roifilt2

Filter region of interest (ROI) in image

Syntax

J = roifilt2(h,I,BW)

J = roifilt2(I,BW,fun)

Description

J = roifilt2(h,I,BW) filters regions of interest (ROIs) in the 2-D image I using the 2-D linear filter h. BW is a binary mask, the same size as I, that defines the ROIs in I. roifilt2 returns an image that consists of filtered values for pixels in locations where BW contains 1s, and unfiltered values for pixels in locations where BW contains 0s.

J = roifilt2(I,BW,fun) processes the data in ROIs of I using the function fun. The value fun must be a function handle.

Examples

Filter Image Using Polygonal Mask

Read an image into the workspace.

I = imread('eight.tif');

Define the vertices of the mask polygon.

c = [222 272 300 270 221 194];
r = [21 21 75 121 121 75];

Create the binary mask image.

BW = roipoly(I,c,r);

Filter the region of the image I specified by the mask BW.

H = fspecial('unsharp');
J = roifilt2(H,I,BW);

Display the original image and the filtered image.

imshow(I)

figure
imshow(J)

Input Arguments

h — Linear filter

2-D numeric matrix

Linear filter, specified as a 2-D numeric matrix.

Data Types: double

I — Image

2-D numeric matrix

Image, specified as a 2-D numeric matrix.

• If you specify a filter, h, then I can be any of the listed data types.

• If you specify a function handle, fun, then I can be any class supported by fun.

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

BW — Mask

2-D logical matrix | 2-D numeric matrix

Mask, specified as a 2-D logical matrix or a 2-D numeric matrix, the same size as I, containing 0s and 1s.

Data Types: logical

fun — Function handle

handle

Function handle, specified as a handle. For more information about function handles, see Create Function Handle.

Output Arguments

J — Filtered image

2-D matrix

Filtered image, returned as a 2-D matrix.

• If you specify a filter, h, then J has the same class as the input image, I.

• If you specify a function handle, fun, then the class of J is determined by fun.

Algorithms

If you specify a filter, h, then roifilt2 calls imfilter to implement the filter.

Version History

Introduced before R2006a