CubicBezierCurve.c

// C program to implement 
// Cubic Bezier Curve 

/* install SDL library for running thing code*/
/* install by using this commamnd line : sudo apt-get install libsdl2-dev */
/* run this code using command : gcc fileName.c -lSDL2 -lm*/

#include<stdio.h> 
#include<stdlib.h> 
#include<math.h> 
#include<SDL2/SDL.h> 

SDL_Window* window = NULL; 
SDL_Renderer* renderer = NULL; 
int mousePosX , mousePosY ; 
int xnew , ynew ; 

/*Function to draw all other 7 pixels present at symmetric position*/
void drawCircle(int xc, int yc, int x, int y) 
{ 
	SDL_RenderDrawPoint(renderer,xc+x,yc+y) ; 
	SDL_RenderDrawPoint(renderer,xc-x,yc+y); 
	SDL_RenderDrawPoint(renderer,xc+x,yc-y); 
	SDL_RenderDrawPoint(renderer,xc-x,yc-y); 
	SDL_RenderDrawPoint(renderer,xc+y,yc+x); 
	SDL_RenderDrawPoint(renderer,xc-y,yc+x); 
	SDL_RenderDrawPoint(renderer,xc+y,yc-x); 
	SDL_RenderDrawPoint(renderer,xc-y,yc-x); 
} 

/*Function for circle-generation using Bresenham's algorithm */
void circleBres(int xc, int yc, int r) 
{ 
	int x = 0, y = r; 
	int d = 3 - 2 * r; 
	while (y >= x) 
	{ 
		/*for each pixel we will draw all eight pixels */
		drawCircle(xc, yc, x, y); 
		x++; 

		/*check for decision parameter and correspondingly update d, x, y*/
		if (d > 0) 
		{ 
			y--; 
			d = d + 4 * (x - y) + 10; 
		} 
		else
			d = d + 4 * x + 6; 
		drawCircle(xc, yc, x, y); 
	} 
} 

/* Function that take input as Control Point x_coordinates and 
Control Point y_coordinates and draw bezier curve */
void bezierCurve(int x[] , int y[]) 
{ 
	double xu = 0.0 , yu = 0.0 , u = 0.0 ; 
	int i = 0 ; 
	for(u = 0.0 ; u <= 1.0 ; u += 0.0001) 
	{ 
		xu = pow(1-u,3)*x[0]+3*u*pow(1-u,2)*x[1]+3*pow(u,2)*(1-u)*x[2] 
			+pow(u,3)*x[3]; 
		yu = pow(1-u,3)*y[0]+3*u*pow(1-u,2)*y[1]+3*pow(u,2)*(1-u)*y[2] 
			+pow(u,3)*y[3]; 
		SDL_RenderDrawPoint(renderer , (int)xu , (int)yu) ; 
	} 
} 
int main(int argc, char* argv[]) 
{ 
	/*initialize sdl*/
	if (SDL_Init(SDL_INIT_EVERYTHING) == 0) 
	{ 
		/* 
			This function is used to create a window and default renderer. 
			int SDL_CreateWindowAndRenderer(int width 
										,int height 
										,Uint32 window_flags 
										,SDL_Window** window 
										,SDL_Renderer** renderer) 
			return 0 on success and -1 on error 
		*/
		if(SDL_CreateWindowAndRenderer(640, 480, 0, &window, &renderer) == 0) 
		{ 
			SDL_bool done = SDL_FALSE; 

			int i = 0 ; 
			int x[4] , y[4] , flagDrawn = 0 ; 

			while (!done) 
			{ 
				SDL_Event event; 

				/*set background color to black*/
				SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE); 
				SDL_RenderClear(renderer); 

				/*set draw color to white*/
				SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE); 

				/* We are drawing cubic bezier curve 
				which has four control points */
				if(i==4) 
				{ 
					bezierCurve(x , y) ; 
					flagDrawn = 1 ; 
				} 

