use think\captcha\Captcha;
$captcha = new Captcha();
$captcha->fontSize = 12;
$captcha->length = 4;
$captcha->useNoise = false;
$captcha->codeSet = '2345678';
$captcha->imageW = 87;
$captcha->imageH = 33;
$captcha->bg = [255, 255, 255];
$captcha->reset = false;
return $captcha->entry();
验证时：
$captcha = input('captcha');
$validate = Validate::make([
'captcha|图形验证码' => 'require|captcha'
]);
$data = [
'captcha' => $captcha
];
if (!$validate->check($data)) {
$this->error($validate->getError());
}
报“图形验证码错误”。

这样验证
$captc = new Captcha();
if( !$captc->check($captcha))
{
$this->error('图形验证码错误');
// 验证失败
}
也是报错，

寻求解决办法