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iOS 如何判断一个点在圆、方框、三角形区域内?

iOS 如何判断一个点在圆、方框、三角形区域内?

作者: 紧张的牛排 | 来源:发表于2017-03-17 08:31 被阅读528次

    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);
    }
    

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