grayconnected

Select contiguous image region with similar gray values

Syntax

BW = grayconnected(I,row,column)

BW = grayconnected(I,row,column,tolerance)

Description

BW = grayconnected(I,row,column) finds connected regions of similar intensity in the grayscale image I. You specify the intensity value to use as a starting point, the seed pixel, by row and column indices. By default, grayconnected includes connected pixels with values in the range [seedpixel–32,seedpixel+32] for integer-valued images and within the range [seedpixel-0.1,seedpixel+0.1] for floating point images. grayconnected returns a binary mask image, BW, where all of the foreground pixels are 8-connected to the seed pixel at (row, column) by pixels of similar intensity.

BW = grayconnected(I,row,column,tolerance) finds connected regions of similar intensity in a grayscale image, where tolerance specifies the range of intensity values to include in the mask, as in [(seedpixel-tolerance),(seedpixel+tolerance)].

Examples

Create Binary Mask from Connected Pixels

Create small sample image.

I = uint8([20 22 24 23 25 20 100
           21 10 12 13 12 30 6
           22 11 13 12 13 25 5
           23 13 13 13 13 20 5
           24 13 13 12 12 13 5
           25 26  5 28 29 50 6]);

Create mask image, specifying the seed location by row and column and the tolerance. Since the seed location specifies the pixel with the value 23 and the tolerance is 3 , the range of grayscale values is [20,26].

seedrow = 4

seedrow = 4

seedcol = 1

seedcol = 1

tol = 3 

tol = 3

BW = grayconnected(I,seedrow,seedcol,tol)

BW = 6x7 logical array

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

Input Arguments

I — Input grayscale image

real, nonsparse 2-D matrix

Input grayscale image, specified as a real, nonsparse, 2-D matrix.

Example: BW = grayconnected(I,50,40);

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

row — Row index of seed location

real, positive, scalar integer.

Row index of seed location, specified as a real, positive, scalar integer.

Example: BW = grayconnected(I,50,40);

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

column — Column index of seed location

real, positive, scalar integer

Column index of seed location, specified as a real, positive, scalar integer.

Example: BW = grayconnected(I,50,40);

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

tolerance — Range of intensity values to include in the mask

32 for integer valued images, 0.1 for floating point images (default) | numeric scalar

Range of intensity values to include in the mask, specified as a numeric scalar. The range is defined as [(seedvalue-tolerance),(seedvalue+tolerance)]. By default, grayconnected includes connected pixels with values in the range [seedpixel–32,seedpixel+32] for integer-valued images and within the range [seedpixel-0.1,seedpixel+0.1] for floating point images.

Example: BW = grayconnected(I,50,40,5);

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32

Output Arguments

BW — Mask binary image

logical array

Mask binary image, returned as a logical array where all of the foreground pixels are 8-connected to the seed pixel at (row,column) by pixels of similar intensity.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• grayconnected supports the generation of C code (requires MATLAB^® Coder™). Note that if you choose the generic MATLAB Host Computer target platform, grayconnected 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 Code Generation Using a Shared Library.