From d46a4ad83f0c6c10e39ec29790e42fc504e16887 Mon Sep 17 00:00:00 2001
From: Kshitij <kshitijk@tuta.io>
Date: Fri, 1 Dec 2023 19:27:17 +0530
Subject: [PATCH] Added scan line fill code

---
 README.md          |  19 +++---
 Scan Line Fill.cpp | 154 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 165 insertions(+), 8 deletions(-)
 create mode 100644 Scan Line Fill.cpp

diff --git a/README.md b/README.md
index fbd6deb..3529452 100644
--- a/README.md
+++ b/README.md
@@ -8,13 +8,6 @@ This repository contains codes, write-ups, lab manuals, lab notes and question p
 
 ### Codes
 
-#### Digital Differential Analyzer (DDA):
-> Digital Differential Analyzer (DDA) is a line-drawing algorithm for digital displays, using incremental calculations to plot points between endpoints.
-
-1. [Line](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/DDA-line.cpp)
-2. [Triangle](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/DDA-triangle.cpp)
-3. [Circle](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/DDA-circle.cpp)
-
 #### Lab Codes:
 1. [Assignment A-1 (Scan Fill)](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/Assignment%20A-1%20%28Scan%20Fill%29.cpp)
 2. Assignment A-2 (Cohen Sutherland Line Clipping)
@@ -28,6 +21,16 @@ This repository contains codes, write-ups, lab manuals, lab notes and question p
 8. [Assignment C-6c (Sunrise and Sunset)](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/Assignment%20C-6c%20%28Sunrise%20and%20Sunset%29.cpp)
 9. [Assignment C-7b (Bouncing Ball)](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/Assignment%20C-7b%20%28Bouncing%20Ball%29.cpp)
 
+#### Digital Differential Analyzer (DDA):
+> Digital Differential Analyzer (DDA) is a line-drawing algorithm for digital displays, using incremental calculations to plot points between endpoints.
+
+1. [Line](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/DDA-line.cpp)
+2. [Triangle](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/DDA-triangle.cpp)
+3. [Circle](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/DDA-circle.cpp)
+
+#### Miscellaneous Codes:
+- [Scan Line Fill](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/Scan%20Line%20Fill.cpp)
+
 ### Lab Manual
 - [Full lab manual](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/lab-manual/CGL%20Lab%20Manual.pdf)
 
@@ -46,7 +49,7 @@ This repository contains codes, write-ups, lab manuals, lab notes and question p
 1. [Unit 1 - Graphics Primitives and Scan Conversion Algorithms](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/notes/Unit%201)
 2. [Unit 2 - Polygon, Windowing and Clipping](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/notes/Unit%202)
 3. [Unit 3 - 2D, 3D Transformations and Projections](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/notes/Unit%203)
-4. [Unit 4 - Light, Colour, Shading and Hidden Surfaces](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/notes/Unit%204)
+4. [Unit 4 - Light, Colour, Shading and Hidden Surfaces](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/notes/Unit%204/)
 5. [Unit 5 - Curves and Fractals](https://git.kska.io/sppu-se-comp-codes/CG/src/branch/main/notes/Unit%205)
 
