# Diagonal line plotting in C

this is quite a simple problem,what i am trying to do is plot a line between any two points on my image, i can plot horizontal lines fine.

below is the part of my code to for the line...

int x1 = 92, y1 = 35, x2 = 150, y2 = 55;

//line between two points

for (x = x1; x <= x2; x++)
{
y = y1;
y2 = y1 + ((y2-y1)/(x2-x1))*(x2-x1);
//line between two points

for (x = x1; x <= x2; x++)
{
y = y1;
y2 = y1 + ((y2-y1)/(x2-x1))*(x2-x1); ??????
image[x][y] = 255; // red colour component
image[x][y] = 255; // green colour compnent
image[x][y] = 255; // blue colour compnent
}

}

this plots a straight line from points (x1,y1) to (x2, )
however im stuck on the y2 value im not sure on what code to use i know its got somthing to do with the graident?

i also know that....

about a for loop in x running between x1 and x2, and calculating a value of y at each point in x.

Something like

for (x = x1; x <= x2; x++)
{
y = y1 + gradient*(x - x1);
}

Now if the magnitude of the gradient is greater than one you'll need a loop in y calculating x at each point.

And you'll need to check x2 is greater than x1 (and swap them if it's not) or the loop won't work.

any help would be really appericated thanks so much guys!!!!!!