code

 

 

/*

 Erica Sadun, http://ericasadun.com

 iPhone Developer's Cookbook, 3.0 Edition

 BSD License, Use at your own risk

 */

 

#import <UIKit/UIKit.h>

 

#define COOKBOOK_PURPLE_COLOR  [UIColor colorWithRed:0.20392f green:0.19607f blue:0.61176f alpha:1.0f]

#define BARBUTTON(TITLE, SELECTOR)    [[[UIBarButtonItem alloc] initWithTitle:TITLE style:UIBarButtonItemStylePlain target:self action:SELECTOR] autorelease]

#define POINT(X)       [[self.points objectAtIndex:X] CGPointValue]

 

@interface TouchView : UIView

{

        NSMutableArray *points;

        CGRect circle;

}

@property (retain) NSMutableArray *points;

@end

 

@implementation TouchView

@synthesize points;

 

- (BOOL) isMultipleTouchEnabled {return NO;}

 

// Return dot product of two vectors normalized

float dotproduct (CGPoint v1, CGPoint v2)

{

        float dot = (v1.x * v2.x) + (v1.y * v2.y);

        float a = ABS(sqrt(v1.x * v1.x + v1.y * v1.y));

        float b = ABS(sqrt(v2.x * v2.x + v2.y * v2.y));

        dot /= (a * b);

 

        return dot;

}

 

// Return distance between two points

float distance (CGPoint p1, CGPoint p2)

{

        float dx = p2.x - p1.x;

        float dy = p2.y - p1.y;

 

        return sqrt(dx*dx + dy*dy);

}

 

// Calculate and return least bounding rectangle

- (CGRect) centeredRectangle

{

        float x = 0.0f;

        float y = 0.0f;

        for (NSValue *pt in self.points)

        {

               x += [pt CGPointValue].x;

               y += [pt CGPointValue].y;

        }

 

        // Calculate weighted center

        x /= self.points.count;

        y /= self.points.count;

 

        float minx = 9999.0f;

        float maxx = -9999.0f;

        float miny = 9999.0f;

        float maxy = -9999.0f;

 

        for (NSValue *pt in self.points)

        {

               minx = MIN(minx, [pt CGPointValue].x);

               miny = MIN(miny, [pt CGPointValue].y);

               maxx = MAX(maxx, [pt CGPointValue].x);

               maxy = MAX(maxy, [pt CGPointValue].y);

        }

 

        return CGRectMake(minx, miny, (maxx - minx), (maxy - miny));

}

 

// Return a point with respect to a given origin

CGPoint centerPoint(CGPoint pt, CGPoint origin)

{

        return CGPointMake(pt.x - origin.x, pt.y - origin.y);

}

 

// On new touch, start a new array of points

- (void) touchesBegan:(NSSet *) touches withEvent:(UIEvent *) event

{

        self.points = [NSMutableArray array];

        CGPoint pt = [[touches anyObject] locationInView:self];

        [self.points addObject:[NSValue valueWithCGPoint:pt]];

}

 

// Add each point to the array

- (void) touchesMoved:(NSSet *) touches withEvent:(UIEvent *) event

{

        CGPoint pt = [[touches anyObject] locationInView:self];

        [self.points addObject:[NSValue valueWithCGPoint:pt]];

        [self setNeedsDisplay];

}

 

// At the end of touches, determine whether a circle was drawn

- (void) touchesEnded:(NSSet *) touches withEvent:(UIEvent *) event

{

        if (!self.points) return;

        if (self.points.count < 3) return;

 

        // Test 1: The start and end points must be between 60 pixels of each other

        CGRect tcircle;

        if (distance(POINT(0), POINT(self.points.count - 1)) < 60.0f)

               tcircle = [self centeredRectangle];

 

        // Test 2: Count the distance traveled in degrees. Must fall within 45 degrees of 2 PI

        CGPoint center = CGPointMake(CGRectGetMidX(tcircle), CGRectGetMidY(tcircle));

       float distance = ABS(acos(dotproduct(centerPoint(POINT(0), center), centerPoint(POINT(1), center))));

        for (int i = 1; i < (self.points.count - 1); i++)

               distance += ABS(acos(dotproduct(centerPoint(POINT(i), center), centerPoint(POINT(i+1), center))));

        if ((ABS(distance - 2 * M_PI) < (M_PI / 4.0f))) circle = tcircle;

 

        [self setNeedsDisplay];

}

 

// Show all points plus the current circle and its center

- (void) drawRect: (CGRect) rect

{

        CGContextRef context = UIGraphicsGetCurrentContext();

 

        // draw circle

        [[UIColor redColor] set];

        CGContextAddEllipseInRect(context, circle);

        CGContextStrokePath(context);

 

        // draw center

        CGPoint center = CGPointMake(CGRectGetMidX(circle), CGRectGetMidY(circle));

        CGRect crect = CGRectMake(center.x - 2.0f, center.y - 2.0f, 4.0f, 4.0f);

        CGContextAddEllipseInRect(context, crect);

        CGContextFillPath(context);

 

        // Reset circle

        circle = CGRectZero;

 

        // Show the original shape

        if (self.points.count < 2) return;

        [[UIColor whiteColor] set];

        CGContextSetLineWidth(context, 3.0f);

        for (int i = 0; i < (self.points.count - 1); i++)

        {

               CGPoint pt1 = [[self.points objectAtIndex:i] CGPointValue];

               CGPoint pt2 = [[self.points objectAtIndex:(i+1)] CGPointValue];

               CGContextMoveToPoint(context, pt1.x, pt1.y);

               CGContextAddLineToPoint(context, pt2.x, pt2.y);

               CGContextStrokePath(context);

        }

}

@end

 

@interface TestBedViewController : UIViewController

@end

 

@implementation TestBedViewController

- (void) viewDidLoad

{

        self.navigationController.navigationBar.tintColor = COOKBOOK_PURPLE_COLOR;

        self.view.userInteractionEnabled = YES;

        self.title = @"Circle Maker";

 

        TouchView *tv = [[TouchView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 240.0f, 240.0f)];

        tv.backgroundColor = [UIColor blackColor];

        tv.center = CGPointMake(160.0f, 140.0f);

        [self.view addSubview:tv];

        [tv release];

}

@end

 

@interface TestBedAppDelegate : NSObject <UIApplicationDelegate>

@end

 

@implementation TestBedAppDelegate

- (void)applicationDidFinishLaunching:(UIApplication *)application {

        UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];

        UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:[[TestBedViewController alloc] init]];

        [window addSubview:nav.view];

        [window makeKeyAndVisible];

}

@end

 

int main(int argc, char *argv[])

{

        NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

        int retVal = UIApplicationMain(argc, argv, nil, @"TestBedAppDelegate");

        [pool release];

        return retVal;

}