c - C 语言的 GD 验证码生成器

Question

我正在用 C 语言为我的网站编写一个 fastcgi 应用程序。

如何使用GD生成验证码图像？

我在谷歌上徒劳地搜索了一些东西(搜索仍在进行中)，但如果有人能给我有关该过程的基本概念，那就太好了。

对于随机数，我将使用纳秒作为种子(或使用它本身)。

提前致谢。

Answer 1

查看 void gdImageStringUp(gdImagePtr im, gdFontPtr font, int x, int y, unsigned char *s, int color) (FUNCTION) 代码示例(您几乎可以复制粘贴它) )..

  #include "gd.h"
  #include "gdfontl.h"
  #include <string.h>

  /*... inside a function ...*/
  gdImagePtr im;
  int black;
  int white;
  /* String to draw. */
  char *s = "Hello.";
  im = gdImageCreate(100, 100);
  /* Background color (first allocated) */
  black = gdImageColorAllocate(im, 0, 0, 0);
  /* Allocate the color white (red, green and blue all maximum). */
  white = gdImageColorAllocate(im, 255, 255, 255);
  /* Draw a centered string going upwards. Axes are reversed,
  and Y axis is decreasing as the string is drawn. */
  gdImageStringUp(im, gdFontGetLarge(),
  im->w / 2 - gdFontGetLarge()->h / 2,
  im->h / 2 + (strlen(s) * gdFontGetLarge()->w / 2), s, white);
  /* ... Do something with the image, such as
  saving it to a file... */
  /* Destroy it */
  gdImageDestroy(im);

http://www.libgd.org/Font

噪声是通过随机像素/线条/等完成的，这很简单:

  /*... inside a function ...*/
  gdImagePtr im;
  int black;
  int white;
  im = gdImageCreate(100, 100);
  /* Background color (first allocated) */
  black = gdImageColorAllocate(im, 0, 0, 0);
  /* Allocate the color white (red, green and blue all maximum). */
  white = gdImageColorAllocate(im, 255, 255, 255);
  /* Set a pixel near the center. */
  gdImageSetPixel(im, 50, 50, white);
  /* ... Do something with the image, such as
  saving it to a file... */
  /* Destroy it */
  gdImageDestroy(im);

http://www.libgd.org/Drawing

LibGD 在他们的网站上有无数的例子。