how can i obtain the final result after roipoly?

hello

i have agrayscale image

i want to extract my target roi

so i wrote this

m=imread(.....); BW=roipoly(m);

after that how can i obtain the roi filling with grayscale ? i mean how can i make benefit of the polygon that i obtained in BW to get my roi as agrayscale?

thanks

Answer 1

[David Young]

If you want to fill the polygon with interpolated grayscale, have a look at roifill.

If you want to have an image that only shows the original grayscale within the polygon, you can use

mnew = m .* cast(BW, class(m));

EDIT Added in response to comment

If you wish to extract the part of the image containing the region, you can do it like this:

BWprops = regionprops(BW, 'BoundingBox');
smallim = imcrop(mnew, BWprops.BoundingBox);

You can then position smallim in the figure, or copy it into the centre of a larger array.

[mmm ssss]

thank you very much because this is very useful to me.

but how i centering the mnew image at the center of whole figure

[David Young]

See edit.

[mmm ssss]

i want to put the picture after

roipoly(m) ;

mnew = m .* cast(BW, class(m));

at the center of whole figure.

imcrope will take a part from image ,

iwant to put the whole image in the center of the figure.

[Image Analyst]

Do you mean that you want to paste of copy of the stuff inside the polygon over the top of the original image with the center of the extracted polygonal region now translated so that it lies at the center of your original image?

[mmm ssss]

i read that "we must calculate COG (center of Gravity) for my ROI and then translation of the grayscale region to the center of image after making background =zero"

this is my target in this question .

i wish that you can help me.

thanks

[David Young]

You can find the CoG of the ROI using the 'Centroid' option in regionprops. You could get both the bounding box and the centroid in the same call to regionprops.

You can copy the small region into the middle of a larger array by assigning it to a particular range of indices, as in

bigarray(rowstart:rowend, colstart:colend) = smallarray;

The problem is then working out values for rowstart etc., but you should find that reasonably straightforward.

Alternatively, you can use padarray to put a border of zeros round the small image.

[mmm ssss]

You can find the CoG of the ROI using the 'Centroid' option in regionprops. You could get both the bounding box and the centroid in the same call to regionprops.

this is done by :

bw = imread('text.png');

L = bwlabel(bw);

s = regionprops(L, 'centroid','Boundingbox');

now what do you mean by this:

You can copy the small region into the middle of a larger array by assigning it to a particular range of indices, as in

bigarray(rowstart:rowend, colstart:colend) = smallarray;

The problem is then working out values for rowstart etc., but you should find that reasonably straightforward.

Alternatively, you can use padarray to put a border of zeros round the small image.

in codes how this can be implemented?