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using HyperBooru.Util;
using Microsoft.EntityFrameworkCore;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text.RegularExpressions;
using Tesseract;
namespace HyperBooru.Services;
public class OcrService : IHostedService {
private readonly TimeSpan ProcessInterval = TimeSpan.FromMinutes(30);
private readonly TimeSpan StartupDelay = TimeSpan.FromSeconds(30);
private readonly Regex SpaceRegex = new(@"[^0-9a-z]+", RegexOptions.Compiled);
private Task? task;
private CancellationTokenSource cts = new();
private Timer timer;
private IServiceScopeFactory scopeFactory;
private ILogger<OcrService> logger;
private IDbContextFactory<HBContext> dbFactory;
public OcrService(
IServiceScopeFactory scopeFactory,
ILogger<OcrService> logger,
IDbContextFactory<HBContext> dbFactory) {
this.scopeFactory = scopeFactory;
this.logger = logger;
this.dbFactory = dbFactory;
timer = new((object? state) => {
if(task is not null && !task.IsCompleted)
return;
cts = new();
task = ProcessAllAsync(cts.Token);
});
}
public Task StartAsync(CancellationToken ct) {
logger.LogInformation("Service starting...");
timer.Change(StartupDelay, ProcessInterval);
return Task.CompletedTask;
}
public Task StopAsync(CancellationToken ct) {
logger.LogInformation("Service stopping...");
timer.Change(Timeout.Infinite, Timeout.Infinite);
cts.Cancel();
return Task.CompletedTask;
}
async Task ProcessAllAsync(CancellationToken ct) {
using var scope = scopeFactory.CreateScope();
var mediaService = scope.ServiceProvider
.GetRequiredService<IMediaService>();
using var db = dbFactory.CreateDbContext();
Guid[] guids = db.Media
.Include(m => m.OcrData)
.Where(m => m.OcrData == null)
.Where(m => m.MimeType.Contains("image/"))
.Select(m => m.Guid)
.ToArray();
db.Dispose();
logger.LogInformation($"Performing OCR pass on {guids.Count()} media items");
var factory = new TaskFactory(new LimitedConcurrencyTaskScheduler());
var tasks = new List<Task>();
var stopwatch = Stopwatch.StartNew();
foreach(var guid in guids)
tasks.Add(factory.StartNew(() => Process(guid, mediaService), ct));
await Task.WhenAll(tasks);
stopwatch.Stop();
var time = stopwatch.Elapsed.ToStringHumanReadable();
logger.LogInformation(
$"Performed OCR pass on {guids.Count()} media items in {time}");
}
private void Process(Guid media, IMediaService mediaService) {
logger.LogDebug($"Performing OCR on media item {media}");
using var db = dbFactory.CreateDbContext();
var m = db.Media
.Include(m => m.OcrData)
.First(m => m.Guid == media);
OcrData o = m.OcrData ?? new();
using var engine = new TesseractEngine("tessdata", "eng", EngineMode.Default);
using var image = Pix.LoadFromFile(mediaService.GetPath(m));
engine.SetVariable("debug_file", NullFile);
o.Timestamp = DateTime.UtcNow;
o.Text = engine.Process(image).GetText().Trim();
o.SearchableText = SpaceRegex.Replace(o.Text.ToLower(), " ").Trim();
m.OcrData = o;
db.SaveChanges();
}
private string NullFile {
get {
if(RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
return "NUL";
else
return "/dev/null";
}
}
}
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