Objective-C generating a random point which lies in given cgrect

Question

my requirement is generating a random point in a given area, i.e i have an Cg Rectangle of some space and I need to generate a random point in this rectangle ..

how can I proceed in this scenario?

Quxflux · Answer 1 · 2015-08-18T08:07:35.000

10

- (CGPoint)randomPointInRect:(CGRect)r
{
    CGPoint p = r.origin;

    p.x += arc4random_uniform((u_int32_t) CGRectGetWidth(r));
    p.y += arc4random_uniform((u_int32_t) CGRectGetHeight(r));

    return p;
}

edited Aug 18 '15 at 08:07

answered Nov 01 '13 at 10:57

Quxflux

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+ 1, but you should use [`arc4random_uniform(u_int32_t upper_bound)`](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/arc4random_uniform.3.html). Reason as per doc: `"arc4random_uniform() is recommended over constructions like ``arc4random() % upper_bound'' as it avoids "modulo bias" when the upper bound is not a power of two."` ;) – HAS Nov 01 '13 at 11:04

score 5 · Answer 2 · answered Jun 11 '16 at 06:07

The original question asks specifically for Objective-C, but a Swift solution might help someone.

extension CGRect {
    func randomPointInRect() -> CGPoint {
        let origin = self.origin
        return CGPointMake(CGFloat(arc4random_uniform(UInt32(self.width))) + origin.x, CGFloat(arc4random_uniform(UInt32(self.height))) + origin.y)
    }
}

score 0 · Answer 3 · edited May 23 '17 at 12:09

0

First, check out this post for generating random numbers: Generating random numbers in Objective-C

Then use CGPointMake(x,y) to create your point using random numbers:

int x = RandomNumberGenerator1Output;
int y = RandomNumberGenerator2Output;

CGPoint myPoint = CGpointMake(x, y);

edited May 23 '17 at 12:09

Community

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answered Nov 01 '13 at 05:34

Amos

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score 0 · Answer 4 · answered Nov 01 '13 at 05:38

Same as any random number generator. You need two random numbers, x and y. Just generate x between 0 and rect.size.width and y between 0 and rect.size.height

Add rect.origin.x or rect.origin.y respectively. Random number generation is well covered elsewhere. Look for the arc4random family of functions.

score 0 · Answer 5 · edited May 23 '17 at 12:09

To generate a random point in a rectangle to need to generate random X and Y between Start and End coordinates of your rectangle.

if RECT is your rectangle then -

X = Random (RECT-Origion-X,RECT-Size-Width)
Y = Random (RECT-Origion-y,RECT-Size-Height)

If you want to know how to generate a random number between two numbers then you can go here - Generate Random Numbers Between Two Numbers in Objective-C

Objective-C generating a random point which lies in given cgrect

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