PHP Generate image Verification Code _php tutorial

PHP Generate Image Verification code

Verification codes are important in Web applications and are often used to prevent users from maliciously submitting forms, such as malicious registration and login, malicious forum flooding, and so on. This article will explain the use of PHP to generate common verification code

Let's take a look at the general effect.

So the next step is to put the code directly.

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$image = Imagecreatetruecolor (100, 30); Create a canvas $imagecolor = Imagecolorallocate ($image, 255, 255, 255); Background color Imagefill ($image, 0, 0, $imagecolor); Fill background color for ($i =0; $i <4; $i + +) {//Loop 4-digit $fontsize = 6; $fontcolor = Imagecolorallocate ($image, rand (0, $), rand (0, $), rand (0, 200)); $fontcontent = rand (0, 9); $x = $i *100/4 + rand (5, 15); $y = rand (5, 10); Imagestring ($image, $fontsize, $x, $y, $fontcontent, $fontcolor); } for ($i =0; $i <200; $i + +) {//loop Add interference point $pointcolor = Imagecolorallocate ($image, Rand (), Rand (50, 200)); $x = rand (1, 99); $y = rand (1, 29); Imagesetpixel ($image, $x, $y, $pointcolor); } for ($i =0; $i <3; $i + +) {//loop Add interference line $linecolor = Imagecolorallocate ($image, rand (+), rand (100, 250)); $x 1 = rand (1, 25); $x 2 = rand (50, 75); $y 1 = rand (1, 15); $y 2 = rand (15, 25); Imageline ($image, $x 1, $y 1, $x 2, $y 2, $linecolor); } Header ("Content-type:image/png"); Imagepng ($image); Imagedestroy ($image); ?>

And then we'll share one. Can generate Chinese code

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1.qi Enable GD Library GD library provides a series of APIs for working with images, using the GD library to process pictures, or to create images. The GD library on the site is often used to generate thumbnails or to add watermarks to images or generate reports on site data. Session_Start (); The GBK encoded string into the UTF-8 string, the first argument is written GBK because the php file stored in the host encoding is GBK encoded UTF-8 encoding Browser Universal support, strong versatility, this translates into UTF-8 $str = Iconv ("GBK", "Utf-8", "The mortal life of the Green Mountains and monuments open heart will clouds unroll happiness will always accompany you"); if (!is_string ($str) | |!mb_check_encoding ($STR, "Utf-8")) { Exit ("Not a string or not a utf-8"); } $zhongwenku _size; To get the length of a string by UTF-8 encoding $zhongwenku _size = Mb_strlen ($str, "UTF-8"); Import the above characters into the array $zhongwenku = Array (); for ($i =0; $i < $zhongwenku _size; $i + +) { $zhongwenku [$i] = Mb_substr ($str, $i, 1, "UTF-8"); } $result = ""; Four characters to write on a picture for ($i =0; $i <4; $i + +) { Switch (rand (0, 1)) { Case 0: $result. = $zhongwenku [rand (0, $zhongwenku _size-1)]; Break Case 1: $result. =dechex (rand (0,15)); Break } } $_session["Check"] = $result; Create a true Color picture width 100, Height 30 $img = Imagecreatetruecolor (100, 30); Assigning background colors $BG = imagecolorallocate ($img, 0, 0, 0); Assigning text colors $te = Imagecolorallocate ($img, 255,255,255); Write a string on a picture Imagestring ($img, Rand (3,8), Rand (1,70), Rand (1,10), $result, $te); A special font can be written on a picture based on the loaded font Imagettftext ($IMG, Max, Rand (2, 9), $te, "Msyh." TTF ", $result); $_session["Check"] = $result; for ($i =0; $i <3; $i + +) { $t = Imagecolorallocate ($img, rand (0, 255), rand (0, 255), rand (0, 255)); Draw Line Imageline ($img, 0, rand (0,), rand (70,100), rand (0,), $te); } $t = Imagecolorallocate ($img, rand (0, 255), rand (0, 255), rand (0, 255)); Add noise to a picture for ($i =0; $i <200; $i + +) { Imagesetpixel ($img, rand (1, +), rand (1,), $t); } Send HTTP header information specifies that the JPEG in image is sent this time Header ("Content-type:image/jpeg"); Output JPEG image to browser Imagejpeg ($IMG); ?>

One more example.

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Session_Start (); function Random ($len) { $srcstr = "1A2S3D4F5G6HJ8K9QWERTYUPZXCVBNM"; Mt_srand (); $strs = ""; for ($i = 0; $i < $len; $i + +) { $strs. = $srcstr [Mt_rand (0, 30)]; } return $strs; } Randomly generated string $STR = random (4); Verify the width of the code picture $width = 50; Verify the height of the code picture $height = 25; Declare the picture format of the layer you want to create @ Header ("Content-type:image/png"); Create a layer $im = Imagecreate ($width, $height); Background color $back = Imagecolorallocate ($im, 0xFF, 0xFF, 0xFF); Blur Point Color $pix = Imagecolorallocate ($im, 187, 230, 247); Font Color $font = Imagecolorallocate ($im, 41, 163, 238); The point of painting blur function Mt_srand (); for ($i = 0; $i < $i + +) { Imagesetpixel ($im, Mt_rand (0, $width), Mt_rand (0, $height), $pix); } Output character Imagestring ($im, 5, 7, 5, $STR, $font); Output Rectangle Imagerectangle ($im, 0, 0, $width-1, $height-1, $font); Output picture Imagepng ($im); Imagedestroy ($im); $STR = MD5 ($STR); Select a cookie Setcookie ("Verification", $str, Time () + 7200, "/"); Select Session $_session["verification"] = $STR; ?>

The next thing you can do is call it in the page:

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If you want to achieve the "can't see" effect, add the following JS to the page

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function changing () { document.getElementById (' Checkpic '). src= "/images/checkcode.php?" +math.random (); }

The above mentioned is the whole content of this article, I hope you can like.

http://www.bkjia.com/PHPjc/1013643.html www.bkjia.com true http://www.bkjia.com/PHPjc/1013643.html techarticle PHP generated Image verification Code verification code is very important in Web applications, and is often used to prevent users from maliciously submitting forms, such as malicious registration and login, forum malicious irrigation and so on. This article will be explained by examples ...

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