iOS 如何判断一个点在圆、方框、三角形区域内?
如何判断一个点是不是在方框(CGRect)、圆(Circle)、三角形(Triangle)内呢?
1.方框
//苹果官方方法可以判断
+ (BOOL)point:(CGPoint)point inSquareArea:(CGRect)rect {
return CGRectContainsPoint(rect, point);
}
2.圆
//圆心到点的距离>?半径
+ (BOOL)point:(CGPoint)point inCircleRect:(CGRect)rect {
CGFloat radius = rect.size.width/2.0;
CGPoint center = CGPointMake(rect.origin.x + radius, rect.origin.y + radius);
double dx = fabs(point.x - center.x);
double dy = fabs(point.y - center.y);
double dis = hypot(dx, dy);
return dis <= radius;
}
3.三角形
//点都否在三边线的右边?这个应该不是最优解
+ (BOOL)point:(CGPoint)point inTriangleVertexPointsArea:(NSArray<NSValue *> *)vertexPoints {
if (vertexPoints.count == 3) {
CGPoint point0 = [vertexPoints[0] CGPointValue];
CGPoint point1 = [vertexPoints[1] CGPointValue];
CGPoint point2 = [vertexPoints[2] CGPointValue];
BOOL b0 = [self sign:point point1:point0 point2:point1] < 0.0f;
BOOL b1 = [self sign:point point1:point1 point2:point2] < 0.0f;
BOOL b2 = [self sign:point point1:point2 point2:point0] < 0.0f;
return ((b0 == b1) && (b1 == b2));
}
return NO;
}
+ (CGFloat)sign:(CGPoint)point0 point1:(CGPoint)point1 point2:(CGPoint)point2 {
return (point0.x - point2.x) * (point1.y - point2.y) - (point1.x - point2.x) * (point0.y - point2.y);
}