Question

i’m writing a little coffeescript/js app that allows user to design icons ( 16×16 pixels or 32X32 pixels ).
The icon is actually a 2 dimensional array with color cells. A cell can have a color or be empty.

I want the user to be able to fill blank cells with a “bucket paint” tool.

It means that

• if the user clicks on a blank cell , all the cells that are blank next to the clicked cell with be filled with the choosen color , until it reaches a colored cell

• if the user clicks on a colored cell , all the cells that are next to the clicked cell and share the same color will be filled , but not the blank ones nor the colored ones ( with another color ).

The app already allows the user to fill cells one by one with a chosen color , or delete colored cells with a pen tool.

Any suggestions ?

(ps : i’m not using html canvas to draw )

Answer 1

Since this is only 16×16 or 32×32 you can use a recursive solution:

Say your starting point is to change pixel x/y from color A to color B (A or B can be empty).

In pseudo code:

function floodfill(x,y,A,B) {
  if ((x<0) || (x>15) || (y<0) || (y>15)) return;
  if (get_color(x,y)!=A) return;
  set_color(x,y,B);
  floodfill(x-1,y-1,A,B);
  floodfill(x-1,y,A,B);
  floodfill(x-1,y+1,A,B);
  floodfill(x,y-1,A,B);
  floodfill(x,y+1,A,B);
  floodfill(x+1,y-1,A,B);
  floodfill(x+1,y,A,B);
  floodfill(x+1,y+1,A,B);
}