 |
Course CVCis: Computer Vision with C#
Chapter C3: The Complete Code of the Polygon Project
Copyright © by V. Miszalok, last update: 2011-09-13
|
Main Menu after start of VC# 2010 Express: File -> New Project... -> Visual Studio installed templates: Windows Forms Application
Name: polygon1 -> Location: C:\temp -> Create directory for solution: switch off -> OK
Delete two superfluous files: Form1.Designer.cs and Program.cs.
Replace the preprogrammed code of Form1.cs by:
using System;
using System.Drawing;
using System.Windows.Forms;
using System.Collections;
public class Form1 : Form
{ [STAThread] static void Main() { Application.Run( new Form1() ); }
const Int32 xSize = 16;
const Int32 ySize = 16;
Byte[,] i0 = new Byte[ySize ,xSize];
Brush[] brush = new Brush[10];
Brush blackbrush = SystemBrushes.ControlText;
Brush redbrush = new SolidBrush( Color.Red );
Brush bluebrush = new SolidBrush( Color.Blue );
Pen redpen1 = new Pen( Color.Red, 1 );
Pen redpen5 = new Pen( Color.Red, 5 );
Pen whitepen;
Font arial10 = new Font("Arial",10);
Int32 i, j, x, y, dx, dy;
Byte threshold = 1;
Button[] button = new Button[ySize];
TextBox textboxEpsilon;
Point p0, p1, p2;
struct chaincode { public Point start; public String cracks; }
chaincode cc;
Graphics g;
ArrayList pointArray = new ArrayList();
ArrayList poly1 = new ArrayList();
ArrayList poly2 = new ArrayList();
public Form1()
{ BackColor = Color.White;
Text = "Polygon";
SetStyle( ControlStyles.ResizeRedraw, true );
Width = 800;
Height = 600;
for ( i=0; i < 10; i++ )
brush[i] = new SolidBrush( Color.FromArgb( i*25, i*25, i*25 ) );
for ( y=0; y < ySize; y++ )
{ button[y] = new Button();
Controls.Add( button[y] );
button[y].BackColor = Color.Gray;
button[y].Text = "nothing";
button[y].Name = y.ToString();
button[y].Click += new EventHandler( do_it );
}
button[0].Name = button[0].Text = "Polygon";
button[1].Name = button[1].Text = "eps=0";
button[2].Name = button[2].Text = "eps=sqrt(2)/2";
button[3].Name = button[3].Text = "eps=1";
button[4].Name = button[4].Text = "eps=sqrt(2)";
button[5].Name = button[5].Text = "eps>=2";
button[6].Name = button[6].Text = "Clear";
button[7].Name = "Threshold";
button[8].Name = button[8].Text = "Noise";
button[7].Text = String.Format("Threshold={0:#}",threshold);
textboxEpsilon = new TextBox(); Controls.Add(textboxEpsilon);
textboxEpsilon.Text = "2";
cc.cracks = "";
}
protected override void OnPaint( PaintEventArgs e )
{ g = e.Graphics;
String s;
Rectangle r = ClientRectangle;
dx = r.Width / ( xSize + 2 );
dy = ( r.Height - FontHeight - 1 ) / ySize;
for ( y=0; y < ySize; y++ )
{ button[y].Top = y*dy+1;
button[y].Left = xSize*dx+1;
if ( y != 5 ) button[y].Width = r.Width - button[y].Left - 2;
else button[y].Width = r.Width - button[y].Left - 25;
button[y].Height = dy - 2;
}
textboxEpsilon.Top = button[5].Top + ( button[5].Height - textboxEpsilon.Height ) / 2;
textboxEpsilon.Left = button[1].Left + button[5].Width + 1;
textboxEpsilon.Width = button[0].Width - button[5].Width - 2;
textboxEpsilon.TextAlign = HorizontalAlignment.Center;
for ( y=0; y < ySize; y++ )
for ( x=0; x < xSize; x++ )
g.FillRectangle( brush[i0[y,x]], x*dx, y*dy, dx, dy );
for ( x=0; x < xSize; x++ ) g.DrawLine( redpen1, x*dx, 0, x*dx, ySize*dy );
for ( y=0; y < ySize; y++ ) g.DrawLine( redpen1, 0, y*dy, xSize*dx, y*dy );
if ( poly1.Count == 0 )
{ s = "Draw something -> Polygon -> eps -> Clear -> Next";
