How can I form a perimeter of variable thickness

I have a bw image with the largest area of a mouse cell. how can i get a perimeter with a variable thickness so that i can get a ring like border and i can manipulate the thickness as per wish. i have used bwperim but it only gives a very thin outline. What i want is that but thick and also i want to control the thickness. Thanks

Answer 1

[Image Analyst]

Call imdilate() on the image you get from bwperim().

[Scrat]

i wanted that when i specify a point at a distance from the perimeter towards centroid or specify a point at a distance from centroid towards the perimeter it will give a thick like border upto that point from the perimeter around the whole cell area. can imdilate do that? if so then which filter should i use and how?

[Image Analyst]

You can use impoint() or ginput() to specify the point. Then compute the distance from that point to all of the other points on the perimeter. Find the shortest distance - that will be the radius of the structuring element you use in imdilate(BW, se). Then mask the resulting dilated image with the original binary image that you passed in to bwperim

dilatedImage = imdilate(binaryImage, se);
finalImage = dilatedImage & binaryImage;

[Scrat]

I have applied imdilate() with a disk filter of radius 5 so that a ring of 5pixel thick forms. But the problem is it increases on both side of the perimeter. What I wanted is to increase the perimeter only towards the centroid so that i can measure the cell density in different edge thickness of the cell area. How can I achieve that?

[Image Analyst]

Did you read my prior comment? I told you how to do that. Another way is to simply call imerode() on the original binary image - the one you used when you called bwperim(). Just eat away the outer layers 2 or 5 pixels.

[Scrat]

Thanks a lot...that is exactly what i was looking for!!