cc2bw

Convert connected components to binary image

Since R2024a

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Syntax

BW = cc2bw(CC)

BW = cc2bw(CC,ObjectsToKeep=objectsToKeep)

Description

BW = cc2bw(CC) creates a binary image from the connected components (objects) in CC.

example

BW = cc2bw(CC,ObjectsToKeep=objectsToKeep) creates a binary image from a subset of connected components, specified by objectsToKeep.

example

Examples

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Filter on Multiple Image Properties

Open Live Script

Read and display an image.

I = imread("blobs.png");
imshow(I)

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

Create a connected components structure.

CC = bwconncomp(I);

Filter the structure and keep round objects. Display the filtered image.

CC = bwpropfilt(CC,"Circularity",[0.7 1]);
imshow(cc2bw(CC))

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

Filter the structure again and keep large objects. Display the filtered image.

CC = bwpropfilt(CC,"Area",[20 Inf]);
imshow(cc2bw(CC))

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

Create Binary Image with Subset of Filtered Objects

Open Live Script

Read a binary image and detect the connected components.

BW = imread("text.png");
CC = bwconncomp(BW);

Measure the area of each connected component and return the results as a table.

p = regionprops("table",CC,"Area");

Create a binary image that contains only the 2nd through 10th largest connected components. Display the result.

[~,idx] = sort(p.Area,"descend");
BWfilt = cc2bw(CC,ObjectsToKeep=idx(2:10));
imshow(BWfilt)

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

Isolate Vertically Oriented Regions

Open Live Script

Read a grayscale image of grains of rice, then convert the image to binary.

I = imread("rice.png");
BW = imbinarize(I);
imshow(BW)

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

Measure the area and bounding box of each region.

CC = bwconncomp(BW); 
stats = regionprops("table",CC,"Area","BoundingBox");

Select regions for whom these conditions apply:

The area is greater than 50 pixels
The bounding box is less than 15 pixels wide and is greater than or equal to 20 pixels tall.

area = stats.Area;
bbox = stats.BoundingBox;
selection = (area > 50) & (bbox(:,3) < 15) & (bbox(:,4) >= 20);
BW2 = cc2bw(CC,ObjectsToKeep=selection);

Display the filtered image.

imshow(BW2)

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

Input Arguments

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`CC` — Connected components
structure

Connected components (objects), specified as a structure with four fields.

Field	Description
`Connectivity`	Connectivity of the connected components
`ImageSize`	Size of the binary image
`NumObjects`	Number of connected components in the binary image.
`PixelIdxList`	1-by-`NumObjects` cell array where the k-th element in the cell array is a vector containing the linear indices of the pixels in the k-th object.

`objectsToKeep` — Objects to keep
positive integer | vector of positive integers | logical vector

Objects to keep, specified as one of these values.

Positive integer or vector of positive integers — Keep the object or objects whose index is included in objectsToKeep. The length of objectsToKeep is less than or equal to CC.NumObjects.
Logical vector — Keep the objects whose corresponding element in objectsToKeep is true. The length of objectsToKeep must be equal to CC.NumObjects.

Output Arguments

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`BW` — Binary image
logical array

Binary image, returned as a logical array of the same size as CC.ImageSize.

Data Types: logical

Extended Capabilities

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

Usage notes and limitations:

cc2bw supports the generation of C and C++ code (requires MATLAB^® Coder™). For more information, see Code Generation for Image Processing.
If you generate code for the cc2bw function directly, then CC.PixelIdxList must be homogeneous. This code shows how to make CC.PixelIdxList homogeneous by using the makeHomogeneous (MATLAB Coder) function.
```
CC = bwconncomp(BW);
CC2 = bwpropfilt(CC,"Area",10);
typeCC = coder.typeof(CC2);
typeCC.Fields.PixelIdxList = makeHomogeneous(typeCC.Fields.PixelIdxList);

codegen cc2bw -args {typeCC}
```
If you generate code for a wrapper function, then you do not need to make CC.PixelIdxList homogeneous. For example, this command generates code for a wrapper function named myFunction.
```
codegen myFunction -args {BW}
```
Here is a sample definition for the wrapper function myFunction that includes a call to the cc2bw function.
```
function out = myFunction(BW) %#codegen
    CC = bwconncomp(BW);
    CC2 = bwpropfilt(CC,"Area",10);
    out = cc2bw(CC2);
end
```

Version History

Introduced in R2024a

expand all

R2024a: Generate C code using MATLAB Coder

cc2bw now supports the generation of C code (requires MATLAB Coder).

cc2bw

Syntax

Description

Examples

Filter on Multiple Image Properties

Create Binary Image with Subset of Filtered Objects

Isolate Vertically Oriented Regions

Input Arguments

CC — Connected components structure

objectsToKeep — Objects to keep positive integer | vector of positive integers | logical vector

Output Arguments

BW — Binary image logical array

Extended Capabilities

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

Version History

R2024a: Generate C code using MATLAB Coder

See Also

`CC` — Connected components
structure

`objectsToKeep` — Objects to keep
positive integer | vector of positive integers | logical vector

`BW` — Binary image
logical array

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