g.DrawString( s, arial10, redbrush, (xSize*dx)/4, 0 );
return;
}
for ( i = 0; i < poly2.Count-1; i++ )
{ p0 = (Point)poly2[i];
p1 = (Point)poly2[i+1];
g.DrawLine(redpen5, p0.X*dx, p0.Y*dy, p1.X*dx, p1.Y*dy );
g.FillRectangle( bluebrush, p0.X*dx-5, p0.Y*dy-5, 11, 11 );
}
s = "No of vertices of the closed polygon = ";
if ( poly2.Count > 0 ) s = s + poly2.Count.ToString();
else if ( poly1.Count > 0 ) s = s + poly1.Count.ToString();
else s = "";
g.DrawString( s, arial10, redbrush, 0, ySize*dy );
}
protected override void OnMouseDown( MouseEventArgs e )
{ p0.X = e.X;
p0.Y = e.Y;
pointArray.Add( p0 );
whitepen = new Pen( Color.White, dx < dy ? dx : dy );
whitepen.StartCap = whitepen.EndCap = System.Drawing.Drawing2D.LineCap.Round;
}
protected override void OnMouseMove( MouseEventArgs e )
{ if ( e.Button == MouseButtons.None ) return;
p1.X = e.X;
p1.Y = e.Y;
//Insert an additional point if the distance is too far
if ( Math.Abs(p1.X - p0.X) >= dx || Math.Abs(p1.Y - p0.Y) >= dy )
pointArray.Add( new Point((p1.X + p0.X)/2, (p1.Y + p0.Y)/2) );
pointArray.Add( p1 );
g = this.CreateGraphics();
g.DrawLine( whitepen, p0, p1 );
p0 = p1;
}
protected void do_it( object sender, System.EventArgs e )
{ switch( ( (Button)sender).Name )
{ case "Threshold"://*************************************
if ( ++threshold > 9 ) threshold = 1;
button[7].Text = "Threshold=" + threshold.ToString();
cc.cracks =""; poly2.Clear(); break;
case "Noise"://****************************************
Random random = new Random();
for ( y=0; y < ySize; y++ )
for ( x=0; x < xSize; x++ )
{ Int32 noise = random.Next() % 3 - 1;//gives -1 or 0 or +1
noise += i0[y,x];//add former gray value
if ( noise < 0 ) i0[y,x] = 0;
else if ( noise > 9 ) i0[y,x] = 9;
else i0[y,x] = (Byte)noise;
}
cc.cracks =""; poly2.Clear(); break;
case "Clear"://*******************************************
for ( y=0; y < ySize; y++ )
for ( x=0; x < xSize; x++ ) i0[y,x] = 0;
threshold = 1; button[7].Text = "Threshold=1";
cc.cracks =""; pointArray.Clear(); poly1.Clear(); poly2.Clear(); break;
case "Polygon"://***********************************
//Digitize****************************************
for ( i = 0; i < pointArray.Count; i++ )
{ Point vertex = (Point)pointArray[i];
x = vertex.X / dx;
y = vertex.Y / dy;
try { if ( i0[y,x] < 9 ) i0[y,x]++; } catch{};
}
//Chain Code 8************************************
//Search for a vertical start crack
Byte leftpix;
for ( y=0; y < ySize; y++ )
for ( x=0; x < xSize; x++ )
{ if ( x > 0 ) leftpix = i0[y,x-1]; else leftpix = 0;
if ( leftpix < threshold && i0[y,x] >= threshold )
{ cc.start.X = x; cc.start.Y = y; goto start_crack_found; }
}
return; //nothing to start with
start_crack_found: poly1.Clear();
p0 = cc.start; poly1.Add(p0);
y++; p0.Y++; poly1.Add(p0);
System.Text.StringBuilder cracks = new System.Text.StringBuilder();
Char last_crack = 's';
do
{ switch ( last_crack )
{ case 'e': if ( x == xSize ) goto n;
if ( y < ySize && i0[y ,x ] >= threshold) goto s;
if ( i0[y-1,x ] >= threshold) goto e; goto n;
case 's': if ( y == ySize ) goto e;
if ( x > 0 && i0[y ,x-1] >= threshold) goto w;
if ( i0[y ,x ] >= threshold) goto s; goto e;
case 'w': if ( x == 0 ) goto s;
if ( y > 0 && i0[y-1,x-1] >= threshold) goto n;
if ( i0[y ,x-1] >= threshold) goto w; goto s;
case 'n': if ( y == 0 ) goto w;
if ( x < xSize && i0[y-1,x ] >= threshold) goto e;
if ( i0[y-1,x-1] >= threshold) goto n; goto w;
}
