Image Processing Toolbox

bwfill

Fill background regions in a binary image

Note    This function is obsolete and may be removed in future versions. Use imfill instead.

Syntax

• BW2 = bwfill(BW1,c,r,n)
  BW2 = bwfill(BW1,n)
  [BW2,idx] = bwfill(...)
  
  BW2 = bwfill(x,y,BW1,xi,yi,n)
  [x,y,BW2,idx,xi,yi] = bwfill(...)
  
  BW2 = bwfill(BW1,'holes',n)
  [BW2,idx] = bwfill(BW1,'holes',n)
  

Description

BW2 = bwfill(BW1,c,r,n) performs a flood-fill operation on the input binary image BW1, starting from the pixel (r,c). If r and c are equal-length vectors, the fill is performed in parallel from the starting pixels (r(k),c(k)). n can have a value of either 4 or 8 (the default), where 4 specifies 4-connected foreground and 8 specifies 8-connected foreground. The foreground of BW1 comprises the on pixels (i.e., having value of 1).

BW2 = bwfill(BW1,n) displays the image BW1 on the screen and lets you select the starting points using the mouse. If you omit BW1, bwfill operates on the image in the current axes. Use normal button clicks to add points. Press
Backspace or Delete to remove the previously selected point. A shift-click, right-click, or double-click selects a final point and then starts the fill; pressing Return finishes the selection without adding a point.

[BW2,idx] = bwfill(...) returns the linear indices of all pixels filled by bwfill.

BW2 = bwfill(x,y,BW1,xi,yi,n) uses the vectors x and y to establish a nondefault spatial coordinate system for BW1. xi and yi are scalars or equal-length vectors that specify locations in this coordinate system.

[x,y,BW2,idx,xi,yi] = bwfill(...) returns the XData and YData in x and y; the output image in BW2; linear indices of all filled pixels in idx; and the fill starting points in xi and yi.

BW2 = bwfill(BW1,'holes',n) fills the holes in the binary image BW1. bwfill automatically determines which pixels are in object holes, and then changes the value of those pixels from 0 to 1. n defaults to 8 if you omit the argument.

[BW2,idx] = bwfill(BW1,'holes',n) returns the linear indices of all pixels filled in by bwfill.

If bwfill is used with no output arguments, the resulting image is displayed in a new figure.

Remarks

bwfill differs from many other binary image operations in that it operates on background pixels, rather than foreground pixels. If the foreground is 8-connected, the background is 4-connected, and vice versa. Note, however, that you specify the connectedness of the foreground when you call bwfill.

Class Support

The input image, BW1, must be a numeric or logical matrix. The output image, BW2, is logical.

Example

• BW1 = [1     0     0     0     0     0     0     0
         1     1     1     1     1     0     0     0
         1     0     0     0     1     0     1     0
         1     0     0     0     1     1     1     0
         1     1     1     1     0     1     1     1
         1     0     0     1     1     0     1     0
         1     0     0     0     1     0     1     0
         1     0     0     0     1     1     1     0]
  BW2 = bwfill(BW1,3,3,8)
  BW2 =
       1     0     0     0     0     0     0     0
       1     1     1     1     1     0     0     0
       1     1     1     1     1     0     1     0
       1     1     1     1     1     1     1     0
       1     1     1     1     0     1     1     1
       1     0     0     1     1     0     1     0
       1     0     0     0     1     0     1     0
       1     0     0     0     1     1     1     0
  I = imread('blood1.tif');
  BW3 = ~im2bw(I);
  BW4 = bwfill(BW3,'holes');
  imshow(BW3)
  figure, imshow(BW4)
  
  
  

See Also

bwselect, roifill

bweuler

bwhitmiss