$\Large \color{red}\Omega$ This tutorial will show you how to draw Circle Rectangle/Square Oval/Ellipse on top of photo in ObjectiveC/iOS

1. Write a minimum App
A. Create header file[*.h] AppDelegate : UIResponder<UIApplicaitonDelegate> 

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;

@end

B. In your implementation file, you only need to override one following method,
the method only set the background of window to while and makes the window visible

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    
    [self.window makeKeyAndVisible];
    
    // Override point for customization after application launch.
    return YES;
}

2. Draw label on your App, add the following code in previous method.
The code creates a label and add the label to subView of your UIApplication 

    
    // create simple text label
    UILabel *myLabel = [[UILabel alloc] initWithFrame:CGRectMake(50, 50, 300, 300)];
    [myLabel setTextColor:[UIColor redColor]];
    [myLabel setBackgroundColor:[UIColor clearColor]];
    [myLabel setFont:[UIFont fontWithName: @"Trebuchet MS" size: 20.0f]];
    [myLabel setText:@"Supper Simple Application"];
    
    [self.window addSubview:myLabel];

3. Load an image on your window.
A. Get an image and rename it to myimage.jpg
B. Drag the image to your Images.xcassets window (see screen shot)


C. Declare UIImageView* imageView on your header file[*.h]

D. Add the bellow code to following method

- (void)applicationDidFinishLaunching:(UIApplication *)application 

    self.imageView = [[UIImageView alloc]initWithFrame:self.window.bounds];
    self.imageView.image=[UIImage imageNamed:@"myimage.jpg"];
    [self.window addSubview:self.imageView];

3. Draw Circle, Oval/Ellipse and Rectangle/Square.

// draw circle
- (CAShapeLayer*)drawCircle:(CGPoint)location radius:(CGFloat)radius {
    CAShapeLayer* shapeLayer = [CAShapeLayer layer];

    UIBezierPath *path = [UIBezierPath bezierPath];
    [path addArcWithCenter:location
                    radius:radius
                startAngle:0.0
                  endAngle:M_PI * 2.0
                 clockwise:YES];
    
    shapeLayer.path = [path CGPath];
    shapeLayer.strokeColor = [[UIColor redColor] CGColor];
    shapeLayer.fillColor = nil;
    shapeLayer.lineWidth = 5.0;
    return shapeLayer;
}

// draw oval
-(CAShapeLayer*)drawOval:(CGPoint) location semimajor:(CGFloat)semimajor semiminor:(CGFloat) semiminor{
    CAShapeLayer* shapeLayer = [CAShapeLayer layer];
    
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:CGRectMake(location.x-semimajor, location.y-semiminor, 2*semimajor, 2*semiminor)];
    
    shapeLayer.path = [path CGPath];
    
    shapeLayer.strokeColor = [[UIColor greenColor] CGColor];
    shapeLayer.fillColor = [[UIColor blackColor] CGColor];
    shapeLayer.lineWidth = 1.0;
    return shapeLayer;
}

// draw rectangle
-(CAShapeLayer*)drawRectangle:(CGPoint) location semiWidth:(CGFloat) semiWidth semiHeight:(CGFloat)semiHeight{
    CAShapeLayer* shapeLayer = [CAShapeLayer layer];
    UIBezierPath* path = [UIBezierPath bezierPath];
    
    // start point
    [path moveToPoint:CGPointMake(location.x - semiWidth, location.y - semiHeight)];
    
    // draw lines
    [path addLineToPoint:CGPointMake(location.x + semiWidth, location.y - semiHeight)];
    [path addLineToPoint:CGPointMake(location.x + semiWidth, location.y + semiHeight)];
    [path addLineToPoint:CGPointMake(location.x - semiWidth, location.y + semiHeight)];
    [path addLineToPoint:CGPointMake(location.x - semiWidth, location.y - semiHeight)];
    //[path closePath];
    
    shapeLayer.path = [path CGPath];
    
    shapeLayer.strokeColor = [[UIColor yellowColor] CGColor];
    shapeLayer.fillColor = [[UIColor blackColor] CGColor];
    shapeLayer.lineWidth = 1.0;
    return shapeLayer;
}

4. Use above three methods and you can see the final output 

    CAShapeLayer* layerCircle = [self drawCircle:CGPointMake(100, 100) radius:60];
    [self.imageView.layer addSublayer:layerCircle];

    // draw oval
    CAShapeLayer* layerOval = [self drawOval:CGPointMake(200, 100) semimajor:40 semiminor:20];
    [self.imageView.layer addSublayer:layerOval];

    // draw rectangle
    CAShapeLayer* layerRect = [self drawRectangle:CGPointMake(200, 200) semiWidth:60 semiHeight:80];
    [self.imageView.layer addSublayer:layerRect];