Circle, arc, pieslice are declared as follows:

Declaration:

*  void far arc(int x, int y, int stangle, int endangle, int radius);
*  void far circle(int x, int y, int radius);
*  void far pieslice(int x, int y, int stangle, int endangle, int radius);

Remarks:

* arc draws a circular arc in the current drawing color.
* circle draws a circle in the current drawing color.
* pieslice draws a pie slice in the current drawing color, then fills it using
the current fill pattern and fill color.

Arguments:

* (x,y): Center point of arc, circlew, or pie slice
* stangle: Start angle in degrees
* endangle: End angle in degrees
* radius: Radius of arc, circle, and pieslice

Here, stangle and endangle are in degrees starting from the +ve x-axis in the polar coordinate system in the anti-clockwise direction. if stangle is 0, endangle is 360, it will draw a full circle. Refer this figure for clear idea: For the details of current color, fill color and fill patterns, refer the sections Lines and Colors.

Angle calculations

Another basic shape that we come across is a rectangle. To draw a border, use rectangle with the coordinates of outline, to draw a square use rectangle with same height and width. drawpoly() and fillpoly() are two functions useful to draw any polygons. To use these functions, store coordinates of the shape in an array and pass the address of array as an argument to the function. By looking at the output of the previous program, you can understand what drawpoly is. fillpoly is similar except that it fills in the shape with current fill color.

Declaration:

*   void far rectangle(int left, int top, int right, int bottom);
*   void far drawpoly(int numpoints, int far *polypoints);
*   void far fillpoly(int numpoints, int far *polypoints);

Remarks:

*  Rectangle draws a rectangle in the current line style, thickness, and drawing color.
*  Drawpoly draws a polygon using the current line style and color.
*  Fillpoly draws the outline of a polygon using the current line style and color, then fills the polygon using the current fill pattern and fill color.

Arguments:

*  (left,top) is the upper left corner of the rectangle, and (right,bottom) is its lower right corner.
*  numpoints:  Specifies number of points
*  Polypoints: Points to a sequence of (numpoints x 2) integers. Each pair of integers gives the x and y coordinates of a point on the polygon.

To draw a closed polygon with N points, numpoints should be N+1 and the array polypoints[] should contain 2(N+1) integers with first 2 integers equal to last 2 integers.

Let us study more about shapes latter. Here is some idea about colors. There are 16 colors declared in graphics.h as listed bellow.

BLACK            : 0
BLUE              : 1
GREEN           : 2
CYAN             : 3
RED               : 4
MAGENTA      : 5
BROWN         : 6
LIGHTGRAY   : 7
DARKGRAY   : 8
LIGHTBLUE    : 9
LIGHTGREEN : 10
LIGHTCYAN   : 11
LIGHTRED     : 12
LIGHTMAGENTA  : 13
YELLOW        : 14
WHITE           : 15

To use these colors, use functions setcolor(), setbkcolor() and setfillstyle(). setcolor() function sets the current drawing color. If we use setcolor(RED); and draw any shape, line or text after that, the drawing will be in red color. You can either use color as defined above or number like setcolor(4);. setbkcolor() sets background color for drawing. Setfillstyle sets fill pattern and fill colors. After calling setfillstyle, if we use functions like floodfill, fillpoly, bar etc, shpes will be filled with fill color and pattern set using setfillstyle. These

function declarations are as follows.
Declaration:

*  void far setfillstyle(int pattern, int color);
*  void far setcolor(int color);
*  void far setbkcolor(int color);

Remarks:

* setfillstyle sets the current fill pattern and fill color.
* setcolor sets the current drawing color to color, which can range from 0 to getmaxcolor.
* setbkcolor sets the background to the color specified by color.

The parameter pattern in setfillstyle is as follows:

Parameter pattern in setfillstyle

Here is an example program with colors, pixels, bar, cleardevice etc. stdlib.h is used for random number generation. We have a function random(no), it returns a random number between 0 an no. The effect is by drawing random radius, random color circles with same center and random pixels. kbhit() function(defined in conio.h) returns a nonzero value when a key is pressed in the keyboard. So, the loop will continue until a key is pressed.

/*
random.c
some graphics effects using random numbers.
example 1.2
by HarshaPerla, http://eharsha.tk
*/

#include “graphics.h”
#include “conio.h”
#include “stdlib.h”

void main()
{
int gd,gm;
gd=DETECT;

initgraph(&gd, &gm, “”);
setcolor(3);
setfillstyle(SOLID_FILL,RED);
bar(50, 50, 590, 430);

setfillstyle(1, 14);
bar(100, 100, 540, 380);

while(!kbhit())
{
putpixel(random(439)+101,  random(279)+101,random(16));
setcolor(random(16));
circle(320,240,random(100));
}
getch();
closegraph();
}