Intersection between two lines in coordinates

Question

I can detect the intersection point of two lines, but if my line don\'t has the length of my screen, it detects the point, where it shouldn\'t be.

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Answer 1

That's the correct equation:

+(CGPoint) intersection2:(CGPoint)u1 u2:(CGPoint)u2 v1:(CGPoint)v1 v2:(CGPoint)v2 {  
    CGPoint ret=u1;  
    double t=((u1.x-v1.x)*(v1.y-v2.y)-(u1.y-v1.y)*(v1.x-v2.x))  
    /((u1.x-u2.x)*(v1.y-v2.y)-(u1.y-u2.y)*(v1.x-v2.x));  
    ret.x+=(u2.x-u1.x)*t;  
    ret.y+=(u2.y-u1.y)*t;  
    return ret;  
}  

Also, you can check this library to calculate line intersections: http://www.cprogramdevelop.com/5045485/