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Mid Point Circle Drawing Algorithm


Mid Point Circle Drawing Algorithm


A circle is made up of 8 Equal Octets so we need to find only coordinates of anyone octet rest we can conclude using that coordinates.
We took octet-2. Where X and Y will represent the pixel
Let us make a function Circle() with parameters coordinates of Centre (Xc, Yc) and pixel point (X, Y) that will plot the pixel on a screen.


We will find pixels assuming that Center is at Origin (0,0) then we will add the coordinates of center to corresponding X and Y while drawing circle on the screen.

Circle (Xc,Yc,X,Y) {

Plot (Y+Xc , X+Yc)         ……Octet-1
Plot (X+Xc , Y+Yc)         ……Octet-2 
Plot (-X+Xc , Y+Yc)        ……Octet-3
Plot (-Y+Xc , X+Yc)        …..Octet-4
Plot (-Y+Xc , -X+Yc)       ……Octet-5
Plot (-X+Xc , -Y+Yc)       ……Octet-6
Plot (X+Xc , -Y+Yc)         ……Octet-7
Plot (Y+Xc , -X+Yc)         ……Octet-8
}
Each plot function is for different octet and will construct the circle while in loop.
Now,
Step 1: Get the Radius of Circle R
             And Coordinates of centre of circle (Xc,Yc).
Step 2: X and Y are going to be plotted points
            Set X=0 and Y=R
Step 3: D = 5/4 - r              (Initial decision Parameter)
Step 4: Plot Circle (Xc,Yc,X,Y)
Step 5: if D < 0 Then
                    D = D+(2*x)+1
                    X=X+1
                    Y=Y
             Else
                    D= D+(2*x)-(2*y)+1
                    X=X+1
                    Y=Y-1
Step 6: Check, if X=Y
                          Goto Step 7
                    Else
                          Goto Step 4
Step 7: Stop/Exit.

More>>
Mid point circle drawing derivation
Program of Bresenhams circle drawing program
Bresenham Line drawing derivation

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