Drawing a Circle with Mid – Point Circle Algorithm in C/C++

As in the previous line drawing algorithm, we sample at unit intervals and determine the closest pixel position to the specified circle path at each step. For a given radius r and screen center position (xc, yc), we can first set up our algorithm to calculate pixel positions around a circle path centered at the coordinate origin (0, 0). Then each calculated  position (x, y) is moved to its proper screen position by adding xc to x and yc to y. Along the circle section from x = 0 to x = y in the first quadrant, the slope of the curve varies from 0 to –1.  Therefore, we can take unit steps in the positive x direction over this octant and use a decision parameter to determine which of the two possible y positions is closer to the circle path at each step. Position in the other seven octants are then obtained by symmetry.

The following section implements Mid – Point Circle  Algorithm in C/C++. The source code is compiled using gcc Compiler and Code::Blocks IDE. To print a pixel, SetPixel() function of windows.h is used.

Note: to run this code in your machine with Code::blocks IDE, add a link library libgdi32.a (it is usually inside MinGWlib )  in linker setting.
Souce Code

Loading...
#include <windows.h>

#include <cmath>

#define ROUND(a) ((int) (a + 0.5))

/* set window handle */

static HWND sHwnd;

static COLORREF redColor=RGB(255,0,0);

static COLORREF blueColor=RGB(0,0,255);

static COLORREF greenColor=RGB(0,255,0);


void SetWindowHandle(HWND hwnd){

    sHwnd=hwnd;

}


/* SetPixel */

void setPixel(int x,int y,COLORREF& color=redColor){

    if(sHwnd==NULL){

        MessageBox(NULL,"sHwnd was not initialized !","Error",MB_OK|MB_ICONERROR);

        exit(0);

    }

    HDC hdc=GetDC(sHwnd);

    SetPixel(hdc,x,y,color);

    ReleaseDC(sHwnd,hdc);

    return;

}


void circlePoints(int xCenter, int yCenter, int x, int y){

    setPixel(xCenter + x, yCenter + y);

    setPixel(xCenter - x, yCenter + y);

    setPixel(xCenter + x, yCenter - y);

    setPixel(xCenter - x, yCenter - y);

    setPixel(xCenter + y, yCenter + x);

    setPixel(xCenter - y, yCenter + x);

    setPixel(xCenter + y, yCenter - x);

    setPixel(xCenter - y, yCenter - x);


}

void drawCircle(int xCenter, int yCenter, int radius){

    int x = 0;

    int y = radius;

    int p = 1 - radius;

    circlePoints(xCenter, yCenter, x, y);

    while(x < y){

        x++;

        if (p < 0){

            p += 2 * x + 1;

        }else{

            y--;

            p += 2 * (x - y) + 1;

        }

        circlePoints(xCenter, yCenter, x, y);

    }

}

/* Window Procedure WndProc */

LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam){

    switch(message){

        case WM_PAINT:

            SetWindowHandle(hwnd);

            drawCircle(200, 200, 100);

            break;

        case WM_CLOSE: // FAIL THROUGH to call DefWindowProc

            break;

        case WM_DESTROY:

            PostQuitMessage(0);

            return 0;

        default:

        break; // FAIL to call DefWindowProc //

    }

    return DefWindowProc(hwnd,message,wParam,lParam);

}



int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int iCmdShow){

    static TCHAR szAppName[] = TEXT("Circle");

    WNDCLASS wndclass;

    wndclass.style         = CS_HREDRAW|CS_VREDRAW ;

    wndclass.lpfnWndProc   = WndProc ;

    wndclass.cbClsExtra    = 0 ;

    wndclass.cbWndExtra    = 0 ;

    wndclass.hInstance     = hInstance ;

    wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;

    wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;

    wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;

    wndclass.lpszMenuName  = NULL ;

    wndclass.lpszClassName = szAppName ;


    // Register the window //

    if(!RegisterClass(&wndclass)){

        MessageBox(NULL,"Registering the class failled","Error",MB_OK|MB_ICONERROR);

        exit(0);

    }


    // CreateWindow //

    HWND hwnd=CreateWindow(szAppName,"Mid Point Circle Drawing - Programming Techniques",

                WS_OVERLAPPEDWINDOW,

                 CW_USEDEFAULT,

                 CW_USEDEFAULT,

                 CW_USEDEFAULT,

                 CW_USEDEFAULT,

                 NULL,

                 NULL,

                 hInstance,

                 NULL);

    if(!hwnd){

        MessageBox(NULL,"Window Creation Failed!","Error",MB_OK);

        exit(0);

    }

    // ShowWindow and UpdateWindow //

    ShowWindow(hwnd,iCmdShow);

    UpdateWindow(hwnd);


    // Message Loop //

    MSG msg;

    while(GetMessage(&msg,NULL,0,0)){

        TranslateMessage(&msg);

        DispatchMessage(&msg);

    }


    /* return no error to the operating system */

    return 0;

}

Output

MidPointCicleAlgorithm

Loading...
SHARE Drawing a Circle with Mid – Point Circle Algorithm in C/C++

You may also like...

5 Responses

  1. your circle mid-point line drawing algorithm when running in code blocks displays two errors in error logs .The errors are given below:
    line 3…..error: cmath: No such file or directory
    line 27…error: expected ';', ',' or ')' before '&' token

  2. Bibek123 says:

    @bishnu:- This is fully tested code. Make your filename .cpp not .c.

  3. Hey there! Would you mind if I share your blog with my twitter group?
    There’s a lot of folks that I think would really appreciate
    your content. Please let me know. Thank you

Leave a Reply

Your email address will not be published. Required fields are marked *

Share