mask times the nine surrounding pixels in the x and y direction */
			for (rowOffset=-1; rowOffset<=1; rowOffset++) {
				for (colOffset=-1; colOffset<=1; colOffset++) {
					rowTotal = row + rowOffset;
					colTotal = col + colOffset;
					iOffset = (unsigned long)(rowTotal*3*W + colTotal*3);
					Gx = Gx + (*(m_destinationBmp + iOffset) * GxMask[rowOffset + 1][colOffset + 1]);
					Gy = Gy + (*(m_destinationBmp + iOffset) * GyMask[rowOffset + 1][colOffset + 1]);
				}
			}

			gradient[row][col] = sqrt(pow(Gx,2.0) + pow(Gy,2.0));	// Calculate gradient strength			
			thisAngle = (atan2(Gx,Gy)/3.14159) * 180.0;		// Calculate actual direction of edge
			
			/* Convert actual edge direction to approximate value */
			if ( ( (thisAngle < 22.5) && (thisAngle > -22.5) ) || (thisAngle > 157.5) || (thisAngle < -157.5) )
				newAngle = 0;
			if ( ( (thisAngle > 22.5) && (thisAngle < 67.5) ) || ( (thisAngle < -112.5) && (thisAngle > -157.5) ) )
				newAngle = 45;
			if ( ( (thisAngle > 67.5) && (thisAngle < 112.5) ) || ( (thisAngle < -67.5) && (thisAngle > -112.5) ) )
				newAngle = 90;
			if ( ( (thisAngle > 112.5) && (thisAngle < 157.5) ) || ( (thisAngle < -22.5) && (thisAngle > -67.5) ) )
				newAngle = 135;
				
			edgeDir[row][col] = newAngle;		// Store the approximate edge direction of each pixel in one array
		}
	}

	/* Trace along all the edges in the image */
	for (row = 1; row < H - 1; row++) {
		for (col = 1; col < W - 1; col++) {
			edgeEnd = false;
			if (gradient[row][col] > upperThreshold) {		// Check to see if current pixel has a high enough gradient strength to be part of an edge
				/* Switch based on current pixel's edge direction */
				switch (edgeDir[row][col]){		
					case 0:
						findEdge(0, 1, row, col, 0, lowerThreshold);
						break;
					case 45:
						findEdge(1, 1, row, col, 45, lowerThreshold);
						break;
					case 90:
						findEdge(1, 0, row, col, 90, lowerThreshold);
						break;
					case 135:
						findEdge(1, -1, row, col, 135, lowerThreshold);
						break;
					default :
						i = (unsigned long)(row*3*W + 3*col);
						*(m_destinationBmp + i) = 
						*(m_destinationBmp + i + 1) = 
						*(m_destinationBmp + i + 2) = 0;
						break;
					}
				}
			else {
				i = (unsigned long)(row*3*W + 3*col);
					*(m_destinationBmp + i) = 
					*(m_destinationBmp + i + 1) = 
					*(m_destinationBmp + i + 2) = 0;
			}	
		}
	}
	
	/* Suppress any pixels not changed by the edge tracing */
	for (row = 0; row < H; row++) {
		for (col = 0; col < W; col++) {	
			// Recall each pixel is composed of 3 bytes
			i = (unsigned long)(row*3*W + 3*col);
			// If a pixel's grayValue is not black or white make it black
			if( ((*(m_destinationBmp + i) != 255) && (*(m_destinationBmp + i) != 0)) || ((*(m_destinationBmp + i + 1) != 255) && (*(m_destinationBmp + i + 1) != 0)) || ((*(m_destinationBmp + i + 2) != 255) && (*(m_destinationBmp + i + 2) != 0)) ) 
				*(m_destinationBmp + i) = 
				*(m_destinationBmp + i + 1) = 
				*(m_destinationBmp + i + 2) = 0; // Make pixel black
		}
	}

	/* Non-maximum Suppression */
	for (row = 1; row < H - 1; row++) {
		for (col = 1; col < W - 1; col++) {
			i = (unsigned long)(row*3*W + 3*col);
			if (*(m_destinationBmp + i) == 255) {		// Check to see if current pixel is an edge
				/* Switch based on current pixel's edge direction */
				switch (edgeDir[row][col]) {		
					case 0:
						suppressNonMax( 1, 0, row, col, 0, lowerThreshold);
						break;
					case 45:
						suppressNonMax( 1, -1, row, col, 45, lowerThreshold);
						break;
					case 90:
						suppressNonMax( 0, 1, row, col, 90, lowerThreshold);
						break;
					case 135:
						suppressNonMax( 1, 1, row, col, 135, lowerThreshold);
						break;
					default :
						break;
				}
			}	
		}
	}
	
}

void CTripodDlg::findEdge(int rowShift, int colShift, int row, int col, int dir, int lowerThreshold)
{
	int W = 320;
	int H = 240;
	int newRow;
	int newCol;
	unsigned long i;
	bool edgeEnd = false;

	/* Find the row and column values for the next possible pixel on the edge */
	if (colShift < 0) {
		if (col > 0)
			newCol = col + colShift;
		else
			edgeEnd = true;
	} else if (col < W - 1) {
		newCol = col + colShift;
	} else
		edgeEnd = true;		// If the next pixel would be off image, don't do the while loop
	if (rowShift < 0) {
		if (row > 0)
			newRow = row + rowShift;
		else
			edgeEnd = true;
	} else if (row < H - 1) {
		newRow = row + rowShift;
	} else
		edgeEnd = true;	
		
