#include <stdio.h>
 int main() {
        const int dimx = 800; 
        const int dimy = 800;
        int i, j;
        FILE * fp = fopen("first.ppm", "wb"); /* b - tryb binarny */
        fprintf(fp, "P6\n%d %d\n255\n", dimx, dimy);
        for(j=0; j<dimy; ++j){
          for(i=0; i<dimx; ++i){         
                        static unsigned char color[3];
                        color[0]=i % 255; /* red */
                        color[1]=j % 255; /* green */
                        color[2]=(i*j) % 255; /* blue */
                        fwrite(color,1,3,fp);
                }
        }
        fclose(fp);
        return 0;
 }

/*

How do I get the length of a dynamically allocated array in C? You can't.  You have to pass the length as a parameter to your function.
https://stackoverflow.com/questions/5126353/get-the-length-of-dynamically-allocated-array-in-c


--------------


gcc p.c -Wall -lm

./a.out

ls -l *.ppm


*/

#include <stdio.h>
#include <string.h> // strncat
#include <stdlib.h> // malloc
#include <math.h> // log10

// color = RGB triplet = (thus three bytes per pixel) in the order red, green, then blue
// color = 3 bytes
// color component ( channel) = 1 byte =  number from 0 to 255 = unsigned char 


// size of virtual 2D array of pixels
// each piexel has a RGB color
int iWidth = 1000;
int iHeight ; // 


// size of the dynamic 1D array 
unsigned char * data;
size_t ColorSize = 3; // RGB = number of color components = channels
size_t ArrayLength; // number of 1D array's elements = ENumber = iWidth*iHeight*ColorSize
size_t ElementSize; // size of array's element in bytes
size_t ArraySize; // size of array in bytes = ElementSize*ArrayLength 


size_t HeaderSize ; // size of the P6 file  header in bytes
size_t FileSize; // = HeaderSize +ArraySize [bytes]



// --------------- save dynamic "A" array of uinsigned char to the binary ppm file ( P6 ) --------------------------------
int SaveArray2PPM (unsigned char A[], size_t ESize, size_t ALength,  int k)
{

  FILE *fp;
  const unsigned int MaxColorComponentValue = 255;	/* color component is coded from 0 to 255 ;  it is 8 bit color file */
  
  char name [100]; /* name of file */
  snprintf(name, sizeof name, "%d", k); /*  */
  char *filename =strncat(name,".ppm", 4);
  
  

  /* save image to the pgm file  */
  fp = fopen (filename, "wb");	/*create new file,give it a name and open it in binary mode  */
  if (fp == NULL) 
  	{	printf("File open error"); 
  		return 1;}
  	else {
  		fprintf (fp, "P6\n%u %d\n%d\n", iWidth, iHeight, MaxColorComponentValue);	/*write header to the file */
  		fwrite (A, ESize, ALength, fp);	// write dynamic A array to the binary file in one step  = fwrite (A , ESize, ALength, fp);
 
  		printf ("File %s saved. \n", filename);
  		fclose (fp);
  		return 0;}
  
}



int setup(){

	iHeight = iWidth; // quadratic 2D array
	// 1D array
	ArrayLength = iWidth*iHeight*ColorSize;
	ElementSize = sizeof(unsigned char);
	ArraySize = ElementSize*ArrayLength ; 
	HeaderSize = 11 + (size_t) (log10(iHeight) +log10(iWidth)); 
	
	FileSize = HeaderSize + ArraySize; 
	
	/* create dynamic 1D array for RGB colors  */
  	data = malloc (ArraySize);
  	if (data == NULL ){
    		printf ( "Could not allocate memory for the array\n");
    		return 1;}

	
	return 0;
}


void info(){

	printf("ppm (P6) header size = %zu bytes\n", HeaderSize);
	printf("Array Size  = %zu bytes\n", ArraySize);
	printf("PPM file size  = %zu bytes\n", FileSize);

	
}



int end(){


  printf (" allways free memory (deallocate )  to avoid memory leaks \n"); // https://en.wikipedia.org/wiki/C_dynamic_memory_allocation
  free (data);
  info();
  return 0;

}



// ================================== main ============================================

int main (){

	setup();
	SaveArray2PPM(data, ElementSize, ArrayLength, 1);
	end();

	return 0;
}

/*  

c console program based on :
cpp code by Claudio Rocchini

http://commons.wikimedia.org/wiki/File:Poincare_halfplane_eptagonal_hb.svg


http://validator.w3.org/ 
The uploaded document "circle.svg" was successfully checked as SVG 1.1. 
This means that the resource in question identified itself as "SVG 1.1" 
and that we successfully performed a formal validation using an SGML, HTML5 and/or XML 
Parser(s) (depending on the markup language used). 

