确定线是否与CGRect相交 [英] Determine if line intersects CGRect

问题描述

我正在寻找类似这样的东西：

  CGPoint startLine = CGPointMake（5.0f，5.0f）; 
 CGPoint endLine = CGPointMake（25.0f，25.0f）; 
 
 CGRect intersectingRect = CGRectMake（10.0f，10.0f，50.0f，50.0f）; 
 
 if（CGRectContainsLine（intersectingRect，startLine，endLine））{// true 
 //线与矩形相交
} 
  

解决方案

没有内置内容，但是应该这样做：

  BOOL RectContainsLine（CGRect r，CGPoint lineStart，CGPoint lineEnd）
 {
 BOOL（^ LineIntersectsLine）（CGPoint，CGPoint，CGPoint，CGPoint）= ^ BOOL （CGPoint line1Start，CGPoint line1End，CGPoint line2Start，CGPoint line2End）
 {
 CGFloat q = 
 //线条起始行之间的距离乘以line2的水平长度
（line1Start.y -  line2Start.y）*（line2End.x  -  line2Start.x）
 //线条起始列之间的距离乘以line2的垂直长度
  - （line1Start.x  -  line2Start.x）*（line2End。 y  -  line2Start.y）; 
 CGFloat d = 
 //第1行的水平长度乘以第2行的垂直长度
（line1End.x  -  line1Start.x）*（line2End.y  -  line2Start.y）
 / / Line 1的垂直长度乘以第2行的水平长度
  - （line1End.y  -  line1Start.y）*（line2End.x  -  line2Start.x）; 
 
 if（d == 0）
 return NO; 
 
 CGFloat r = q / d; 
 
q = 
 //线条起始行之间的距离乘以第1行的水平长度
（line1Start.y  -  line2Start.y）*（line1End.x  -  line1Start.x） 
 //线条起始列之间的距离乘以第1行的垂直长度
  - （line1Start.x  -  line2Start.x）*（line1End.y  -  line1Start.y）; 
 
 CGFloat s = q / d; 
 if（r <0 || r> 1 || s <0 || s> 1）
 return NO; 
 
返回YES; 
}; 
 
 / *测试该线是否与以下任何一个相交：
 *  - 矩形的底部边缘
 *  - 矩形的右边缘
 *  - 顶部矩形的边缘
 *  - 矩形的左边缘
 *  - 矩形的内部（两个点都在里面）
 * / 
 
 return（LineIntersectsLine lineStart，lineEnd，CGPointMake（r.origin.x，r.origin.y），CGPointMake（r.origin.x + r.size.width，r.origin.y））|| 
 LineIntersectsLine（lineStart， lineEnd，CGPointMake（r.origin.x + r.size.width，r.origin.y），CGPointMake（r.origin.x + r.size.width，r.origin.y + r.size.height）） || 
 LineIntersectsLine（lineStart，lineEnd，CGPointMake（r.origin.x + r.size.width，r.origin.y + r.size.height），CGPointMake（r.origin.x，r.origin .y + r.size.height））|| 
 LineIntersectsLine（lineStart，lineEnd，CGPointMake（r.origin.x，r.origin.y + r.size.height），CGPointMake（r.origin.x ，r.origin.y））|| 
（CGRectC ontainsPoint（r，lineStart）&& CGRectContainsPoint（r，lineEnd）））; 
} 
  

从这个问题中移出：如何知道一条线是否与矩形相交

What is the most efficient way to determine if a line intersects a rectangle?

I'm looking for something similar to this:

CGPoint startLine = CGPointMake(5.0f,5.0f);
CGPoint endLine = CGPointMake(25.0f,25.0f);

CGRect intersectingRect = CGRectMake(10.0f,10.0f,50.0f,50.0f);

if (CGRectContainsLine(intersectingRect,startLine,endLine)) { //true
    //line intersects rectangle
}

解决方案

There's nothing built in, but this ought to do it:

BOOL RectContainsLine(CGRect r, CGPoint lineStart, CGPoint lineEnd)
{
    BOOL (^LineIntersectsLine)(CGPoint, CGPoint, CGPoint, CGPoint) = ^BOOL(CGPoint line1Start, CGPoint line1End, CGPoint line2Start, CGPoint line2End)
    {
        CGFloat q =
            //Distance between the lines' starting rows times line2's horizontal length
            (line1Start.y - line2Start.y) * (line2End.x - line2Start.x)
            //Distance between the lines' starting columns times line2's vertical length
            - (line1Start.x - line2Start.x) * (line2End.y - line2Start.y);
        CGFloat d =
            //Line 1's horizontal length times line 2's vertical length
            (line1End.x - line1Start.x) * (line2End.y - line2Start.y)
            //Line 1's vertical length times line 2's horizontal length
            - (line1End.y - line1Start.y) * (line2End.x - line2Start.x);

        if( d == 0 )
            return NO;

        CGFloat r = q / d;

        q =
            //Distance between the lines' starting rows times line 1's horizontal length
            (line1Start.y - line2Start.y) * (line1End.x - line1Start.x)
            //Distance between the lines' starting columns times line 1's vertical length
            - (line1Start.x - line2Start.x) * (line1End.y - line1Start.y);

        CGFloat s = q / d;
        if( r < 0 || r > 1 || s < 0 || s > 1 )
            return NO;

        return YES;
    };

    /*Test whether the line intersects any of:
     *- the bottom edge of the rectangle
     *- the right edge of the rectangle
     *- the top edge of the rectangle
     *- the left edge of the rectangle
     *- the interior of the rectangle (both points inside)
     */

    return (LineIntersectsLine(lineStart, lineEnd, CGPointMake(r.origin.x, r.origin.y), CGPointMake(r.origin.x + r.size.width, r.origin.y)) ||
            LineIntersectsLine(lineStart, lineEnd, CGPointMake(r.origin.x + r.size.width, r.origin.y), CGPointMake(r.origin.x + r.size.width, r.origin.y + r.size.height)) ||
            LineIntersectsLine(lineStart, lineEnd, CGPointMake(r.origin.x + r.size.width, r.origin.y + r.size.height), CGPointMake(r.origin.x, r.origin.y + r.size.height)) ||
            LineIntersectsLine(lineStart, lineEnd, CGPointMake(r.origin.x, r.origin.y + r.size.height), CGPointMake(r.origin.x, r.origin.y)) ||
            (CGRectContainsPoint(r, lineStart) && CGRectContainsPoint(r, lineEnd)));
}

Trivially ported from this question: How to know if a line intersects a rectangle

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