number-plate-ocr-demo

using System;
using System.Linq;
using System.Collections.Generic;
using System.Net.Http;
using System.Text;
using System.Text.Json;
using System.Text.Json.Serialization;
using Polly;
using System.IO;
using System.Net.Http.Headers;

namespace OcrDemo
{
    static class Program
    {
        static void Main(string[] args)
        {
            const string ocrServiceUrl = "https://<YOUR_SERVICE_NAME>.cognitiveservices.azure.com/vision/v3.1/ocr?language=zh-Hant&detectOrientation=true";

            const string imgUrl = "https://thumbs.dreamstime.com/z/netherlands-car-plate-vehicle-registration-number-127253077.jpg";

            var http = HttpClientFactory.Create();
            http.DefaultRequestHeaders.Add("Ocp-Apim-Subscription-Key", "<YOUR_KEY_HERE>");

            var policy = Policy.Handle<HttpRequestException>().WaitAndRetry(new TimeSpan[] {
                TimeSpan.FromSeconds(3)
            });

            const string fixVehicleNumberPath = "r:\\xg-sf-67.jpg";
            var img = File.ReadAllBytes(fixVehicleNumberPath);

            //using var stream = new FileStream(fixVehicleNumberPath, FileMode.Open);
            //var streamContent = new StreamContent(stream);
            //streamContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data");

            policy.Execute(() => {
                //SendRequest(http, ocrServiceUrl, imgUrl);
                //SendRequest(http, ocrServiceUrl, streamContent);
                SendRequest(http, ocrServiceUrl, img);
            });
        }

        private static void SendRequest(HttpClient http, string ocrServiceUrl, string imgUrl)
        {
            var req = new HttpRequestMessage
            {
                Method = HttpMethod.Post,
                RequestUri = new Uri(ocrServiceUrl),
                Content = new StringContent(JsonSerializer.Serialize(new
                {
                    Url = imgUrl
                }), Encoding.UTF8, "application/json")
            };

            var resp = http.SendAsync(req).Result;
            FindWords(resp);
        }

        private static void SendRequest(HttpClient http, string ocrServiceUrl, byte[] img)
        {
            using var byteArrayContent = new ByteArrayContent(img);
            byteArrayContent.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");

            var req = new HttpRequestMessage
            {
                Method = HttpMethod.Post,
                RequestUri = new Uri(ocrServiceUrl),
                Content = byteArrayContent
            };

            var resp = http.SendAsync(req).Result;
            FindWords(resp);
        }

        private static void SendRequest(HttpClient http, string ocrServiceUrl, StreamContent imgStream)
        {
            var req = new HttpRequestMessage
            {
                Method = HttpMethod.Post,
                RequestUri = new Uri(ocrServiceUrl),
                Content = new MultipartFormDataContent { imgStream }
            };

            var resp = http.SendAsync(req).Result;
            FindWords(resp);
        }

        private static void FindWords(HttpResponseMessage resp)
        {
            if (resp.IsSuccessStatusCode)
            {
                var ret = JsonSerializer.Deserialize<DetectedResult>(resp.Content.ReadAsStringAsync().Result);
                if (ret is not null)
                {
                    foreach (var region in ret.Regions)
                    {
                        foreach (var line in region.Lines)
                        {
                            var wordsInLine = new StringBuilder();
                            _ = line.Words.Where(x => !string.IsNullOrEmpty(x.Text))
                                            .Aggregate(wordsInLine, (result, item) => result.Append(item.Text));
                            Console.WriteLine($"{wordsInLine}");
                        }
                    }
                }
            }
            else
            {
                Console.WriteLine($"{resp.ReasonPhrase}\n{resp.Content.ReadAsStringAsync().Result}");
            }
        }
    }

    public record DetectedResult
    {
        [JsonPropertyName("language")]
        public string Language { get; init; }
        [JsonPropertyName("textAngle")]
        public float TextAngle { get; init; }
        [JsonPropertyName("orientation")]
        public string Orientation { get; init; }
        [JsonPropertyName("regions")]
        public IEnumerable<Region> Regions { get; init; }
    }

    public record Region
    {
        [JsonPropertyName("boundingBox")]
        public string BoundingBox { get; init; }
        [JsonPropertyName("lines")]
        public IEnumerable<Line> Lines { get; init; }
    }

    public record Line
    {
        [JsonPropertyName("boundingBox")]
        public string BoundingBox { get; init; }
        [JsonPropertyName("words")]
        public IEnumerable<Word> Words { get; init; }
    }

    public record Word
    {
        [JsonPropertyName("boundingBox")]
        public string BoundingBox { get; init; }
        [JsonPropertyName("text")]
        public string Text { get; init; }
    }


}