贝塞尔曲线
2016-12-06 本文已影响14人
VegetableAD
维基百科上的解释:
三角函数将直角三角形的内角和它的两个边的比值相关联,也可以等价地用与单位圆有关的各种线段的长度来定义。常见的三角函数包括正弦函数 余弦函数和正切函数
Image.png如图,在直角三角形中仅有锐角(大小在0到90度之间的角)三角函数的定义
。给定一个锐角⍬,可以做出一个直角三角形,使得其中的一个内角是⍬。设这个三角形中,⍬的对边、邻边和斜边长度分别是a,b,h,那么
⍬的正弦是对边与斜边的比值:
⍬的余弦是邻边与斜边的比值:
⍬的正切是对边与邻边的比值:
⍬的余切是邻边与对边的比值:
⍬的正割是斜边与邻边的比值:
⍬的余割是斜边与对边的比值:
医生讲解的非常详细:mask一下
http://www.jianshu.com/p/55c721887568
自己的小🌰,有些地方带优化。
public class PushBezierView extends View implements View.OnTouchListener{
private Path mPath;
private Paint circlePaint;
private Paint pathPaint;
int width,height;
float setPointX = 80,setPointY = 80;
float movePointX = 100,movePointY = 100;
int moveRadius = 40;
int originRadius = 40;
float previousRelativeDistance;
public PushBezierView(Context context) {
this(context,null);
}
public PushBezierView(Context context, AttributeSet attrs) {
this(context, attrs,0);
}
public PushBezierView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
circlePaint = new Paint(Paint.ANTI_ALIAS_FLAG);
circlePaint.setColor(Color.RED);
circlePaint.setStyle(Paint.Style.FILL);
pathPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
pathPaint.setColor(Color.RED);
pathPaint.setStyle(Paint.Style.FILL);
mPath = new Path();
setOnTouchListener(this);
}
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
width = w;
height = h;
setPointX = width / 2;
setPointY = height / 4;
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (originRadius < 0){
canvas.drawCircle(movePointX, movePointY, moveRadius, circlePaint);
}else {
float dx = movePointX - setPointX;
float dy = movePointY - setPointY;
float relativeDistance = Math.abs(Math.max(dx, dy));
if (relativeDistance > previousRelativeDistance) {
originRadius = originRadius - (int) (relativeDistance / 50);
} else {
originRadius = originRadius + (int) (relativeDistance / 50);
}
canvas.drawCircle(setPointX, setPointY, originRadius, circlePaint);
canvas.drawCircle(movePointX, movePointY, moveRadius, circlePaint);
mPath.reset();
float controlX = (movePointX + setPointX) / 2;
float controlY = (movePointY + setPointY) / 2;
double q = Math.atan(dx / dy);
double absoluteX = Math.cos(q) * moveRadius;
double absoluteY = Math.sin(q) * moveRadius;
double originAbsoluteX = Math.cos(q) * originRadius;
double originAbsoluteY = Math.sin(q) * originRadius;
float firstX = setPointX - (float) originAbsoluteX;
float firstY = setPointY + (float) originAbsoluteY;
mPath.moveTo(firstX, firstY);
float secondX = movePointX - (float) absoluteX;
float secondY = movePointY + (float) absoluteY;
mPath.quadTo(controlX, controlY, secondX, secondY);
float thridX = movePointX + (float) absoluteX;
float thridY = movePointY - (float) absoluteY;
mPath.lineTo(thridX, thridY);
float fourX = setPointX + (float) originAbsoluteX;
float fourY = setPointY - (float) originAbsoluteY;
mPath.quadTo(controlX, controlY, fourX, fourY);
mPath.close();
canvas.drawPath(mPath, pathPaint);
previousRelativeDistance = relativeDistance;
}
}
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()){
case MotionEvent.ACTION_MOVE:
if (moveRadius > 0) {
movePointX = event.getX();
movePointY = event.getY();
invalidate();
}
break;
case MotionEvent.ACTION_UP:
if (originRadius < 0 && moveRadius > 0){
ValueAnimator valueAnimator = ValueAnimator.ofInt(40,0);
valueAnimator.setInterpolator(new DecelerateInterpolator());
valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
moveRadius = (int)animation.getAnimatedValue();
invalidate();
}
});
valueAnimator.start();
}
}
return true;
}
}