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Generate binary image of geometric shapes?

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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.

Accepted Answer

Image Analyst
Image Analyst on 6 May 2015
Edited: Image Analyst on 6 May 2015
I thought I helped you in your prior posting of this question. Here is the code from there:
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
Yashlin Naidoo on 6 May 2015
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
Image Analyst on 6 May 2015
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.

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More Answers (1)

Alka Nair
Alka Nair on 6 May 2015
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:
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Yashlin Naidoo
Yashlin Naidoo on 6 May 2015
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

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