CODEWITHSUNDEEP
java
Joel
Joel

Reputation: 6107

Loop inside oval in Java

I need to examine each pixel inside an oval with Java. For drawing, I am currently using:

drawOval(x,y,r*2,R*2).

However, since I need to get each pixel inside the Oval, I would like to create a loop that iterates inside it (assuming I have x,y,r and R). Is there any built in functionality for this purpose?

Thanks,

Joel

Upvotes: 1

Views: 1049

Answers (3)

trashgod
trashgod

Reputation: 205785

Java's Ellipse2D implements the Shape interface, so you can use one of the latter's contains() methods as required. It's also possible to render the Shape into a BufferedImage and traverse its WritableRaster.

Upvotes: 2

darioo
darioo

Reputation: 47183

I don't think there's any built in functionality for this.

Let's go through this step by step.

Assuming that your ellipse's center is at (0,0), one radius is a, other is b, the canonical equation is 

x^2/a^2+y^2/b^2=1

Multiplying both sides with a^2 and b^2, you get

x^2*b^2+y^2*a^2=a^2*b^2

Now, you must do a double for loop. a and b must be positive. Pseudocode:

for x = -a; x <= a; ++x:
   for y = -b; y <= b; ++y:
      if(x^2*b^2+y^2*a^2 <= a^2*b^2)
         // you're in your ellipse, do as you please

Of course, this will work only if center is at (0,0), so if you want this algorithm to work, shift your points appropriately using translation. If you leave the center somewhere else, this algorithm will get messier.

Note: didn't test this. If somebody sees a mistake, please point it out.

Upvotes: 1

Stan Kurilin
Stan Kurilin

Reputation: 15792

simple canonical implicit equation for Oval is (with center 0; 0)

alt text

So yo can iterate throw all possible coordinates and check it using this equation.

Upvotes: 1

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