	/* Determine edge directions and gradient strengths */
	while ( (edgeDir[newRow][newCol]==dir) && !edgeEnd && (gradient[newRow][newCol] > lowerThreshold) ) {
		/* Set the new pixel as white to show it is an edge */
		i = (unsigned long)(newRow*3*W + 3*newCol);
		*(m_destinationBmp + i) =
		*(m_destinationBmp + i + 1) =
		*(m_destinationBmp + i + 2) = 255;
		if (colShift < 0) {
			if (newCol > 0)
				newCol = newCol + colShift;
			else
				edgeEnd = true;	
		} else if (newCol < W - 1) {
			newCol = newCol + colShift;
		} else
			edgeEnd = true;	
		if (rowShift < 0) {
			if (newRow > 0)
				newRow = newRow + rowShift;
			else
				edgeEnd = true;
		} else if (newRow < H - 1) {
			newRow = newRow + rowShift;
		} else
			edgeEnd = true;	
	}	
}

void CTripodDlg::suppressNonMax(int rowShift, int colShift, int row, int col, int dir, int lowerThreshold)
{
	int W = 320;
	int H = 240;
	int newRow = 0;
	int newCol = 0;
	unsigned long i;
	bool edgeEnd = false;
	float nonMax[320][3];			// Temporarily stores gradients and positions of pixels in parallel edges
	int pixelCount = 0;					// Stores the number of pixels in parallel edges
	int count;						// A for loop counter
	int max[3];						// Maximum point in a wide edge
	
	if (colShift < 0) {
		if (col > 0)
			newCol = col + colShift;
		else
			edgeEnd = true;
	} else if (col < W - 1) {
		newCol = col + colShift;
	} else
		edgeEnd = true;		// If the next pixel would be off image, don't do the while loop
	if (rowShift < 0) {
		if (row > 0)
			newRow = row + rowShift;
		else
			edgeEnd = true;
	} else if (row < H - 1) {
		newRow = row + rowShift;
	} else
		edgeEnd = true;	
	i = (unsigned long)(newRow*3*W + 3*newCol);
	/* Find non-maximum parallel edges tracing up */
	while ((edgeDir[newRow][newCol] == dir) && !edgeEnd && (*(m_destinationBmp + i) == 255)) {
		if (colShift < 0) {
			if (newCol > 0)
				newCol = newCol + colShift;
			else
				edgeEnd = true;	
		} else if (newCol < W - 1) {
			newCol = newCol + colShift;
		} else
			edgeEnd = true;	
		if (rowShift < 0) {
			if (newRow > 0)
				newRow = newRow + rowShift;
			else
				edgeEnd = true;
		} else if (newRow < H - 1) {
			newRow = newRow + rowShift;
		} else
			edgeEnd = true;	
		nonMax[pixelCount][0] = newRow;
		nonMax[pixelCount][1] = newCol;
		nonMax[pixelCount][2] = gradient[newRow][newCol];
		pixelCount++;
		i = (unsigned long)(newRow*3*W + 3*newCol);
	}

	/* Find non-maximum parallel edges tracing down */
	edgeEnd = false;
	colShift *= -1;
	rowShift *= -1;
	if (colShift < 0) {
		if (col > 0)
			newCol = col + colShift;
		else
			edgeEnd = true;
	} else if (col < W - 1) {
		newCol = col + colShift;
	} else
		edgeEnd = true;	
	if (rowShift < 0) {
		if (row > 0)
			newRow = row + rowShift;
		else
			edgeEnd = true;
	} else if (row < H - 1) {
		newRow = row + rowShift;
	} else
		edgeEnd = true;	
	i = (unsigned long)(newRow*3*W + 3*newCol);
	while ((edgeDir[newRow][newCol] == dir) && !edgeEnd && (*(m_destinationBmp + i) == 255)) {
		if (colShift < 0) {
			if (newCol > 0)
				newCol = newCol + colShift;
			else
				edgeEnd = true;	
		} else if (newCol < W - 1) {
			newCol = newCol + colShift;
		} else
			edgeEnd = true;	
		if (rowShift < 0) {
			if (newRow > 0)
				newRow = newRow + rowShift;
			else
				edgeEnd = true;
		} else if (newRow < H - 1) {
			newRow = newRow + rowShift;
		} else
			edgeEnd = true;	
		nonMax[pixelCount][0] = newRow;
		nonMax[pixelCount][1] = newCol;
		nonMax[pixelCount][2] = gradient[newRow][newCol];
		pixelCount++;
		i = (unsigned long)(newRow*3*W + 3*newCol);
	}

	/* Suppress non-maximum edges */
	max[0] = 0;
	max[1] = 0;
	max[2] = 0;
	for (count = 0; count < pixelCount; count++) {
		if (nonMax[count][2] > max[2]) {
			max[0] = nonMax[count][0];
			max[1] = nonMax[count][1];
			max[2] = nonMax[count][2];
		}
	}
	for (count = 0; count < pixelCount; count++) {
		i = (unsigned long)(nonMax[count][0]*3*W + 3*nonMax[count][1]);
		*(m_destinationBmp + i) = 
		*(m_destinationBmp + i + 1) = 
		*(m_destinationBmp + i + 2) = 0;
	}
}

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