我正在使用USB摄像头制作车牌识别系统。摄像机将扫描车牌号，并在标签上显示其详细信息。但是，如果摄像机没有扫描/检测到任何车牌，我希望系统显示警告错误，以表明摄像机没有识别出任何东西。我正在使用C＃进行编码。如果摄像机未检测到任何牌照，您能帮助我如何显示警告的代码！
private FilterInfoCollection CaptureDevices;
private VideoCaptureDevice videoSource;
private Int32 pictureCount = 0;
private DateTime parkDate, parkTime;
private static readonly HttpClient client = new HttpClient();
List<Image> images;
List<Result> results;
private void Form1_Load(object sender, EventArgs e)
{
CaptureDevices = new FilterInfoCollection(FilterCategory.VideoInputDevice);
foreach (FilterInfo Device in CaptureDevices)
{
cboDevice.Items.Add(Device.Name);
}
cboDevice.SelectedIndex = 0;
videoSource = new VideoCaptureDevice();
timer1.Tick += new EventHandler(this.Timer1_Tick);
timer1.Interval = (600) * (100);
timer1.Enabled = true;
timer1.Start();
videoSource = new VideoCaptureDevice(CaptureDevices[cboDevice.SelectedIndex].MonikerString);
videoSource.NewFrame += new NewFrameEventHandler(videoSource_NewFrame);
videoSource.Start();
cboParkNo.SelectedIndex = 0;
}
void videoSource_NewFrame(object sender, AForge.Video.NewFrameEventArgs eventArgs)
{
pbImage.Image = (Bitmap)eventArgs.Frame.Clone();
}
public static async Task<string> ProcessImage(string image_path)
{
string SECRET_KEY = "**";
Byte[] bytes = File.ReadAllBytes(image_path);
string imagebase64 = Convert.ToBase64String(bytes);
var content = new StringContent(imagebase64);
var response = await client.PostAsync("https://api.openalpr.com/v2/recognize_bytes?recognize_vehicle=1&country=my&secret_key=" + SECRET_KEY, content).ConfigureAwait(false);
var buffer = await response.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
var byteArray = buffer.ToArray();
var responseString = Encoding.UTF8.GetString(byteArray, 0, byteArray.Length);
return responseString;
}
private void Timer1_Tick(object sender, EventArgs e)
{
pbImage.Image.Save(pictureCount.ToString() + ".jpg", ImageFormat.Jpeg);
Task<string> recognizeTask = Task.Run(() => ProcessImage(@"C:\Users\User\source\repos\CatcityLPR\bin\Debug\" + pictureCount.ToString() + ".jpg"));
recognizeTask.Wait();
string task_result = recognizeTask.Result;
RootObject vehicresult = JsonConvert.DeserializeObject<RootObject>(task_result);
if (vehicresult.results.Count == 0)
{
lblWarning.Text = "License plate cannot be recognized!";
lblDate.Text = DateTime.Now.ToString("MMddyyyy");
lblTime.Text = DateTime.Now.ToShortTimeString();
}
else
{
txtPlateNo.Text = vehicresult.results[0].plate.ToString();
lblDate.Text = DateTime.Now.ToString("MMddyyyy");
lblTime.Text = DateTime.Now.ToShortTimeString();
parkDate = Convert.ToDateTime(lblDate.Text);
parkTime = Convert.ToDateTime(lblTime.Text);
SqlConnection conn = new SqlConnection(new DBConnection().ConnectionString);
if (conn.State == System.Data.ConnectionState.Closed)
conn.Open();
SqlDataReader dr;
SqlCommand cmd = new SqlCommand("SELECT * FROM pmsVehicleRecord WHERE clVehicPlateNo='" + txtPlateNo.Text + "'", conn);
dr = cmd.ExecuteReader();
if (dr.HasRows)
{
while (dr.Read())
{
lblFullName.Text = dr["clFullName"].ToString();
lblUsername.Text = dr["clUsername"].ToString();
lblAddress.Text = dr["clAddress"].ToString();
lblPaymentMethod.Text = dr["clPaymentMethod"].ToString();
}
dr.Close();
SqlCommand cms = new SqlCommand("SELECT * FROM pmsParkingRecord WHERE parkVehicPlateNo ='" + txtPlateNo + "' AND parkDate='" + lblDate + "'", conn);
dr = cms.ExecuteReader();
if (dr.HasRows)
{
dr.Close();
SqlCommand cmt = new SqlCommand("UPDATE pmsParkingRecord SET parkExitTime='" + parkTime + "'");
cmt.Connection = conn;
if (conn.State == System.Data.ConnectionState.Closed)
