imfill

Fill image regions and holes

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Syntax

BW2 = imfill(BW,locations)

BW2 = imfill(BW,locations,conn)

BW2 = imfill(BW,"holes")

BW2 = imfill(BW,conn,"holes")

I2 = imfill(I)

I2 = imfill(I,conn)

BW2 = imfill(BW)

BW2 = imfill(BW,0,conn)

[BW2, locations_out] = imfill(BW)

Description

BW2 = imfill(BW,locations) performs a flood-fill operation on background pixels of the input binary image BW, starting from the points specified in locations.

example

BW2 = imfill(BW,locations,conn) fills the area defined by locations, where conn specifies the connectivity.

BW2 = imfill(BW,"holes") fills holes in the input binary image BW. In this syntax, a hole is a set of background pixels that cannot be reached by filling in the background from the edge of the image.

example

BW2 = imfill(BW,conn,"holes") fills holes in the binary image BW, where conn specifies the connectivity.

example

I2 = imfill(I) fills holes in the grayscale image I. In this syntax, a hole is defined as an area of dark pixels surrounded by lighter pixels.

example

I2 = imfill(I,conn) fills holes in the grayscale image I, where conn specifies the connectivity.

example

BW2 = imfill(BW) displays the binary image BW on the screen and lets you define the region to fill by selecting points interactively with the mouse. To use this syntax, BW must be a 2-D image.

Press Backspace or Delete to remove the previously selected point. Shift-click, right-click, or double-click to select a final point and start the fill operation. Press Return to finish the selection without adding a point.

BW2 = imfill(BW,0,conn) lets you override the default connectivity as you interactively specify locations.

[BW2, locations_out] = imfill(BW) returns the locations of points selected interactively in locations_out. To use this syntax, BW must be a 2-D image.

Examples

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Fill Image from Specified Starting Point

Open Live Script

BW1 = logical([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 = imfill(BW1,[3 3],8)

BW2 = 8x8 logical array

   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   1   1   1   1
   1   0   0   1   1   1   1   0
   1   0   0   0   1   1   1   0
   1   0   0   0   1   1   1   0

Fill Holes in a Binary Image

Open Live Script

Read image into workspace.

I = imread('coins.png');
figure
imshow(I)
title('Original Image')

Figure contains an axes object. The hidden axes object with title Original Image contains an object of type image.

Convert image to binary image.

BW = imbinarize(I);
figure
imshow(BW)
title('Original Image Converted to Binary Image')

Figure contains an axes object. The hidden axes object with title Original Image Converted to Binary Image contains an object of type image.

Fill holes in the binary image and display the result.

BW2 = imfill(BW,'holes');
figure
imshow(BW2)
title('Filled Image')

Figure contains an axes object. The hidden axes object with title Filled Image contains an object of type image.

Fill Holes in a Grayscale Image

Open Live Script

I = imread('tire.tif');
I2 = imfill(I);
figure, imshow(I), figure, imshow(I2)

Figure contains an axes object. The hidden axes object contains an object of type image.

Input Arguments

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`BW` — Binary image
logical array

Binary image, specified as a logical array of any dimension.

Example: BW = imread('text.png');

Data Types: logical

`locations` — Linear indices identifying pixel locations
numeric vector of positive integers | 2-D numeric matrix of positive integers

Linear indices identifying pixel locations, specified as a numeric vector or 2-D numeric matrix of positive integers. If locations is a p-by-1 vector, then it contains the linear indices of the starting locations. If locations is a p-by-ndims(BW) matrix, then each row contains the array indices of one of the starting locations.

Example: [3 3]

Data Types: double

`I` — Grayscale image
numeric array

Grayscale image, specified as a numeric array of any dimension.

Example: I = imread('cameraman.tif');

`conn` — Pixel connectivity
`4` | `8` | `6` | `18` | `26` | 3-by-3-by- ... -by-3 matrix of `0`s and `1`s

Pixel connectivity, specified as one of the values in this table. The default connectivity is 4 for 2-D images, and 6 for 3-D images.

