problem in drawing line - iphone

Question

brushSize=1.0f;
UIGraphicsBeginImageContext(self.view.frame.size);
[drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)]; //originally self.frame.size.width, self.frame.size.height)];
CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapButt); //kCGLineCapSquare, kCGLineCapButt, kCGLineCapRound
CGContextSetLineWidth(UIGraphicsGetCurrentContext(), brushSize);
CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 1.0, 0.0, 1.0);
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x+brushSize*4,lastPoint.y-brushSize);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x-brushSize, lastPoint.y+brushSize*4);
CGContextStrokePath(UIGraphicsGetCurrentContext());
CGContextFlush(UIGraphicsGetCurrentContext());
drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
I am using this Code for drawing......In touchesmoved.
i do getting gaps when iam drawing fastly... what to do?

Answer 1

You should use UITouch's previousLocationInView: method to get the previous known point you finger was and draw a line between that point and the current location.
Another solution is to keep the currentPoint in a static variable between two calls.

Answer 2

CGContextBeginPath(Mycontext);
CGContextMoveToPoint(Mycontext, lastPoint.x, lastPoint.y);
int x, cx, deltax, xstep,y, cy, deltay, ystep,error, st, dupe;
int x0, y0, x1, y1;
x0 = currentPoint.x;
y0 = currentPoint.y;
x1 = lastPoint.x;
y1 = lastPoint.y;
// find largest delta for pixel steps
st = (abs(y1 - y0) > abs(x1 - x0));
// if deltay > deltax then swap x,y
if (st) {
(x0 ^= y0); (y0 ^= x0); (x0 ^= y0); // swap(x0, y0);
(x1 ^= y1); (y1 ^= x1); (x1 ^= y1); // swap(x1, y1);
}
deltax = abs(x1 - x0);
deltay = abs(y1 - y0);
error = (deltax / 2);
y = y0;
if (x0 > x1) { xstep = -1; }
else { xstep = 1; }
if (y0 > y1) { ystep = -1; }
else { ystep = 1; }
for ((x = x0); (x != (x1 + xstep)); (x += xstep))
{
(cx = x); (cy = y); // copy of x, copy of y
// if x,y swapped above, swap them back now
if (st) { (cx ^= cy); (cy ^= cx); (cx ^= cy); }
(dupe = 0); // initialize no dupe
if(!dupe) {
CGContextMoveToPoint(UIGraphicsGetCurrentContext(), cx+brushSize*4,cy-brushSize);
CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), cx-brushSize, cy+brushSize*4);
}
(error -= deltay); // converge toward end of line
if (error < 0) { // not done yet
(y += ystep);
(error += deltax);
}
}
CGContextStrokePath(Mycontext);
Image_Cookie.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
lastPoint = currentPoint;