e: last_crack = 'e'; x++; p0.X++; poly1.Add( p0 ); continue;
s: last_crack = 's'; y++; p0.Y++; poly1.Add( p0 ); continue;
w: last_crack = 'w'; x--; p0.X--; poly1.Add( p0 ); continue;
n: last_crack = 'n'; y--; p0.Y--; poly1.Add( p0 ); continue;
} while ( x != cc.start.X || y != cc.start.Y ); //end of do
poly2 = (ArrayList)poly1.Clone();
break;
case "eps=0"://***********************************
polygon_remove_colinear_vertices( poly1, poly2 );
break;
case "eps=sqrt(2)/2"://***********************************
polygon_approximation( poly1, poly2, 0.5*Math.Sqrt( 2.0 ) );
break;
case "eps=1"://***********************************
polygon_approximation( poly1, poly2, 1.0f );
break;
case "eps=sqrt(2)"://***********************************
polygon_approximation( poly1, poly2, Math.Sqrt( 2.0 ) );
break;
case "eps>=2"://***********************************
double epsilon;
try { epsilon = Convert.ToSingle( textboxEpsilon.Text ); } catch { break; }
polygon_approximation( poly1, poly2, epsilon );
break;
}
Invalidate();
}
void polygon_approximation( ArrayList poly_in, ArrayList poly_out, double epsilon )
{ Int32 F, start=0, stop, dx, dy;
double length_line_p0p1, distance_of_p2_to_line_p0p1;
ArrayList poly_help = new ArrayList();
poly_help.Add( (Point)poly_in[0] );
for ( stop = start + 2; stop < poly_in.Count; stop++ )
{ p0 = (Point)poly_in[start];
p1 = (Point)poly_in[stop ];
dx = p1.X - p0.X;
dy = p1.Y - p0.Y;
length_line_p0p1 = Math.Sqrt( dx*dx + dy*dy );
for ( i = start + 1; i < stop; i++ )
{ p2 = (Point)poly_in[i];
F = ( p1.X - p0.X ) * ( p1.Y + p0.Y );//2 * area of trapezoid with p0-p1
F += ( p2.X - p1.X ) * ( p2.Y + p1.Y );//2 * area of trapezoid with p1-p2
F += ( p0.X - p2.X ) * ( p0.Y + p2.Y );//2 * area of trapezoid with p2-p0
//F is now 2 * the area of the triangle, can be negative
F = Math.Abs( F ); //area of a rectangle with length p0-p1
//next line computes the height of the rectangle
//this height is also the height of the triangle
distance_of_p2_to_line_p0p1 = (double)F / length_line_p0p1;
if ( distance_of_p2_to_line_p0p1 > epsilon )
{ start = stop - 1;
poly_help.Add( (Point)poly_in[start] );
break;
}
}
}
poly_help.Add( (Point)poly_in[0] );
if ( poly_help.Count > 3 ) polygon_remove_colinear_vertices( poly_help, poly_out );
else polygon_reduce_to_a_line( poly_in, poly_out );
}
void polygon_remove_colinear_vertices( ArrayList poly_in, ArrayList poly_out )
{ poly_out.Clear();
poly_out.Add((Point)poly_in[0]);
Int32 dx01, dy01, dx12, dy12, dx02, dy02;
double d01, d12, d02;
for ( i=0; i < poly_in.Count-2; i++ )
{ p0 = (Point)poly_in[i ];
p1 = (Point)poly_in[i+1];
p2 = (Point)poly_in[i+2];
dx01 = p1.X - p0.X; dy01 = p1.Y - p0.Y; d01 = Math.Sqrt( dx01*dx01 + dy01*dy01 );
dx12 = p2.X - p1.X; dy12 = p2.Y - p1.Y; d12 = Math.Sqrt( dx12*dx12 + dy12*dy12 );
dx02 = p2.X - p0.X; dy02 = p2.Y - p0.Y; d02 = Math.Sqrt( dx02*dx02 + dy02*dy02 );
if ( d01 + d12 > d02 ) poly_out.Add(p1);
}
poly_out.Add((Point)poly_in[0]);
}
void polygon_reduce_to_a_line( ArrayList poly_in, ArrayList poly_out )
{ int imax=1, distance, maxdistance=0;
p0 = (Point)poly_in[0];
for ( i=1; i < poly_in.Count; i++ )
{ p1 = (Point)poly_in[i];
dx = p1.X - p0.X; dy = p1.Y - p0.Y;
distance = dx*dx + dy*dy;
if ( distance > maxdistance ) { maxdistance = distance; imax = i; }
}
poly_out.Clear();
poly_out.Add( (Point)poly_in[ 0] );
poly_out.Add( (Point)poly_in[imax] );
poly_out.Add( (Point)poly_in[ 0] );
}
}
 |