*/

#include <stdio.h>
#include <stdlib.h>
#include <math.h>



const double PI = 3.1415926535897932384626433832795;

const int  iXmax = 1000,
           iYmax = 1000,
           radius=100,
           cx=200,
           cy=200;
const char *black="#FFFFFF", /* hexadecimal number as a string for svg color*/
           *white="#000000";
           
 FILE * fp;

void draw_circle(FILE * FileP,int radius,int cx,int cy)
{
    fprintf(FileP,"<circle cx=\"%f\" cy=\"%f\" r=\"%f\" style=\"stroke:%s; stroke-width:2; fill:%s\"/>\n",
    cx,cy,radius,white,black);
}

void beginSVG(

int main(){
    FILE * fp;
    char *filename="circle.svg";
    fp = fopen(filename,"w");
	char *comment = "<!-- sample comment in SVG file  \n can be multi-line -->";

	fprintf(fp,
		    "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n"
		    "%s \n "
           "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\" \n"
           "\"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n"
           "<svg width=\"20cm\" height=\"20cm\" viewBox=\"0 0 %f %f \"\n"
           " xmlns=\"http://www.w3.org/2000/svg\" version=\"1.1\">\n",
           comment,iXmax,iYmax);


	draw_circle(fp,radius,cx,cy);
	

	
    
    
    fprintf(fp,"</svg>\n");
	fclose(fp);
	printf(" file %s saved \n",filename ); 
	getchar();
	return 0;
}

 
               #include <stdio.h>
               #include "dislin.h"
               main()
               {
                 disini ();
                 messag ("This is a test", 100, 100);
                 disfin ();
               }

#include "cpgplot.h"
#include "math.h"

int main()
{
   int i;
   float xs[9], ys[9];
   float xr[101], yr[101];

   /* Compute numbers to be plotted. */

   for (i=0; i<101; i++) {
     xr[i] = 0.1*i;
     yr[i] = xr[i]*xr[i]*exp(-xr[i]);
   }
   for (i=0; i<9; i++) {
     xs[i] = i+1;
     ys[i] = xs[i]*xs[i]*exp(-xs[i]);
   }

   /* Open graphics device. */

   if (cpgopen("?") < 1)
     return 1;

   /* Define coordinate range of graph (0 < x < 10, 0 < y < 0.65),
      and draw axes. */

   cpgenv(0., 10., 0., 0.65, 0, 0);
   
   /* Label the axes (note use of \\u and \\d for raising exponent). */
   
   cpglab("x", "y", "PGPLOT Graph: y = x\\u2\\dexp(-x)");

   /*  Plot the line graph. */
    
   cpgline(101, xr, yr);

   /* Plot symbols at selected points. */

   cpgpt(9, xs, ys, 18);

   /* Close the graphics device */

   cpgclos();
   return 0;
}

#include <stdio.h>
#include <stdlib.h>
int main(void) {
  int i;
  double x,y;
  char *output_filename="data.txt";
  FILE *output_file;
  output_file = fopen(output_filename, "w");  
  if (output_file  == NULL) {
    fprintf(stderr, "Nie moge otworzyc %s\n", output_filename);
    getchar();
    return 1;

  } else {
    /* nagłówek */
    fprintf(output_file,"%s %s      %s \n","#","x","y");
    y = 0.005;
    x = 0.0;
    /* 2 kolumny liczb rozdzielone spacjami */
    fprintf(output_file,"% 6.2f % 6.2f \n",x,y);
    for(i=0;i<5;++i) {
      x += y;
      /* 2 kolumny liczb rozdzielone spacjami */
      fprintf(output_file,"% 6.2f % 6.2f \n",x,y);
    }; /* for(i */
  }; /* if ((output_file ... else */
  fclose(output_file);

  fprintf(stderr,"file saved");
  getchar();
  
  
  return 0;
}

int SaveFiles(double A[Length][2], int p)
{

  int p;
  int i;
  char name [30]; /* name of the file */
  char *filename;
  FILE * fp;

 // save ray from A array to the text file
 sprintf(name,"Ray%d", p); /* create name from number */
 filename =strcat(name,".dat");
 fp= fopen(filename,"wb"); /*create new file,give it a name and open it in binary mode  */
 fprintf(fp ,"%s %s      %s \n","#","x","y");
 for (i=0; i<Length ; ++i) fprintf(fp ,"% 1.12f % 1.12f \n",A[i][0],A[i][1]);
 fclose(fp);
 printf("file %s  saved \n", filename);
  
 return 0;
}

char name [100]; /* name of file */
  snprintf(name, sizeof name, "%d", k); /*  */
  char *filename =strncat(name,".ppm", 4);

#include <gtk/gtk.h>

int main(int argc, char* argv[])
{
  GtkWidget* window;

  gtk_init(&argc, &argv);

  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title(GTK_WINDOW(window), "GTK+");
  gtk_window_set_position(GTK_WINDOW(window), GTK_WIN_POS_CENTER);

  gtk_widget_show(window);

  g_signal_connect(G_OBJECT(window), "destroy", G_CALLBACK(gtk_main_quit), NULL);

  gtk_main();

  return 0;
}

#include <QtGui>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QLabel label("Hello, world!");
    label.show();
    return app.exec();
}

#include<GL/glut.h> 

void main(int argc, char**argv) { 
    glutInit(&argc, argv); 
    glutInitWindowPosition(100,100); 
    glutInitWindowSize(500,500); 
    glutCreateWindow(“Hello World”); 
    glutMainLoop(); 
}