Examples:
Input: For line segment between (2, 2) and (6, 6) : we need (3, 3) (4, 4) and (5, 5) as our intermediate points. Input: For line segment between (0, 2) and (0, 6) : we need (0, 3) (0, 4) and (0, 5) as our intermediate points.
For using graphics functions, our system output screen is treated as a coordinate system where the coordinate of the top-left corner is (0, 0) and as we move down our y-ordinate increases and as we move right our x-ordinate increases for any point (x, y).
Now, for generating any line segment we need intermediate points and for calculating them we have can use a basic algorithm called DDA(Digital differential analyzer) line generating algorithm.
DDA Algorithm:
Consider one point of the line as (X0,Y0) and the second point of the line as (X1,Y1).
// calculate dx , dy
dx = X1 - X0;
dy = Y1 - Y0;
// Depending upon absolute value of dx & dy
// choose number of steps to put pixel as
// steps = abs(dx) > abs(dy) ? abs(dx) : abs(dy)
steps = abs(dx) > abs(dy) ? abs(dx) : abs(dy);
// calculate increment in x & y for each steps
Xinc = dx / (float) steps;
Yinc = dy / (float) steps;
// Put pixel for each step
X = X0;
Y = Y0;
for (int i = 0; i <= steps; i++)
{
putpixel (X,Y,WHITE);
X += Xinc;
Y += Yinc;
}
