Description:
------------
PHP Fatal error:  Invalid opcode 23/16/8. in /wwwroot/web/protected/controller/VerifyController.php on line 41

VerifyController.php文件第41行代码:
imagesetpixel($this->im,$this->width,$this->height,$this->point_color);//生成干扰像素

Test script:
---------------
    function set_point(){
        if(empty($this->point_num)){
            $this->point_num=100;
        }
        for($i=0;$i<$this->point_num;$i++){
            $this->point_color=imagecolorallocate($this->im,mt_rand(0,255),mt_rand(0,255),mt_rand(0,255));//生成干扰像素颜色
            imagesetpixel($this->im,$this->width,$this->height,$this->point_color);//生成干扰像素
        }
    }

Expected result:
----------------
在png画布上生成干扰线，代码在php 7.2.18以下可以正常运行

Actual result:
--------------
环境升级到php7.2.21后该段代码运行报错:
PHP Fatal error:  Invalid opcode 23/16/8.