neiyou_user_web/config/captcha.php

<?php

return [

    'characters' => '123467890',
    //'characters' => '2346789abcdefghjmnpqrtuxyzABCDEFGHJMNPQRTUXYZ',

    'default' => [
        'length' => 4, // 启用科学计算后要改为 9
        'width' => 90,
        'height' => 43,
        'quality' => 90,
        'math' => FALSE, // 改为true，启用科学计算
    ],

    'flat' => [
        'length' => 6,
        'width' => 160,
        'height' => 46,
        'quality' => 90,
        'lines' => 6,
        'bgImage' => FALSE,
        'bgColor' => '#ecf2f4',
        'fontColors' => ['#2c3e50', '#c0392b', '#16a085', '#c0392b', '#8e44ad', '#303f9f', '#f57c00', '#795548'],
        'contrast' => -5,
    ],

    'mini' => [
        'length' => 3,
        'width' => 60,
        'height' => 32,
    ],

    'inverse' => [
        'length' => 5,
        'width' => 120,
        'height' => 36,
        'quality' => 90,
        'sensitive' => TRUE,
        'angle' => 12,
        'sharpen' => 10,
        'blur' => 2,
        'invert' => TRUE,
        'contrast' => -5,
    ]

];