				/*grey color circle to encircle control Point P0*/
				SDL_SetRenderDrawColor(renderer, 128, 128, 128, SDL_ALPHA_OPAQUE); 
				circleBres(x[0] , y[0] , 8) ; 

				/*Red Line between control Point P0 & P1*/
				SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE); 
				SDL_RenderDrawLine(renderer , x[0] , y[0] , x[1] , y[1]) ; 

				/*grey color circle to encircle control Point P1*/
				SDL_SetRenderDrawColor(renderer, 128, 128, 128, SDL_ALPHA_OPAQUE); 
				circleBres(x[1] , y[1] , 8) ; 

				/*Red Line between control Point P1 & P2*/
				SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE); 
				SDL_RenderDrawLine(renderer , x[1] , y[1] , x[2] , y[2]) ; 

				/*grey color circle to encircle control Point P2*/
				SDL_SetRenderDrawColor(renderer, 128, 128, 128, SDL_ALPHA_OPAQUE); 
				circleBres(x[2] , y[2] , 8) ; 

				/*Red Line between control Point P2 & P3*/
				SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE); 
				SDL_RenderDrawLine(renderer , x[2] , y[2] , x[3] , y[3]) ; 

				/*grey color circle to encircle control Point P3*/
				SDL_SetRenderDrawColor(renderer, 128, 128, 128, SDL_ALPHA_OPAQUE); 
				circleBres(x[3] , y[3] , 8) ; 

				/*We are Polling SDL events*/
				if (SDL_PollEvent(&event)) 
				{ 
					/* if window cross button clicked then quit from window */
					if (event.type == SDL_QUIT) 
					{ 
						done = SDL_TRUE; 
					} 
					/*Mouse Button is Down */
					if(event.type == SDL_MOUSEBUTTONDOWN) 
					{ 
						/*If left mouse button down then store 
						that point as control point*/
						if(event.button.button == SDL_BUTTON_LEFT) 
						{ 
							/*store only four points 
							because of cubic bezier curve*/
							if(i < 4) 
							{ 
								printf("Control Point(P%d):(%d,%d)\n"
								,i,mousePosX,mousePosY) ; 

								/*Storing Mouse x and y positions 
								in our x and y coordinate array */
								x[i] = mousePosX ; 
								y[i] = mousePosY ; 
								i++ ; 
							} 
						} 
					} 
					/*Mouse is in motion*/
					if(event.type == SDL_MOUSEMOTION) 
					{ 
						/*get x and y positions from motion of mouse*/
						xnew = event.motion.x ; 
						ynew = event.motion.y ; 

						int j ; 

						/* change coordinates of control point 
						after bezier curve has been drawn */
						if(flagDrawn == 1) 
						{ 
							for(j = 0 ; j < i ; j++) 
							{ 
								/*Check mouse position if in b/w circle then 
						change position of that control point to mouse new 
								position which are coming from mouse motion*/
								if((float)sqrt(abs(xnew-x[j]) * abs(xnew-x[j]) 
									+ abs(ynew-y[j]) * abs(ynew-y[j])) < 8.0) 
								{ 
									/*change coordinate of jth control point*/
									x[j] = xnew ; 
									y[j] = ynew ; 
									printf("Changed Control Point(P%d):(%d,%d)\n"
										,j,xnew,ynew) ; 
								} 
							} 
						} 
						/*updating mouse positions to positions 
						coming from motion*/
						mousePosX = xnew ; 
						mousePosY = ynew ; 
					} 
				} 
				/*show the window*/
				SDL_RenderPresent(renderer); 
			} 
		} 
		/*Destroy the renderer and window*/
		if (renderer) 
		{ 
			SDL_DestroyRenderer(renderer); 
		} 
		if (window) 
		{ 
			SDL_DestroyWindow(window); 
		} 
	} 
	/*clean up SDL*/
	SDL_Quit(); 
	return 0; 
}