OcrService.cs

using System.Net.Http.Headers;
using IdApp.Cv;
using Waher.Content;
using Waher.Runtime.Inventory;
 
namespace NeuroAccessMaui.Services.Ocr
{
    [Singleton]
    public class OcrService : IOcrService
    {
        public OcrService()
            : base()
        {
        }
 
        public async Task<string[]> ProcessImage(IMatrix Image, string Language, PageSegmentationMode? PageSegmentationMode)
        {
            byte[] Png = Bitmaps.EncodeAsPng(Image);
            string? Token = await ServiceRef.XmppService.GetApiToken(60);
 
            Uri Uri = new("https://" + ServiceRef.TagProfile.Domain + "/Tesseract/Api");
            using HttpClient HttpClient = new();
            using HttpRequestMessage Request = new()
            {
                RequestUri = Uri,
                Method = HttpMethod.Post,
                Content = new ByteArrayContent(Png)
            };
 
            Request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("image/png");
            Request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", Token);
 
            if (!string.IsNullOrEmpty(Language))
                Request.Headers.Add("X-LANGUAGE", Language);
 
            if (PageSegmentationMode.HasValue)
                Request.Headers.Add("X-PSM", PageSegmentationMode.Value.ToString());
 
            HttpResponseMessage Response = await HttpClient.SendAsync(Request);
            Response.EnsureSuccessStatusCode();
 
            byte[] Bin = await Response.Content.ReadAsByteArrayAsync();
            string? ContentType = Response.Content.Headers.ContentType?.ToString();
            object Obj = await InternetContent.DecodeAsync(ContentType, Bin, Uri);
 
            if (Obj is not string Text)
                throw new Exception("Unexpected response.");
 
            if (string.IsNullOrEmpty(Text))
                return [];
            else
                return Text.Split(CommonTypes.CRLF, StringSplitOptions.RemoveEmptyEntries);
        }
 
    }
}