conn.Open();
SqlDataReader ds = cmt.ExecuteReader();
}
else
{
dr.Close();
SqlCommand cmn = new SqlCommand("INSERT INTO pmsParkingRecord (parkUsername, parkFullName, parkAddress, parkVehicPlateNo, parkPaymentMethod, parkDate, parkEntryTime) VALUES ('" + lblUsername.Text + "', '" + lblFullName.Text + "', '" + lblAddress.Text + "', '" + txtPlateNo.Text + "', '" + lblPaymentMethod.Text + "', '" + parkDate + "', '" + parkTime + "')");
cmn.Connection = conn;
if (conn.State == System.Data.ConnectionState.Closed)
conn.Open();
SqlDataReader ds = cmn.ExecuteReader();
}
}
else
{
lblWarning.Text = "License Plate No is not registered!";
btnEntry.Enabled = false;
btnExit.Enabled = false;
}
dr.Close();
}
pictureCount++;
}
RootObject.cs
namespace CatcityLPR
{
public class ProcessingTime
{
public double total { get; set; }
public double plates { get; set; }
public double vehicles { get; set; }
}
public class VehicleRegion
{
public int y { get; set; }
public int x { get; set; }
public int height { get; set; }
public int width { get; set; }
}
public class Candidate
{
public int matches_template { get; set; }
public string plate { get; set; }
public double confidence { get; set; }
}
public class Coordinate
{
public int y { get; set; }
public int x { get; set; }
}
public class Orientation
{
public double confidence { get; set; }
public string name { get; set; }
}
public class Color
{
public double confidence { get; set; }
public string name { get; set; }
}
public class Make
{
public double confidence { get; set; }
public string name { get; set; }
}
public class BodyType
{
public double confidence { get; set; }
public string name { get; set; }
}
public class Year
{
public double confidence { get; set; }
public string name { get; set; }
}
public class MakeModel
{
public double confidence { get; set; }
public string name { get; set; }
}
public class Vehicle
{
public List<Orientation> orientation { get; set; }
public List<Color> color { get; set; }
public List<Make> make { get; set; }
public List<BodyType> body_type { get; set; }
public List<Year> year { get; set; }
public List<MakeModel> make_model { get; set; }
}
public class Result
{
public string plate { get; set; }
public double confidence { get; set; }
public int region_confidence { get; set; }
public VehicleRegion vehicle_region { get; set; }
public string region { get; set; }
public int plate_index { get; set; }
public double processing_time_ms { get; set; }
public List<Candidate> candidates { get; set; }
public List<Coordinate> coordinates { get; set; }
public Vehicle vehicle { get; set; }
public int matches_template { get; set; }
public int requested_topn { get; set; }
}
public class RegionsOfInterest
{
public int y { get; set; }
public int x { get; set; }
public int height { get; set; }
public int width { get; set; }
}
public class RootObject
{
public string uuid { get; set; }
public string data_type { get; set; }
public long epoch_time { get; set; }
public ProcessingTime processing_time { get; set; }
public int img_height { get; set; }
public int img_width { get; set; }
public List<Result> results { get; set; }
public int credits_monthly_used { get; set; }
public int version { get; set; }
public int credits_monthly_total { get; set; }
public bool error { get; set; }
public List<RegionsOfInterest> regions_of_interest { get; set; }
public int credit_cost { get; set; }
}
}
预期输出应显示一条消息或警告，说明摄像机“无法识别任何车牌”。
答案 0 :(得分：1)
您正在数组中寻找元素0，该元素不存在，这就是为什么会出现错误的原因。
if(vehicresult.results[0].plate.ToString() == "")
您可以通过
解决此问题if(vehicresult.results.Count == 0)