Implement touches methods to the curve drawn by bezier curve

Question

如何在iPad中实现贝塞尔曲线绘制的曲线上的触摸。

Answer 1

You can use the containsPoint: method of UIBezierPath to work out if a touch is within a curve. However this only works if the path is of a closed type eg a circle or rectangle.

One thing i have never tested is if a path is implicitly closed by an invisible line from start point to end point. As in 3 sides of a polygon can detect a hit within the 4 sides when the 4th side doesn't exist except in your imagination.

For the case where the curve is a single stroke (as in a painting program) you will have to artificially expand the stroke to detect your touch. One way to achieve this is run tangents from each end and draw a parallel line of the same shape along the curve most vector programs do when you request "expand line/stroke" then you can detect a hit within that expanded stroke. The fatness of your expanded stroke will determine how accurate the touch has to be.