php图片验证码函数实现扭曲字符的实现代码

3. /**

4. * CaptchaImage() - 创建扭曲字符的验证码图片
5. * $session_name string 验证码图片创建时所需生成Session的变量名
6. * $width int 验证图片的宽度，默认120，注：图片高度与宽度比例相对固定
7. * $noise int 干扰素的点数，默认0
8. * $disturb int 干扰字符个数，默认0
9. * $curve bool 是否增加干扰曲线，默认ture
10. * */
11. function CaptchaImage($session_name = '', $width = 120, $noise = 0, $disturb = 0, $curve = true){
12. $im_x = $width;
13. $im_y = ceil(0.25 * $width);
14. $im = imagecreatetruecolor($im_x, $im_y);
15. $text_c = ImageColorAllocate($im, mt_rand(0, 100), mt_rand(0, 100), mt_rand(0, 100));
16. $gray_rand = mt_rand(160, 220);
17. $buttum_c = ImageColorAllocate($im, $gray_rand, $gray_rand, $gray_rand);
18. imagefill($im, 0, 0, $buttum_c);

19. session_start();

20. $text = '';
21. $characters = 'ABCEFGHJKLMNPQRSTUVWXYZ';
22. for($i = 0, $len = strlen($characters); $i $text .= $characters{rand(0, $len - 1)};
23. if(isset($session_name{0}) && session_start()){
24. $_SESSION[$session_name] = $text;
25. $_SESSION['CaptchaSessionTime'] = time();
26. }
27. }

28. $font = 'arial.ttf';

29. $size = floor(0.2 * $width);

30. $ttfbox = imagettfbbox($size, 0, $font, $text);

31. $text_width = abs($ttfbox[2] - $ttfbox[0]);
32. $side = floor(($im_x - $text_width) / 2);

33. $array = array(-1, 1);

34. for ($i = 0; $i $p = array_rand($array);
35. $an = $array[$p] * mt_rand(5, 10); // 字符倾斜角度
36. imagettftext($im, $size, $an, $side + $i * ($size - 1), $im_y - 3, $text_c, $font, $text{$i});
37. }

38. $distortion_im = imagecreatetruecolor ($im_x, $im_y);

39. imagefill($distortion_im, 0, 0, $buttum_c);
40. $distortion = floor(0.04 * $width); // 扭曲程度
41. for ($i = 0; $i for ($j = 0; $j $rgb = imagecolorat($im, $i , $j);
42. if( (int)($i + sin($j / $im_y * 2 * M_PI) * $distortion) = 0 ){
43. imagesetpixel($distortion_im, (int)($i + sin($j / $im_y * 2 * M_PI - M_PI * 0.1) * $distortion) , $j, $rgb);
44. }
45. }
46. }

47. if($disturb > 0){

48. $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
49. for($i = 0; $i imagestring($distortion_im, 3, mt_rand(-10, $im_x), mt_rand(-10, $im_y), $chars[mt_rand(0, 35)], $text_c);
50. }
51. }

52. //加入干扰象素;

53. if($noise > 0){
54. for($i = 0; $i $randcolor = ImageColorallocate($distortion_im, mt_rand(0,255), mt_rand(0,255), mt_rand(0,255));
55. imagesetpixel($distortion_im, mt_rand()%$im_x , mt_rand()%$im_y , $randcolor);
56. }
57. }

58. // 加干扰曲线

59. if($curve){
60. $rand = mt_rand(5, 30);
61. $rand1 = mt_rand(15, 25);
62. $rand2 = mt_rand(5, 10);
63. for ($yy = $rand; $yy for ($px = -60; $px $x = $px / $rand1;
64. $y = ($x != 0) ? sin($x) : $y;
65. $py = $y * $rand2;
66. imagesetpixel($distortion_im, $px + 60, $py + $yy, $text_c);
67. }
68. }
69. }

70. //设置文件头;

71. Header("Content-type: image/JPEG");

72. //以PNG格式将图像输出到浏览器或文件;

73. ImagePNG($distortion_im);

74. //销毁一图像，释放与image关联的内存;

75. ImageDestroy($distortion_im);
76. ImageDestroy($im);
77. }

78. CaptchaImage('code', 100); //生成一张图片 并将随机数字存放到key为code的session中

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