PHP实现生成带背景的图形验证码功能

本文实例讲述了PHP实现生成带背景的图形验证码功能。分享给大家供大家参考，具体如下：

以前我们利用php生成的都是无背景或同一色彩背景的验证码了,但这种验证容易给机器识别了,这里就来介绍一些生成带背景的图形验证码实例.

1、产生一张png的图片,
2、为图片设置背景色,
3、设置字体颜色和样式,
4、产生4位数的随机的验证码,
5、把产生的每个字符调整旋转角度和位置画到png图片上,
6、加入噪点和干扰线防止注册机器分析原图片来恶意注册,
7、输出图片,
8、释放图片所占内存

authcode.php文件,代码如下:

<?php    session_start ();    header ( 'Content-type: image/png' );    //创建图片    $im = imagecreate($x=130,$y=45 );    $bg = imagecolorallocate($im,rand(50,200),rand(0,155),rand(0,155)); //第一次对 imagecolorallocate() 的调用会给基于调色板的图像填充背景色    $fontColor = imageColorAllocate ( $im, 255, 255, 255 );  //字体颜色    $fontstyle = 'rock.ttf';          //字体样式，这个可以从c:windowsFonts文件夹下找到，我把它放到和authcode.php文件同一个目录，这里可以替换其他的字体样式    //产生随机字符    for($i = 0; $i < 4; $i ++) {        $randAsciiNumArray     = array (rand(48,57),rand(65,90));        $randAsciiNum         = $randAsciiNumArray [rand ( 0, 1 )];        $randStr             = chr ( $randAsciiNum );        imagettftext($im,30,rand(0,20)-rand(0,25),5+$i*30,rand(30,35),$fontColor,$fontstyle,$randStr);        $authcode            .= $randStr;    }    $_SESSION['authcode']    = $randFourStr;//用户和用户输入的验证码做比较    //干扰线    for ($i=0;$i<8;$i++){        $lineColor    = imagecolorallocate($im,rand(0,255),rand(0,255),rand(0,255));        imageline ($im,rand(0,$x),0,rand(0,$x),$y,$lineColor);    }    //干扰点    for ($i=0;$i<250;$i++){        imagesetpixel($im,rand(0,$x),rand(0,$y),$fontColor);    }    imagepng($im);    imagedestroy($im);?>

例2,新建一个PHP文件captcha_code_file.php,代码如下:

//首先开启sessionsession_start();//定义前台显示验证码长&宽$image_width = 120;$image_height = 40;$characters_on_image = 6;$font = './monofont.ttf';//The characters that can be used in the CAPTCHA code.//avoid confusing characters (l 1 and i for example)$possible_letters = '23456789bcdfghjkmnpqrstvwxyz';$random_dots = 10;$random_lines = 30;$captcha_text_color="0x142864";$captcha_noice_color = "0x142864";//定义要生成验证码的字符串$code = '';$i = 0;while ($i < $characters_on_image) {$code .= substr($possible_letters, mt_rand(0, strlen($possible_letters)-1), 1);$i++;}$font_size = $image_height * 0.75;$image = @imagecreate($image_width, $image_height);/* setting the background, text and noise colours here */$background_color = imagecolorallocate($image, 255, 255, 255);$arr_text_color = hexrgb($captcha_text_color);$text_color = imagecolorallocate($image, $arr_text_color['red'],    $arr_text_color['green'], $arr_text_color['blue']);$arr_noice_color = hexrgb($captcha_noice_color);$image_noise_color = imagecolorallocate($image, $arr_noice_color['red'],    $arr_noice_color['green'], $arr_noice_color['blue']);/* generating the dots randomly in background */for( $i=0; $i<$random_dots; $i++ ) {imagefilledellipse($image, mt_rand(0,$image_width), mt_rand(0,$image_height), 2, 3, $image_noise_color);}/* generating lines randomly in background of image */for( $i=0; $i<$random_lines; $i++ ) {imageline($image, mt_rand(0,$image_width), mt_rand(0,$image_height), mt_rand(0,$image_width), mt_rand(0,$image_height), $image_noise_color);}/* create a text box and add 6 letters code in it */$textbox = imagettfbbox($font_size, 0, $font, $code);$x = ($image_width - $textbox[4])/2;$y = ($image_height - $textbox[5])/2;imagettftext($image, $font_size, 0, $x, $y, $text_color, $font , $code);/* Show captcha image in the page html page */header('Content-Type: image/jpeg');// defining the image type to be shown in browser widowimagejpeg($image);//showing the imageimagedestroy($image);//destroying the image instance//设置session，做验证$_SESSION['6_letters_code'] = $code;function hexrgb ($hexstr){ $int = hexdec($hexstr); return array("red" => 0xFF & ($int >> 0x10),        "green" => 0xFF & ($int >> 0x8),        "blue" => 0xFF & $int);}