 #### Lab Notes (Computer Graphics **Lab**)
diff --git a/Scan Line Fill.cpp b/Scan Line Fill.cpp
new file mode 100644
index 0000000..ee97644
--- /dev/null
+++ b/Scan Line Fill.cpp	
@@ -0,0 +1,154 @@
+/* Define the structure to store the edges*/
+#include<iostream>
+#include<graphics.h>
+using namespace std;
+struct edge{
+	int x1,y1,x2,y2,flag;
+};
+int main()
+{
+	int gd=DETECT,gm,n,i,j,k;
+	struct edge ed[10],temped;
+	float dx,dy,m[10],x_int[10],inter_x[10];
+	int x[10],y[10],ymax=0,ymin=480,yy,temp;
+	initgraph(&gd,&gm,NULL);
+	
+/*read the number of vertices of the polygon*/
+	cout<<"Enter the no.of vertices of the graph :";
+	cin>>n;
+	
+/*read the vertices of the polygon and also find ymax and ymin*/
+	cout<<"Enter the vertices";
+	for(i=0;i<n;i++)
+	{
+		cin>>x[i];
+		cin>>y[i];
+		if(y[i]>ymax)
+			ymax=y[i];
+		if(y[i]<ymin)
+			ymin=y[i];
+		ed[i].x1=x[i];
+		ed[i].y1=y[i];
+	}
+	
+
+/*store the edge information*/
+	cout<<"\nEdge Information\n";
+	for(i=0;i<n-1;i++)
+	  {
+		ed[i].x2=ed[i+1].x1;
+		ed[i].y2=ed[i+1].y1;
+		ed[i].flag=0;
+          cout<<"("<<ed[i].x1<<", "<<ed[i].y1<<") ("<<ed[i].x2<<", "<<ed[i].y2<<")"<<endl;
+	  }
+          ed[i].x2=ed[0].x1;
+	     ed[i].y2=ed[0].y1;
+	     ed[i].flag=0;
+	     cout<<"("<<ed[i].x1<<", "<<ed[i].y1<<") ("<<ed[i].x2<<", "<<ed[i].y2<<")"<<endl;
+	
+
+/*Check for y1>y2, if not interchnge y1 and y2 */
+	cout<<"\nUpdated Edge Information\n";
+	for(i=0;i<n;i++)
+	{
+		if(ed[i].y1 < ed[i].y2)
+		{
+			temp=ed[i].x1;
+			ed[i].x1=ed[i].x2;
+			ed[i].x2=temp;
+			temp=ed[i].y1;
+			ed[i].y1=ed[i].y2;
+			ed[i].y2=temp;
+		}
+		cout<<"("<<ed[i].x1<<", "<<ed[i].y1<<") ("<<ed[i].x2<<", "<<ed[i].y2<<")"<<endl;
+	}
+	
+
+/*Draw the polygon*/
+	for(i=0;i<n;i++)
+	{
+		line(ed[i].x1, ed[i].y1,ed[i].x2,ed[i].y2);
+	}
+
+	
+/*calculating 1/slope of each edge*/
+	for(i=0;i<n;i++)
+	{
+		dx=ed[i].x2-ed[i].x1;
+		dy=ed[i].y2-ed[i].y1;
+		if(dy==0)
+		{
+			m[i]=0;
+		}
+		else
+		{
+			m[i]=dx/dy;
+		}
+		inter_x[i]=ed[i].x1;
+	}
+	
+	yy=ymax;
+
+	//Working with Active edges
+	while(yy>ymin)
+	{
+		//cout<<"\n\t"<<yy;
+		for(i=0;i<n;i++)
+		{
+			if(yy>ed[i].y2 && yy<=ed[i].y1)
+				ed[i].flag=1;               //Active edge
+			else
+				ed[i].flag=0;              //not Active edge
+		}
+		j=0;
+		for(i=0;i<n;i++)
+		{
+			if(ed[i].flag==1)
+			{
+				if(yy==ed[i].y1)
+				{
+					x_int[j]=ed[i].x1;
+					j++;
+                    }
+				else
+				{
+					x_int[j]=inter_x[i]+(-m[i]);
+					inter_x[i]=x_int[j];
+					j++;
+				}
+			}
+		}
+
+
+		/*sorting the x intersection*/
+		for(i=0;i<j;i++)
+		{
+			for(k=0;k<j-1;k++)
+			{
+				if(x_int[k]>x_int[k+1])
+				{
+					temp=(int)x_int[k];
+					x_int[k]=x_int[k+1];
+					x_int[k+1]=temp;
+				}
+			}
+		}
+
+
+		/*extracting pairs of values to draw lilnes*/
+		for(i=0;i<j;i=i+2)
+		{    setcolor(GREEN);
+			line((int)x_int[i],yy,(int)x_int[i+1],yy);
+		}
+		yy--;
+		delay(50);
+	}//while
+	delay(10000);
+	closegraph();
+}
+
+
+
+/*
+Enter the vertices 80 20 100 80 150 60 130 200 40 250
+*/