Randomly generated images

Reprinted Source: http://blog.csdn.net/loverszhaokai/archive/2010/10/04/5921139.aspx

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// If you want to perform verification during login. You only need to determine whether the data entered by the user is equal to the session ["Validate //
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01. Using system;
02. Using system. drawing;
03. Public partial class: system. Web. UI. Page
04 .{
05. // generate a random image background
06. Protected void createimagem (string validatecode)
07 .{
08. // The image width, which is proportional to the Verification code length
09. Int iwidth = (INT) (validatecode. length * 11.5 );
10. // create an image object with a length of 20 and a width of iwidth
11. system. Drawing. bitmap image = new system. Drawing. Bitmap (iwidth, 20 );
12. // create a new Drawing Object
13. Graphics G = graphics. fromimage (image );
14. // font size and font size for drawing
15. Font F = new system. Drawing. Font ("Arial", 10, system. Drawing. fontstyle. Bold );
16. // the size of the paint brush for drawing
17. Brush B = new system. Drawing. solidbrush (color. White );
18. // clear the background color and fill it with a deep olive color
19. G. Clear (color. darkolivegreen );
20. // format the attributes of the brush and draw images within the specified range with the specified brush, color, etc.
21. G. drawstring (validatecode, F, B, 3, 3 );
22. // create a pencil object
23. Pen blackpen = new pen (color. Black, 0 );
24. // create a random object
25. Random Rand = new random ();
26. // draw a line randomly
27. For (INT I = 0; I <5; I ++)
28 .{
29. Int y = Rand. Next (image. Height );
30. // draw a line with a specified pencil. The width is determined by the parameter.
31. G. drawline (blackpen, 0, Y, image. Width, y );
32 .}
33. // output drawing
34. system. Io. memorystream MS = new system. Io. memorystream ();
35. // Save the image to the specified stream
36. image. Save (MS, system. Drawing. imaging. imageformat. JPEG );
37. response. clearcontent ();
38. // configure the output type
39. response. contenttype = "image/JPEG ";
40. // input content
41. response. binarywrite (Ms. toarray ());
42. // clear unnecessary resources
43. G. Dispose ();
44. image. Dispose ();
45 .}
46. // method for generating random characters
47. Protected string createvalidate (INT count)
48 .{
49. string allchar = "1, 2, 3, 4, 5, 6, 7, 8, 9, 0, A, B, C, D, E, F, G, H, I, J, K, L, M, n, O, P, Q, R, S, T, U, V, W, X, Y, Z ";
50. // save all characters in the verification code in a string array
51. String [] allchararray = allchar. Split (',');
52. // initialize a random number
53. String randomcode = "";
54. Int temp =-1;
55. // generate a random object
56. Random Rand = new random ();
57. // cycle based on the number of digits of the Verification Code
58. For (INT I = 0; I <count; I ++)
59 .{
60. // It mainly prevents the same verification code from being generated
61. If (temp! =-1)
62 .{
63. // Add the time scale
64. Rand = new random (I * temp * (INT) datetime. Now. ticks ));
65 .}
66. Int T = Rand. Next (35 );
67. If (temp = T)
68 .{
69. // regenerate if the values are equal
70. Return createvalidate (count );
71 .}
72. Temp = T;
73. randomcode + = allchararray [T];
74 .}
75. // Save the Random verification code in the session
76. session ["valid"] = randomcode;
77. // return the generated random characters
78. Return randomcode;
79 .}
80. Protected void page_load (Object sender, eventargs E)
81 .{
82. createimagem (createvalidate (8 ));
83 .}
84 .}