draw line between 2 distance points on android

Question

Lets say we have a 400x800 canvas and I want to draw a line connecting the points P1 (10,10) and P2(500000,800000). As you can see the second point is far outside the canvas boundaries. If I use canvas.darwLine(p1.x, p1.y,p2.x,p2.y,paint) the app freezes and the app becomes unusable. using a clipping doesn't solve the problem, the drawing engine is still trying to draw the pixels to the whole way to the second point

Any suggestions or a workaround?

Answer 1

If P2 is outside the visible area (480x800 in this particular case) then calculate the intersection of this line with border, an then use the intersection point instead of P2.

Answer 2

You can scale down your line, with something like this:

int maxX = 400;
int maxY = 800;

//Calculate how much we have to scale down to fit in the bounds:
float scaleX = (maxX - p1.x)/p2.x;
float scaleY = (maxY - p1.y)/p2.y;

//Get the smallest scale, so that we fit in both axises.
float scale = Math.min(scaleX, scaleY);

//Only scale if we are scaling down. There is no need to make lines smaller than the screen scale up to the screen bounds:
if(scale < 1.0f){
    p2.x *= scale;
    p2.y *= scale;
}

I haven't tried this, so I can't guarantee that it will work.