How to stroke the dotted lines using cgcontext iOS?

Question

I have drawn the path using cgpoints but the path is full of dotted lines.I want to stroke the dashed line.

My code:

CGPoint Point1=CGPointMake(184.9489, 383.4082);
CGPoint Point2=CGPointMake(184.9489, 383.4082);
CGPoint Point3=CGPointMake(184.2969, 377.911);
CGPoint Point4=CGPointMake(184.2969, 377.911);
CGPoint Point5=CGPointMake(184.2443, 372.978);
CGPoint Point6=CGPointMake(184.2443, 372.978);
NSArray *arry1=[NSArray arrayWithObjects:[NSNumber numberWithFloat:Point1.x],[NSNumber numberWithFloat:Point3.x],[NSNumber numberWithFloat:Point5.x],nil];
NSArray *arry2=[NSArray arrayWithObjects:[NSNumber numberWithFloat:Point1.y],[NSNumber numberWithFloat:Point3.y],[NSNumber numberWithFloat:Point5.y],nil];
NSArray *arry3=[NSArray arrayWithObjects:[NSNumber numberWithFloat:Point2.x],[NSNumber numberWithFloat:Point4.x],[NSNumber numberWithFloat:Point6.x],nil];
NSArray *arry4=[NSArray arrayWithObjects:[NSNumber numberWithFloat:Point2.y],[NSNumber numberWithFloat:Point4.y],[NSNumber numberWithFloat:Point6.y],nil];
for(int i=0;i<[arry2 count];i++)
{
    UIGraphicsBeginImageContext(self.view.frame.size);
    [img_View.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 3 );
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetStrokeColorWithColor(UIGraphicsGetCurrentContext(),
                                     [UIColor blueColor].CGColor);
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), [[arry1 objectAtIndex:i]floatValue], [[arry2 objectAtIndex:i]floatValue]);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), [[arry3 objectAtIndex:i]floatValue], [[arry4 objectAtIndex:i]floatValue]);
    CGContextSetBlendMode(UIGraphicsGetCurrentContext(),kCGBlendModeColor);
    CGContextDrawPath(UIGraphicsGetCurrentContext(), kCGPathFillStroke);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    img_View.image = UIGraphicsGetImageFromCurrentImageContext();
    [img_View setAlpha:1];
    UIGraphicsEndImageContext();}

the o/p is:(vertically 3 dots). the expected result:combining those three points. Can anyone please provide me some information regarding this? Thanks in advance.

Answer 1

The problem is in each loop, the start point and end point of the line is the same point, so it draws as a dot. If you log the point values you will see it. The following code will draw 2 lines.

UIGraphicsBeginImageContext(self.view.frame.size);
[_imageView.image drawInRect:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];

CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(context, 3.0);
CGContextSetLineCap(context, kCGLineCapRound);
CGContextSetStrokeColorWithColor(context,
                                 [UIColor greenColor].CGColor);

for(int i=0;i<arry2.count;i++)
{
    if (i == 0)
    CGContextMoveToPoint(context,[[arry1 objectAtIndex:i]floatValue] ,[[arry2 objectAtIndex:i]floatValue]);
    CGContextAddLineToPoint(context, [[arry3 objectAtIndex:i]floatValue], [[arry4 objectAtIndex:i]floatValue]);
}
CGContextSetBlendMode(context,kCGBlendModeColor);
CGContextDrawPath(context, kCGPathFillStroke);
CGContextStrokePath(context);

_imageView.image = UIGraphicsGetImageFromCurrentImageContext();
[_imageView setAlpha:1];
UIGraphicsEndImageContext();