In other words, it replaces the interior color of the object with the fill color. Instead of relying on the boundary of the object, it relies on the fill color. We can paint such objects with a specified interior color instead of searching for particular boundary color as in boundary filling algorithm. Sometimes we come across an object where we want to fill the area and its boundary with different colors. Step 4 − Fill all those pair of coordinates that are inside polygons and ignore the alternate pairs. Step 3 − Sort the intersection point in the increasing order of X coordinate i.e. As per the figure shown above, they are named as p0, p1, p2, p3. Name each intersection point of the polygon. Step 2 − ScanLine intersects with each edge of the polygon from Ymin to Ymax.
Step 1 − Find out the Ymin and Ymax from the given polygon. The following steps depict how this algorithm works.
This algorithm works by intersecting scanline with polygon edges and fills the polygon between pairs of intersections. In this chapter, we will see how we can fill polygons using different techniques.
For filling polygons with particular colors, you need to determine the pixels falling on the border of the polygon and those which fall inside the polygon. Polygon is an ordered list of vertices as shown in the following figure.
