stanley garvey.com
20th May 2012
The mandelbrot set in C useing X11
/************************************************************************/ /* mandelbrot set generator by Stanley Garvey 2008 */ /* compile using: */ /*cc -I/usr/include/X11 -L/usr/X11/lib -o mandlebrot mandlebrot.c -lX11 */ /************************************************************************/ /* I am going to use the both the Standard input-output and the X Window*/ /* librarys. I need those librarys header files. I include them here */ #include <stdio.h> #include <X11/Xlib.h> /* Now for the program definitions: */ /* I am going to need some boilerplate X definitions */ Display *display; Window window; XSetWindowAttributes attributes; XGCValues gr_values; XFontStruct *fontinfo; GC gr_context; Visual *visual; int depth; int screen; XEvent event; XColor color, dummy; /* I want to use a function for the Attractor so I define it here */ unsigned short int attractor(); /* All C programs need a main function. This is where execution starts */ main (argc, argv) char *argv[]; int argc; { /* I need 2 variables for the X window system */ char *colour; colour="green"; unsigned long forground; forground= 0xff00; /* I am going to map the complex plane onto a window so I need to hold */ /* the horizontal & vertical size of the portion of the complex plane */ /* I am viewing, */ float horizontal_size, vertical_size; /* so that I can map them to the top, bottom, right and left to the */ /* window */ float right, left, top, bottom; float step_real, step_imag; /* Variables for the attractor function */ float j, i; /* Lets make sure that I don't get caught in an infinite loop!! */ unsigned short int iteration_limit=256; /* Set our bail-out value */ /* These are the variables for the window with some defaults filled in */ /*Our drawable area will be 720 pixels wide */ unsigned short int screen_x=720; /*By 540 pixels high */ unsigned short int screen_y=540; /* This is the colour I will draw in */ unsigned short int pix_colour; /* This is where I will Draw */ register int i1, j1; /* These are the defaults for the complex plane, origin centre of the */ /* window, offset by -.6 west */ float origin_x= -.6; float origin_y= 0.0; /* The scale factor will be PI at 100 percent zoom */ float z_range=3.1415927; float percent_zoom=100; horizontal_size=(z_range*100)/percent_zoom; /* Calculate vertical range with a 4:3 aspect ratio */ vertical_size=(horizontal_size)*.8; /* Map complex plane to middle of drawable */ left= origin_x-(horizontal_size/2); right=left+horizontal_size; bottom= origin_y-(vertical_size/2); top=bottom+vertical_size; step_real=horizontal_size/screen_x; step_imag=vertical_size/screen_y; /* Open an X window */ display = XOpenDisplay(NULL); screen = DefaultScreen(display); visual = DefaultVisual(display,screen); depth = DefaultDepth(display,screen); attributes.background_pixel = XBlackPixel(display,screen); window = XCreateWindow( display,XRootWindow(display,screen), 200, 200, screen_x, screen_y, 5, depth, InputOutput, visual ,CWBackPixel, &attributes); XSelectInput(display,window,ExposureMask | KeyPressMask) ; fontinfo = XLoadQueryFont(display,"6x10"); XAllocNamedColor(display, DefaultColormap(display, screen),"red", &color,&dummy); gr_values.font = fontinfo->fid; gr_values.foreground = color.pixel; gr_context=XCreateGC(display,window,GCFont+GCForeground, &gr_values); XFlush(display); XMapWindow(display,window); /* Start mapping the set */ printf("Generating set.