Value	Meaning
Two-Dimensional Connectivities
`4`	Pixels are connected if their edges touch. The neighborhood of a pixel are the adjacent pixels in the horizontal or vertical direction.	Current pixel is shown in gray.
`8`	Pixels are connected if their edges or corners touch. The neighborhood of a pixel are the adjacent pixels in the horizontal, vertical, or diagonal direction.	Current pixel is shown in gray.
Three-Dimensional Connectivities
`6`	Pixels are connected if their faces touch. The neighborhood of a pixel are the adjacent pixels in: One of these directions: in, out, left, right, up, and down	Current pixel is shown in gray.
`18`	Pixels are connected if their faces or edges touch. The neighborhood of a pixel are the adjacent pixels in: One of these directions: in, out, left, right, up, and down A combination of two directions, such as right-down or in-up	Current pixel is center of cube.
`26`	Pixels are connected if their faces, edges, or corners touch. The neighborhood of a pixel are the adjacent pixels in: One of these directions: in, out, left, right, up, and down A combination of two directions, such as right-down or in-up A combination of three directions, such as in-right-up or in-left-down	Current pixel is center of cube.

For higher dimensions, imfill uses the default value conndef(ndims(BW),'minimal').

Connectivity can also be defined in a more general way for any dimension by specifying a 3-by-3-by- ... -by-3 matrix of 0s and 1s. The 1-valued elements define neighborhood locations relative to the center element of conn. Note that conn must be symmetric about its center element. See Specifying Custom Connectivities for more information.

Data Types: double | logical

Output Arguments

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`BW2` — Filled binary image
logical array

Filled binary image, returned as logical array.

`locations_out` — Linear indices of pixel locations
numeric vector | numeric matrix

Linear indices of pixel locations, returned as a numeric vector or matrix.

`I2` — Filled grayscale image
numeric array

Filled grayscale image, returned as a numeric array.

Algorithms

imfill uses an algorithm based on morphological reconstruction [1].

References

[1] Soille, P., Morphological Image Analysis: Principles and Applications, Springer-Verlag, 1999, pp. 173–174.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

imfill supports the generation of C code (requires MATLAB^® Coder™). Note that if you choose the generic MATLAB Host Computer target platform, imfill generates code that uses a precompiled, platform-specific shared library. Use of a shared library preserves performance optimizations but limits the target platforms for which code can be generated. For more information, see Types of Code Generation Support in Image Processing Toolbox.
The optional input arguments, conn and 'holes', must be compile-time constants.
Input argument 'holes' is not supported, if the input is a binary image.
imfill supports up to 3-D inputs only. (No N-D support.)
The interactive syntaxes to select points are not supported. For example, the syntax imfill(BW,0,CONN) is not supported.
With the locations input argument, once you select a format at compile time, you cannot change it at run time. However, the number of points in locations can be varied at run time.

Thread-Based Environment
Run code in the background using MATLAB® `backgroundPool` or accelerate code with Parallel Computing Toolbox™ `ThreadPool`.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Usage notes and limitations:

Inputs must be 2-D, supporting only the 2-D connectivities (4 and 8).
The interactive syntaxes to select points are not supported. For example, the syntax imfill(BW) is not supported.

For more information, see Image Processing on a GPU.

Version History

Introduced before R2006a

expand all

R2022b: Support for thread-based environments

imfill now supports thread-based environments.

imfill

Syntax

Description

Examples

Fill Image from Specified Starting Point

Fill Holes in a Binary Image

Fill Holes in a Grayscale Image

Input Arguments

BW — Binary image logical array

locations — Linear indices identifying pixel locations numeric vector of positive integers | 2-D numeric matrix of positive integers

I — Grayscale image numeric array

conn — Pixel connectivity 4 | 8 | 6 | 18 | 26 | 3-by-3-by- ... -by-3 matrix of 0s and 1s

Output Arguments

BW2 — Filled binary image logical array

locations_out — Linear indices of pixel locations numeric vector | numeric matrix

I2 — Filled grayscale image numeric array

Algorithms

References

Extended Capabilities

C/C++ Code Generation Generate C and C++ code using MATLAB® Coder™.

Thread-Based Environment Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

GPU Arrays Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Version History

R2022b: Support for thread-based environments

See Also

`BW` — Binary image
logical array

`locations` — Linear indices identifying pixel locations
numeric vector of positive integers | 2-D numeric matrix of positive integers

`I` — Grayscale image
numeric array

`conn` — Pixel connectivity
`4` | `8` | `6` | `18` | `26` | 3-by-3-by- ... -by-3 matrix of `0`s and `1`s

`BW2` — Filled binary image
logical array

`locations_out` — Linear indices of pixel locations
numeric vector | numeric matrix

`I2` — Filled grayscale image
numeric array

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Thread-Based Environment
Run code in the background using MATLAB® `backgroundPool` or accelerate code with Parallel Computing Toolbox™ `ThreadPool`.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.