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SeasonEngine/
SeasonOCR

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SeasonOCR

SeasonOCR for EasyOCR Models is a .NET OCR library for ONNX models converted from the EasyOCR Python project.

The initial public release focuses on a clean CPU-only API:

caller-managed long-lived InferenceSession instances
no complex model path binding inside the library
EasyOCR-style box detection, recognition, and paragraph grouping
optional annotated output image and optional debug report

Project Links

GitHub: SeasonRealms/SeasonOCR
Models: SeasonEngine/SeasonOCR on Hugging Face
ONNX export workflow: export-easyocr-onnx.yml

If you prefer to build the ONNX models yourself, clone the repository and run the workflow logic locally.

Origin

The OCR pipeline is translated and adapted from EasyOCR.
The intended model inputs are ONNX files converted from EasyOCR Python models.
Files translated from EasyOCR Python sources include source attribution and an explicit modification notice in the file header.

Features

EasyOCR-style CRAFT post-processing
CRNN / CTC recognition
Beam search by default
Optional dictionary-aware word beam search
Perspective rectification for rotated text regions
Optional rotation TTA, disabled by default
Structured OCR output with boxes, paragraphs, and summary text
Optional JPEG annotated image in box-only preview style
Optional debug report controlled by SeasonOcr.EnableDebugOutput
Automatic recognizer language discovery from ONNX metadata
Embedded dictionary loading from recognizer ONNX metadata

Install

dotnet add package SeasonOCR

Quick Start

csharp

using System.Text;
using Microsoft.ML.OnnxRuntime;
using SeasonOCR;
using StbImageSharp;

SeasonOcr.EnableDebugOutput = true;

var detectorBytes = File.ReadAllBytes(@"craft_mlt_25k.onnx");
using var detectorSession = new InferenceSession(detectorBytes);

var recognizerBytes = File.ReadAllBytes(@"recognizer_ch_sim.onnx");
using var recognizerSession = new InferenceSession(recognizerBytes);

using var stream = File.OpenRead(@"chinese.jpg");
var image = ImageResult.FromStream(stream, ColorComponents.RedGreenBlue);

var result = SeasonOcr.Detect(
    detectorSession,
    recognizerSession,
    image,
    createAnnotatedImage: true);

Console.WriteLine(result.Summary);

foreach (var paragraph in result.Paragraphs)
{
    Console.WriteLine($"{paragraph.Confidence:P0}: {paragraph.Text}");
}

if (result.AnnotatedImage.Length > 0)
    File.WriteAllBytes(@"output.jpg", result.AnnotatedImage);

if (!string.IsNullOrWhiteSpace(result.DebugReport))
    File.WriteAllText(@"output.debug.txt", result.DebugReport, Encoding.UTF8);

Why This API

This initial API is intentionally session-based:

You create and reuse InferenceSession instances yourself.
The library only consumes the prepared detector session, recognizer session, and decoded image.
This avoids hidden path resolution rules inside the OCR call path.
It also fits engine-style hosts and service applications that want explicit control over model lifetime.

For the first release, the recommended runtime target is CPU execution.

API Notes

SeasonOcr.Detect(...) current signature:

csharp

public static SeasonOcrResult Detect(
    InferenceSession detectorSession,
    InferenceSession recognizerSession,
    ImageResult imageResult,
    bool enableWordBeamSearch = false,
    bool allowRotatedRecognition = false,
    bool createAnnotatedImage = false,
    int beamWidth = 5,
    string? dictionary = null)

Parameter behavior:

enableWordBeamSearch: enables dictionary-aware decoding when usable dictionary data is available
allowRotatedRecognition: enables rotation TTA for recognition; default is false
createAnnotatedImage: when true, result.AnnotatedImage contains a JPEG like output.jpg
beamWidth: beam width used by beam search
dictionary: optional in-memory dictionary content; when omitted, embedded model dictionaries are used if present

Multilingual support

"en", "recognizer_en.onnx", "English"
"latin", "recognizer_latin.onnx", "Latina"
"zh-CN", "recognizer_ch_sim.onnx", "中文简体"
"zh-TW", "recognizer_ch_tra.onnx", "中文繁體"
"ja", "recognizer_ja.onnx", "日本語"
"ko", "recognizer_ko.onnx", "한국어"
"th", "recognizer_th.onnx", "ไทย"
"ta", "recognizer_ta.onnx", "தமிழ்"
"te", "recognizer_te.onnx", "తెలుగు"
"kn", "recognizer_kn.onnx", "ಕನ್ನಡ"
"ar", "recognizer_ar.onnx", "العربية"
"ru", "recognizer_ru.onnx", "Русский"
"hi", "recognizer_hi.onnx", "हिन्दी"
"bn", "recognizer_bn.onnx", "বাংলা"

Debug Output

Enable debug output before calling the OCR API:

SeasonOcr.EnableDebugOutput = true;

When enabled:

internal debug logging is emitted through Debug.WriteLine(...)
SeasonOcrResult.DebugReport is populated
per-box debug information can be inspected through SeasonOcrResult.DebugBoxes

When disabled:

debug logging is skipped
DebugReport stays empty unless explicitly produced by the current flow

Result Contents

SeasonOcrResult can contain:

Summary: human-readable OCR summary
Boxes: recognized text boxes kept in the final result
Paragraphs: grouped paragraph output
AnnotatedImage: JPEG bytes for the box-only preview image
DebugBoxes: per-box debug data
DebugReport: plain-text debug report suitable for saving as output.debug.txt

Models

Recommended model sources:

Download ready-made ONNX models from Hugging Face
Or generate them yourself from the repository workflow: export-easyocr-onnx.yml

Recognizer metadata support:

SeasonOCR reads embedded recognizer charset metadata when available
SeasonOCR reads recognizer lang_list metadata when available
Embedded dictionaries such as dict_<lang> are used automatically for word beam search

Output Image

When createAnnotatedImage is true, the library generates a JPEG preview similar to the official EasyOCR examples:

green detection boxes only
no confidence text overlay
suitable for saving directly as output.jpg

Status

Current release scope:

CPU-first
stable public OCR API
session-based integration for application hosts

Planned for later:

engine-oriented runtime helpers
GPU provider options
additional provider-specific optimization layers

License

The project is distributed under Apache License 2.0.
See LICENSE and THIRD_PARTY_NOTICES.md for attribution and third-party details.

SeasonEngine/SeasonOCR