Graphics library in C

问题:

I was wondering if there were any good free graphics libraries for C that are easy to use? It's for plotting 2d and 3d graphs and then saving to a file. It's on a Linux system and there's no gnuplot on the system right now.

Or would it just be simpler to switch to another language, and if so which one would be easy to learn?

回答1:

To plot 2D and 3D graphs in C I would recommend the library DISLIN. You can see examples here or there.

The code is pretty easy to use and gives nice results.

回答2:

I like the Cairo library. It has a nice interface to C and it can output in many formats.

回答3:

This question is a bit vague, "graphics" is a wide field. You can get pretty far using just plain SDL, but it might also be considered "too low-level". You need to provide more requirements.

回答4:

There's Clutter. Here are a few snippets from the about page:

"Clutter is an open source software library for creating fast, visually rich, portable and animated graphical user interfaces."

"Clutter aims to be non specific — it implements no particular User Interface style, but rather provides a rich generic foundation that facilitates rapid and easy creation of higher level tool kits tailored to specific needs."

"Developed in C, with language bindings for Perl, Python, C#, C++, Vala and Ruby."

"Scene-graph of layered 2D interface elements manipulated in 3D space via position, grouping, transparency, scaling, clipping and rotation."

I haven't tried it out myself, but it seems pretty flexible if you are looking for something just to play around with.

回答5:

I've used netpbm format a few time when I needed something simple.

That's how I found out that qsort() (in my implementation and for the data provided) performs a merge sort!

Source code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#define ARRAY_SIZE 20
#define MAX_VALUE 10

unsigned char arr[ARRAY_SIZE];

void print_array(const void *left, const void *right) {
  static int imgs = 0;
  int k, j;
  FILE *img;
  char fname[100];
  char rgb[100];

  if (++imgs > 9999) return;
  sprintf(fname, "img/img%04d.ppm", imgs);
  /* create image in "img/" directory */
  img = fopen(fname, "w");
  if (img) {
    fprintf(img, "P3\n%d %d\n255\n", ARRAY_SIZE, MAX_VALUE);
    for (j=0; j<MAX_VALUE; j++) {
      for (k=0; k<ARRAY_SIZE; k++) {
        int colour = 0;
        if (left && left == arr+k) colour = 2;
        if (right && right == arr+k) colour = 2;
        if (arr[k] == MAX_VALUE - j - 1) colour = 1;
        switch (colour) {
          default: sprintf(rgb, "%d %d %d", 255, 255, 255); break;
          case 1: sprintf(rgb, "%d %d %d", 0, 0, 0); break;
          case 2: sprintf(rgb, "%d %d %d", 255, 0, 0); break;
        }
        }
        fprintf(img, "%s\n", rgb);
      }
    }
    fclose(img);
  } else {
    perror("img fopen");
  }
}

int cmp(const void *left, const void *right) {
  const unsigned char a = *(const unsigned char*)left;
  const unsigned char b = *(const unsigned char*)right;

  print_array(left, right);
  if (a < b) return -1;
  if (a == b) return 0;
  return 1;
}

int main(void) {
  int k;
  unsigned int seed = 0; /* or time(0) */

  srand(seed);
  for (k=0; k<ARRAY_SIZE; k++) {
    arr[k] = rand() % MAX_VALUE;
  }
  print_array(NULL, NULL);
  qsort(arr, (size_t)ARRAY_SIZE, sizeof *arr, cmp);
  print_array(NULL, NULL);
  /* use imagemagick to convert group of files to .gif */
  system("convert -delay 0"
         " img/img*.ppm"
         " -loop 1 img/libc-qsort2.gif");
  /* remove .ppm files */
  system("rm img/" "*ppm"); /* ... my editor does not like a
                                   slash and a star together,
                                   even inside quotes */

  return 0;
}

回答6:

I recommend the Qt GUI toolkit, coupled with the open-source QwtPlot and QwtPlot3D. It's implemented in C++, easy-to-use, extensible, and free...

回答7:

Take a look at PGPLOT. It's old but works great and should be in the repos. PLPLOT is also an option, it's similar and newer and should also be readily available in the repos. They're both extremely powerful and can do what you specified.

回答8:

Most people use the gd library for rendering from C but you must implement the "math plotting" part.