This example shows how to use texture segmentation to identify regions based on their texture. Your goal is to segment two kinds of fabric in an image using texture filters.
I = imread('bag.png'); figure, imshow(I);
entropyfilt to create a texture image. The function
entropyfilt returns an array where each output pixel contains the entropy value of the 9-by-9 neighborhood around the corresponding pixel in the input image
I. Entropy is a statistical measure of randomness.
E = entropyfilt(I);
mat2gray to rescale the texture image
E so that its values are in the default range for a double image.
Eim = mat2gray(E); imshow(Eim);
Threshold the rescaled image
Eim to segment the textures. A threshold value of 0.8 is selected because it is roughly the intensity value of pixels along the boundary between the textures.
BW1 = imbinarize(Eim, .8);
imshow(BW1); figure, imshow(I);
The segmented objects in the binary image
BW1 are white. If you compare
I, you notice the top texture is overly segmented (multiple white objects) and the bottom texture is segmented almost in its entirety. You can extract the bottom texture using
BWao = bwareaopen(BW1,2000); imshow(BWao);
imclose to smooth the edges and to close any open holes in the object in
BWao. A 9-by-9 neighborhood is selected because this neighborhood was also used by
nhood = true(9); closeBWao = imclose(BWao,nhood); imshow(closeBWao)
imfill to fill holes in the object in
roughMask = imfill(closeBWao,'holes');
Compare the binary image
roughMask to the original image
I. Notice the mask for the bottom texture is not perfect because the mask does not extend to the bottom of the image. However, you can use
roughMask to segment the top texture.
imshow(roughMask); figure, imshow(I);
Get raw image of the top texture using
I2 = I; I2(roughMask) = 0; imshow(I2);
entropyfilt to calculate the texture image.
E2 = entropyfilt(I2); E2im = mat2gray(E2); imshow(E2im);
E2im using a global threshold.
BW2 = imbinarize(E2im);
imshow(BW2) figure, imshow(I);
If you compare
I, you notice there are two objects segmented in
bwareaopen to get a mask for the top texture.
mask2 = bwareaopen(BW2,1000); imshow(mask2);
mask2 to extract the top and bottom texture from
texture1 = I; texture1(~mask2) = 0; texture2 = I; texture2(mask2) = 0;
imshow(texture1); figure, imshow(texture2);
Outline the boundary between the two textures.
boundary = bwperim(mask2); segmentResults = I; segmentResults(boundary) = 255; imshow(segmentResults);
entropyfilt, you can use
rangefilt with other morphological functions to achieve similar segmentation results.
S = stdfilt(I,nhood); imshow(mat2gray(S));
R = rangefilt(I,ones(5)); imshow(R);