php - 生成验证码镜像PHP

我想使用PHP imagettftext生成验证码图像。以下是我的代码。它给出一个空图像。我想解决这个问题。

我已经测试了代码，但是尽管我的随机文本被传递给验证码图像生成功能，但无法找到为什么未显示图像的原因。

<?php

    function generateRandomString($length = 10) {
        $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
        $randomString = '';
        for ($i = 0; $i < $length; $i++) {
            $randomString .= $characters[rand(0, strlen($characters) - 1)];
        }
        return $randomString;
    }

    function generateCaptchaImage($text = 'good'){
        echo $text;
        echo 'OK';
        // Set the content-type
        header('Content-Type: image/png');

        $width = 200;
        $height = 30;
        $font = 'ThisisKeSha.ttf';

        // Create the image
        $im = imagecreatetruecolor($width, $height);

        //ADD NOISE - DRAW background squares
        $square_count = 6;
        for ($i = 0; $i < 10; $i++) {
          $cx = (int)rand(0, $width/2);
          $cy = (int)rand(0, $height);
          $h  = $cy + (int)rand(0, $height/5);
          $w  = $cx + (int)rand($width/3, $width);
          imagefilledrectangle($im, $cx, $cy, $w, $h, $white);
        }

        //ADD NOISE - DRAW ELLIPSES
        $ellipse_count = 5;
        for ($i = 0; $i < $ellipse_count; $i++) {
          $cx = (int)rand(-1*($width/2), $width + ($width/2));
          $cy = (int)rand(-1*($height/2), $height + ($height/2));
          $h  = (int)rand($height/2, 2*$height);
          $w  = (int)rand($width/2, 2*$width);
          imageellipse($im, $cx, $cy, $w, $h, $grey);
        }

        // Add the text
        imagettftext($im, 20, 0, 10, 20, $black, $font, $text);

        imagepng($im);

    }

    $randomString = generateRandomString();
    generateCaptchaImage($randomString);

    ?>

最佳答案

从评论中解决


未定义$white和$black。
删除echo $text;和echo 'OK';。
服务器上的ThisisKeSha.ttf是否与此目录相同？


未定义$white和$black。