Flood filling for number plate recognition

Question

I have a number plate which is a binary image.

I performed dilation to the image to thicken the edges then "flood filling", lastly erosion for thinning:

But i want my output to be like this:

Can anyone help me, please? And show me how to get the desired output.

ab=imread('test1.png');

level=graythresh(ab);
ab=im2bw(ab,level);

se=strel('disk',1);
ab=imdilate(ab,se); 


ab=imfill(ab,'holes');
ab=bwmorph(ab,'thin',1);
ab=imerode(ab,strel('line',3,90));

figure();imshow(ab,[]); title('floodFilling');

Answer 1

Text is just single layer fill so I do it in C++ like this:

int x,y,e;
int c0=0x00000000; // space color
int c1=0x00FFFFFF; // edge color
int co=0x00FF0000; // outside tmp color
int ci=0x000000FF; // inside tmp color
// grow/flood fill c0 neigbouring c1 with c2
#define fill(c0,c1,c2)\
for (e=1;e;)\
 for (e=0,y=1;y<pic1.ys-1;y++)\
  for (   x=1;x<pic1.xs-1;x++)\
   if (pic1.p[y][x].dd==c0)\
    if ((pic1.p[y-1][x].dd==c1)\
      ||(pic1.p[y+1][x].dd==c1)\
      ||(pic1.p[y][x-1].dd==c1)\
      ||(pic1.p[y][x+1].dd==c1)) { e=1; pic1.p[y][x].dd=c2; }
// copy data pic0 is source pic1 is output
pic1=pic0;
// 0. draw border rectangle for growth fill start with co
for (x=0        ,y=0;y<pic1.ys;y++) pic1.p[y][x].dd=co;
for (x=pic1.xs-1,y=0;y<pic1.ys;y++) pic1.p[y][x].dd=co;
for (x=0,y=0        ;x<pic1.xs;x++) pic1.p[y][x].dd=co;
for (x=0,y=pic1.ys-1;x<pic1.xs;x++) pic1.p[y][x].dd=co;
fill(c0,co,co); // 1. grow outer border
fill(c1,co,co); // 2. grow outer edges
fill(c0,co,ci); // 3. create outer fill edge
fill(c0,ci,ci); // 4. fill the inside
// 5. merge / recolor
for (y=0;y<pic1.ys;y++)
 for (x=0;x<pic1.xs;x++)
    {
    e=c0;
    if ((pic0.p[y][x].dd==c1)||(pic1.p[y][x].dd==ci)) e=c1;
    pic1.p[y][x].dd=e;
    }
#undef fill

Here are how the stages looks like:

• 

Algorithm is like this:

1. draw border rectangle for growth fill start with co (some unused color)
2. grow outer border to nearest text edges with co
3. fill outer edges (they disappear) with co
4. create outer fill edge with ci (some unused color)
5. fill the inside with ci

6. merge / recolor source and result images

   copy edges from source image and inside from result image the rest is space

I use my own picture class for images so some members are:

xs,ys size of image in pixels
p[y][x].dd is pixel at (x,y) position as 32 bit integer type
clear(color) - clears entire image
resize(xs,ys) - resizes image to new resolution

If you have special characters that have more layers

then just add more stages ... layer is how many layers of space there can be from most inner space/hole to the outer space also you can loop until no more layer found ...

Answer 2

let use this code it will use for you . thanks to @ spektre .

 ab=imread('test1.png');

level=graythresh(ab);
ab=im2bw(ab,level);

se=strel('disk',1);
ab=imdilate(ab,se);
figure();imshow(ab,[]); title('floodFilling');
ab1=imfill(ab,'holes');
ab1(ab==1)=0;
figure();imshow(ab1,[]); title('floodFilling');

Answer 3

You can do this with a few other clever calls to imfill. Here is a way, assuming your binary image is in the array BW:

Tmp = imfill(BW, 'holes');
Tmp2 = imfill(Tmp-BW, 'holes');
Res = Tmp - imfill(BW & Tmp2, 'holes');

and Res is a binary image that contains the desired output: