Implement polygon scanline renderer

src/sig/Edge.java

@@ -0,0 +1,33 @@
+package sig;
+
+public class Edge {
+	Point a,b;
+	int min_y;
+	int max_y;
+	int min_x;
+	int max_x;
+	double x_of_min_y;
+	double inverse_slope;
+	public Edge(Point a, Point b) {
+		super();
+		this.a = a;
+		this.b = b;
+		min_y=Math.min(a.y, b.y);
+		max_y=Math.max(a.y, b.y);
+		min_x=Math.min(a.x, b.x);
+		max_x=Math.max(a.x, b.x);
+		if (a.y==min_y) {
+			x_of_min_y=a.x;
+		} else {
+			x_of_min_y=b.x;
+		}
+		
+		inverse_slope=(double)(a.x-b.x)/(a.y-b.y);
+	}
+	@Override
+	public String toString() {
+		return "Edge [a=" + a + ", b=" + b + ", min_y=" + min_y + ", max_y=" + max_y + ", min_x=" + min_x + ", max_x="
+				+ max_x + ", x_of_min_y=" + x_of_min_y + ", inverse_slope=" + inverse_slope + "]";
+	}
+	
+}

src/sig/Panel.java

@@ -6,6 +6,8 @@ import java.awt.Image;
 import java.awt.Toolkit;
 import java.awt.image.ColorModel;
 import java.awt.image.MemoryImageSource;
+import java.util.ArrayList;
+import java.util.List;
 
 import javax.swing.JPanel;
 
@@ -17,6 +19,8 @@ public class Panel extends JPanel implements Runnable {
     private Image imageBuffer;   
     private MemoryImageSource mImageProducer;   
     private ColorModel cm;   
+    int scanLine=0;
+    int nextScanLine=0;
 
     public Panel() {
         super(true);
@@ -85,7 +89,101 @@ public class Panel extends JPanel implements Runnable {
         	}
         }
         
+        FillPolygon(new Point[] {
+        		new Point(135,2),
+        		new Point(166,96),
+        		new Point(265,97),
+        		new Point(185,156),
+        		new Point(215,251),
+        		new Point(134,192),
+        		new Point(54,251),
+        		new Point(84,156),
+        		new Point(4,97),
+        		new Point(103,96),
+        });
+    }
     
+    public void FillPolygon(Point...points) {
+    	Edge[] edges = new Edge[points.length];
+    	List<Edge> edges_sorted = new ArrayList<Edge>();
+    	for (int i=0;i<points.length;i++) {
+    		edges[i] = new Edge(points[i],points[(i+1)%points.length]);
+    		if (edges_sorted.size()==0) {
+    			edges_sorted.add(edges[i]);
+    		} else {
+    			boolean inserted=false;
+    			for (int j=0;j<edges_sorted.size();j++) {
+    				Edge e2 = edges_sorted.get(j);
+    				if (e2.min_y>edges[i].min_y) {
+    					edges_sorted.add(j,edges[i]);
+    					inserted=true;
+    					break;
+    				} else 
+    				if (e2.min_y==edges[i].min_y){
+    					if (e2.min_x>edges[i].min_x) {
+    						edges_sorted.add(j,edges[i]);
+    						inserted=true;
+    						break;
+    					}
+    				}
+    			}
+    			if (!inserted) {
+    				edges_sorted.add(edges[i]);
+    			}
+    		}
+    	}
+    	List<Edge> active_edges = new ArrayList<Edge>();
+    	scanLine = edges_sorted.get(0).min_y-1;
+    	nextScanLine = scanLine+1;
+    	do {
+    		if (active_edges.size()%2==0) {
+	    		for (int i=0;i<active_edges.size();i+=2) {
+	    			Edge e1 = active_edges.get(i);
+	    			Edge e2 = active_edges.get(i+1);
+	    			for (int x=(int)Math.round(e1.x_of_min_y);x<=e2.x_of_min_y;x++) {
+	    				pixel[scanLine*width+x]=(255<<16)+(0<<8)+0;
+	    			}
+	    		}
+	    		for (int i=0;i<active_edges.size();i++) {
+	    			Edge e = active_edges.get(i);
+	    			if (e.max_y==scanLine+1) {
+	    				active_edges.remove(i--);
+	    			} else {
+	    				e.x_of_min_y+=e.inverse_slope;
+	    			}
+	    		}
+	    		scanLine++;
+	    		GetNextScanLineEdges(edges_sorted, active_edges);
+    		}
+    	}
+    	while (active_edges.size()>0);
+    }
+
+	private void GetNextScanLineEdges(List<Edge> edges_sorted, List<Edge> active_edges) {
+		if (scanLine==nextScanLine) {
+	    	for (int i=0;i<edges_sorted.size();i++) {
+	    		Edge e = edges_sorted.get(i);
+	    		if (e.min_y==scanLine) {
+	    			e = edges_sorted.remove(i--);
+	    			boolean inserted=false;
+	    			for (int j=0;j<active_edges.size();j++) {
+	    				if (e.x_of_min_y<active_edges.get(j).x_of_min_y) {
+	    					active_edges.add(j,e);
+	    					inserted=true;
+	    					break;
+	    				}
+	    			}
+	    			if (!inserted) {
+	    				active_edges.add(e);
+	    			}
+	    			
+	    		} else
+	    		if (e.min_y>scanLine) {
+	    			nextScanLine=e.min_y;
+	    			break;
+	    		}
+	    	}
+    	}
 	}
 
 	@Override

src/sig/Point.java

@@ -0,0 +1,32 @@
+package sig;
+
+public class Point {
+	int x,y;
+
+	public Point(int x, int y) {
+		super();
+		this.x = x;
+		this.y = y;
+	}
+
+	public int getX() {
+		return x;
+	}
+
+	public void setX(int x) {
+		this.x = x;
+	}
+
+	public int getY() {
+		return y;
+	}
+
+	public void setY(int y) {
+		this.y = y;
+	}
+
+	@Override
+	public String toString() {
+		return "Point(" + x + "," + y + ")";
+	}
+}