09. Filled Area Primitives - 2

Dated: 12-05-2025

Boundary Fill

We can find paint-scan function in common interactive paint packages.
Idea is to have a closed figure, then selecting a point within the figure with a color to fill.

The algorithm requires has parameters:

• Coordinates of starting point
• Fill color
• Color of boundary

Algorithm

• Check the pixel for boundary color
• Check the pixel for fill color
• Set the pixel in fill color
• Run the process for neighbors

Flood Fill

Sometimes, we may want to replace the color of all connected pixels.
For this case, we just need something like if(getPixel(x, y).color == oldColor).

Neighbors

Algorithm with 4 neighbors.

Algorithm with 8 neighbors