# Explain DDA (Digital Differential Analyzer) Scan Conversion Algorithm?

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The digital differential analyzer is a scan conversion algorithm based on calculation either y or x using the following equations:

y = m *  x

x =   y / m

Sample the line at unit intervals in one coordinate and determine corresponding integer values nearest the line path for the coordinates

Sample at X intervals ( x = 1) and compute each successive Y value as Yk+1 = Yk + m

For lines with positive slope greater than 1, reverse the roles of X and Y.

Sample at unit Y intervals ( y = 1) and calculate each successive X value as

Xk+1 =  Xk + 1/m

### Algorithm Step by Step

Step 1: Input the line endpoints and store the left endpoint in (x1, y1) and right endpoint in (x2, y2)

Step 2: Calculate the values of   x and   y using   x = xb – xa,   y = yb – ya

Step 3: if the values of x > y assign values of steps as x otherwise the values of steps as y

Step 4: Calculate the values of X increment and Y increment and assign the value x= xa and y = ya

Step 5: for k=1 to steps do X = X + X

increment Y= Y + Y increment

Putpixel(ceil(x), ceil(y),15)

Step 6: End

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