\n"); j1=0; for(j=bottom;j<top;(j+=step_imag)) { i1=0; for(i=left;i<right;(i+=step_real)) { /* call the attractor function the colour == number of iterations */ pix_colour=attractor(i, j, iteration_limit); /* I have 77 colours in my palete so I set colour to modulus 78 */ pix_colour=(pix_colour % 78); /* set the colour to a valid X11 named colour */ /* This is a bit clunky and should be rewritten as a function */ switch(pix_colour) { case 0:colour="grey100";break; case 1:colour="grey96";break; case 2:colour="grey92";break; case 3:colour="grey88";break; case 4:colour="grey84";break; case 5:colour="grey80";break; case 6:colour="grey76";break; case 7:colour="grey72";break; case 8:colour="grey68";break; case 9:colour="grey64";break; case 10:colour="grey60";break; case 11:colour="grey56";break; case 12:colour="grey52";break; case 13:colour="grey48";break; case 14:colour="grey46";break; case 15:colour="grey42";break; case 16:colour="grey38";break; case 17:colour="grey36";break; case 18:colour="grey32";break; case 19:colour="grey28";break; case 20:colour="grey26";break; case 21:colour="grey22";break; case 22:colour="grey18";break; case 23:colour="grey16";break; case 24:colour="grey12";break; case 25:colour="NavyBlue";break; case 26:colour="MidnightBlue";break; case 27:colour="DarkSlateBlue";break; case 28:colour="SlateBlue";break; case 29:colour="blue";break; case 30:colour="RoyalBlue";break; case 31:colour="DodgerBlue";break; case 32:colour="DeepSkyBlue";break; case 33:colour="SkyBlue";break; case 34:colour="LightSkyBlue";break; case 35:colour="turquiose";break; case 36:colour="DarkTurquiose";break; case 37:colour="LightGreen";break; case 38:colour="green";break; case 39:colour="SeaGreen";break; case 40:colour="DarkSeaGreen";break; case 41:colour="MediumSeaGreen";break; case 42:colour="LightSeaGreen";break; case 43:colour="DarkYellow";break; case 44:colour="yellow";break; case 45:colour="LightYellow";break; case 46:colour="DarkOrange";break; case 47:colour="orange";break; case 48:colour="LightOrange";break; case 49:colour="DarkGreen";break; case 50:colour="yellow";break; case 51:colour="DarkYellow";break; case 52:colour="orange";break; case 53:colour="DarkOrange";break; case 54:colour="magenta";break; case 55:colour="red";break; case 56:colour="DarkRed";break; case 57:colour="Violetred";break; case 58:colour="purple";break; case 59:colour="cyan";break; case 60:colour="yellow";break; case 61:colour="DarkYellow";break; case 62:colour="orange";break; case 63:colour="DarkOrange";break; case 64:colour="red";break; case 65:colour="DarkRed";break; case 66:colour="VioletRed";break; case 67:colour="DeepPink";break; case 68:colour="purple";break; case 69:colour="cyan";break; case 70:colour="yellow";break; case 71:colour="DarkYellow";break; case 72:colour="MediumVioletRed";break; case 73:colour="PaleVioletRed";break; case 74:colour="OrangeRed";break; case 75:colour="tomato";break; case 76:colour="IndianRed";break; case 77:colour="red";break; default: colour="black"; } /* Block of x Window code to draw the pixel */ XAllocNamedColor(display, DefaultColormap(display, screen),colour, &color,&dummy); gr_values.foreground = color.pixel; gr_context=XCreateGC(display,window,GCFont+GCForeground, &gr_values); XDrawPoint(display,window,gr_context,i1,j1); i1++; } j1++; XFlush(display); } /* Block of x Window code; loops until keypress then closes window */ while(1){ XNextEvent(display,&event); switch(event.type){ case Expose: printf("Set done.\n "); break; case KeyPress: XCloseDisplay(display); exit(0); /* Okay we're done here, nothing to see, move along please */ } } } /* Mandlebrot attractor Function Definition */ unsigned short int attractor(i, j, iteration_limit) /* here we declare our parameters */ /* passed from the calling function */ float i; float j; unsigned short int iteration_limit; { /* our local Variables are declared here */ /* count number of times round the loop */ unsigned short int number_iterations=0; float x, y, x2, y2; /* keep doing the calculation as long as it does not start to aproach */ /* infinity and it has not hit my bail out Value */ while(number_iterations<iteration_limit && (x2+y2)<=4) { y2=(y*y); x2=(x*x); y=(2*x*y)+j; x=(x2-y2)+i; number_iterations++; } /* Not interested in the calculation, */ /* only the number times round the loop */ return(number_iterations); }
