生成验证码字符

[HttpGet("safecode")]
public async Task<ActionResult> GetCode()
{
   var safeCode=await RsCode.VerifyCodeHelper.GetSingleObj().CreateVerifyCodeAsync(RsCode.VerifyCodeHelper.VerifyCodeType.AbcVerifyCode);
   return File( RsCode.VerifyCodeHelper.GetSingleObj().CreateByteByImgVerifyCode(safeCode, 110, 30),@"image/png");
}