Question

I want to make a smoother line which I draw by getting the points on touch.
The line is a drawing, but with corners. I am using quad function to draw the curve, but the curve sometimes has corners in it when the points are near to each other. What could be done to figure out the solution for this problem?

Answer 1

I deliberately didn’t answer this question earlier, because you are using Android API and Quad function, and i thought there would be a way to increase the no. of points in the Quadratic Bezier Curve it is drawing. I did a google, and didn’t find anything myself, but i was waiting for someone to post a trick using Android API.

It seems that the smoothness will have to be achieved manually by drawing a higher resolution Bezier Curve using code:
Quad function is drawing the Quadratic Bezier Curve, here is a good link for algorithm to draw Bezier Curves, all you have to do is to increase the no. of points in your curve:
Formula of Quadratic Bezier Curve is: `

[x,y]=(1 – t) 2P0 + 2(1 – t)tP1 + t2P2

`And you have to make t smaller to make the loop iterate more, so there will be more points and you’ll be able to draw a smoother curve.

Here is the code that is interesting (I have slightly changed it to make it simpler for me to explain):

double t = 0;

Point prevPoint = CalculateBezierPoint(t, p0, p1, p2, p3);
for(int i = 0; i <= 100; i++)
{
  Point nextPoint = CalculateBezierPoint(t, p0, p1, p2, p3); //see this part from the link i have given

  //Draw line from previous point to next point.
  prevPoint = nextPoint;
  t = t + (1/100)    
}

To make a smoother curve, increase the number of segments in the for loop (1000 etc, experiment with it), also change this line t = t + (1/100) (divide the value by the larger no. of segments you choose, the i

Use this solution as a last option, if you find a way to do it using Android API, please post it here as well, and if someone else has a way to do it, please post, i am waiting for answers.