CODEWITHSUNDEEP
objective-c
Sandhya Shettigar
Sandhya Shettigar

Reputation: 299

How to draw free hand line smoothly in objective c?

I hav used uigraphics cgcontext to draw line on touch...but my line is not smooth I mean edges is not smooth so can anybody suggest me how to draw smooth line..?? Here my code what i used to draw line:

/* touchesBegan */
UITouch *touch = [touches anyObject];
lastPoint = [touch locationInView:imagevw];

/* touchesMoved */

CGFloat width = [mySlider value];
UIGraphicsBeginImageContext(imagevw.frame.size);
[imagevw.image drawInRect:CGRectMake(0, 0, imagevw.frame.size.width,imagevw.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), width);
UITouch *touch = [touches anyObject];
mouseSwiped = YES;  
    CGPoint currentPoint = [touch locationInView:imagevw];
    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    imagevw.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
lastPoint = currentPoint;





/*  touchesEnded */
/* same here */ 
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
        CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);`

This is my code and i can draw line free hand but it is not that smooth showing pixels i mean edges not smooth

Upvotes: 3

Views: 4984

Answers (3)

Bhavesh Nayi
Bhavesh Nayi

Reputation: 3656

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{   
    UITouch *touch = [touches anyObject];
    pointCurrent = [touch locationInView:self.view];
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{   
    UITouch *touch = [touches anyObject];
    CGPoint pointNext = [touch locationInView:self.view];
    UIGraphicsBeginImageContext(img.frame.size);
    [img.image drawInRect:CGRectMake(0, 0, img.frame.size.width, img.frame.size.height)];
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 2.0);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0);
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), pointCurrent.x, pointCurrent.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), pointNext.x, pointNext.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    img.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    pointCurrent = pointNext;
}

Upvotes: 1

ingconti
ingconti

Reputation: 11646

is not fluid and smooth using points.. You should use NSBeziePath...

it took 3000 lines but is very smooth, as "bamboo" tool.

The correct approach is using a Bezier path that:

  • records every drawings
  • is used to draw effectively on view
  • you should compute on-fly anchor point for bezier path while tracking (you do NOT draw the touch-point of events)
  • You can even record and save it.

Upvotes: 1

Zeus Alexander
Zeus Alexander

Reputation: 563

This code posted by kyoji works perfectly. You can read the question here:

    CGPoint midPoint(CGPoint p1, CGPoint p2)
{

    return CGPointMake((p1.x + p2.x) * 0.5, (p1.y + p2.y) * 0.5);

}

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

    UITouch *touch = [touches anyObject];

    previousPoint1 = [touch previousLocationInView:self];
    previousPoint2 = [touch previousLocationInView:self];
    currentPoint = [touch locationInView:self];

}

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

    UITouch *touch = [touches anyObject];

    previousPoint2 = previousPoint1;
    previousPoint1 = [touch previousLocationInView:self];
    currentPoint = [touch locationInView:self];


    // calculate mid point
    CGPoint mid1 = midPoint(previousPoint1, previousPoint2); 
    CGPoint mid2 = midPoint(currentPoint, previousPoint1);

    UIGraphicsBeginImageContext(self.imageView.frame.size);
    CGContextRef context = UIGraphicsGetCurrentContext();
    [self.imageView.image drawInRect:CGRectMake(0, 0, self.imageView.frame.size.width, self.imageView.frame.size.height)];

    CGContextMoveToPoint(context, mid1.x, mid1.y);
    // Use QuadCurve is the key
    CGContextAddQuadCurveToPoint(context, previousPoint1.x, previousPoint1.y, mid2.x, mid2.y); 

    CGContextSetLineCap(context, kCGLineCapRound);
    CGContextSetLineWidth(context, 2.0);
    CGContextSetRGBStrokeColor(context, 1.0, 0.0, 0.0, 1.0);
    CGContextStrokePath(context);

    self.imageView.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

}

Upvotes: 5

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