php调用图像处理的函数_php调用GD库生成验证码的方法

<?php<br>// 启动session用于保存验证码值<br>session_start();<br><br>// 验证码长度<br>$length = 4;<br>// 字符范围<br>$chars = '23456789ABCDEFGHJKLMNPQRSTUVWXYZ';<br>$captcha_text = '';<br><br>// 生成随机字符<br>for ($i = 0; $i < $length; $i++) {<br>    $captcha_text .= $chars[mt_rand(0, strlen($chars) - 1)];<br>}<br><br>// 存入session<br>$_SESSION['captcha'] = $captcha_text;<br><br>// 创建画布<br>$width = 100;<br>$height = 40;<br>$image = imagecreate($width, $height);<br><br>// 分配颜色<br>$bg_color = imagecolorallocate($image, 240, 240, 240); // 背景色<br>$text_color = imagecolorallocate($image, mt_rand(50, 150), mt_rand(50, 150), mt_rand(50, 150)); // 文字色<br><br>// 添加干扰点<br>for ($i = 0; $i < 50; $i++) {<br>    imagesetpixel($image, mt_rand(0, $width), mt_rand(0, $height), $text_color);<br>}<br><br>// 添加干扰线<br>for ($i = 0; $i < 3; $i++) {<br>    $line_color = imagecolorallocate($image, mt_rand(100, 200), mt_rand(100, 200), mt_rand(100, 200));<br>    imageline($image, mt_rand(0, $width), mt_rand(0, $height), mt_rand(0, $width), mt_rand(0, $height), $line_color);<br>}<br><br>// 写入文本（使用内置字体）<br>for ($i = 0; $i < $length; $i++) {<br>    $x = 10 + $i * 20;<br>    $y = mt_rand(15, 25);<br>    imagechar($image, 5, $x, $y, $captcha_text[$i], $text_color);<br>}<br><br>// 输出图像为PNG<br>header('Content-Type: image/png');<br>imagepng($image);<br><br>// 销毁图像资源<br>imagedestroy($image);<br>?>