Generate binary image of geometric shapes?

I need a code where I can generate different geometric shapes in a form of a binary image. Please assist me as I am not very good with Matlab Image Processing.

Answer 1

[Image Analyst]

I thought I helped you in your prior posting of this question. Here is the code from there:

http://www.mathworks.com/matlabcentral/answers/214028#comment_283303

xCenter = 12;
yCenter = 10;

% Modification to the FAQ is the next two lines.
numSides = 6; % <===  CHANGE THIS NUMBER
theta = linspace(0, 2*pi, numSides + 1);
% Rotate the shape by subtracting an offset.
theta = theta - pi/3;

radius = 5;
x = radius * cos(theta) + xCenter;
y = radius * sin(theta) + yCenter;
plot(x, y);
axis square;
xlim([0 20]);
ylim([0 20]);
grid on;

Feel free to adapt as necessary to change center, radius, rotation angle, etc.

You can make a binary image of it with poly2mask()

binaryImage = poly2mask(x, y, rows, columns);

You have to specify the number of rows and columns you want in the image.

[Yashlin Naidoo]

The problem I have is to change the radius to side lengths like width,height etc.An example for a rectangle,it has a width and height,I cant seem to figure out how to change the radius to side lengths to get the other shapes.

[Image Analyst]

Well, let's try to take this one simple step at a time. Let's say we have a square. 4 sides. Put a dot at the middle and draw lines out to the 4 vertices. Now, what is the angle from the center? It's 90 degrees, which is just 360/4. So now draw a line from the center to the middle of the side. What is the angle now? It's half that, or 360/(2*#sides). Let's call it theta. And from the middle of the side to the vertex is s/2 if s is full side length. So now we have sind(theta) = (s/2)/radius = s / (2*radius). Or radius = s / (2 * sind(theta)), where theta = 180/numSides. sind() is the version of sin() that works in degrees rather than radians. So plug in that equation to get the radius from the side length and you should have it.

Answer 2

[Alka Nair]

Hi, For generating geometric shapes in binary images use STREL to create the structuring element, for example, suppose you want to generate a square. The steps are as follows: >>img = zeros(100,100); >>imgLogical = logical(img); >>img(50,50)=1; % fixing the initial seed point >>se1 = strel('square',12); >>im2 = imdilate(f,se1);

Please refer to the documentation for STREL at the following location: http://www.mathworks.com/help/images/ref/strel.html

[Yashlin Naidoo]

I need to generate 8 distinct shapes from specified variables,hopefully I'll get to understand your method to generate these shapes:

1. Circle

2. Square

3. Triangle

4. Rectangle

5. Pentagon

6. Hexagon

7. Ellipse

8. Octagon