iOS: draw a UIImage of circle at a UIView's center - ios

Question

I have a circle image with radius 50, and now I want to put the circyle's center the same as my View's center like this:
- (void)drawRect:(CGRect)rect {
UIImage *arrow = [UIImage imageWithPDFNamed:#"circle" atSize:CGSizeMake(50, 50)];
[arrow drawAtPoint:self.center];
}
But drawAtPoint is not drawing at the center.
I want to know how to locate the center of the image? so I can draw it?

Answer 1

From Apple's documentation for UIImage
This method draws the entire image in the current graphics context,
respecting the image’s orientation setting. In the default coordinate
system, images are situated down and to the right of the specified
point. This method respects any transforms applied to the current
graphics context, however.
So offset the center with half the image width and height to draw the center of the image on the center of your view.
- (void)drawRect:(CGRect)rect {
CGSize imageSize = CGSizeMake(50,50);
UIImage *arrow = [UIImage imageWithPDFNamed:#"circle" atSize:imageSize];
[arrow drawAtPoint:CGPointMake(self.center.x-imageSize.width/2., self.center.y-imageSize.height/2.)];
}

Answer 2

You don't need to draw it, just assign it's center to your view's center
arrowsuperview.center = self.center

Answer 3

Try this. This is how you find the center of a subview inside a view
childView.center = CGPointMake(parentView.bounds.size.width / 2, parentView.bounds.size.height / 2);

Answer 4

try this..
UIImageView *circleImageView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 50, 50)];
circleImageView.image = yourCircleImage;
circleImageView.center = self.view.center;
[circleImageView setContentMode:UIViewContentModeCenter];
[self.view addSubview:circleImageView];

Answer 5

Calculate the center of the UIView using following code and draw the image using the drawAtPoint function.
- (void)drawRect:(CGRect)rect
{
CGPoint ptCenter = {rect.size.width / 2.0f, rect.size.height / 2.0f};
[arrow drawAtPoint:ptCenter];
}
Another simple approach:
You can also achieve the result using storyboard/xib and Auto Layout. Instead of drawing the image in drawRect use an UIImageView to hold your image and position the imageview using Autolayout constraints.