What is TesseractOCR
It is a .NET wrapper for Tesseract 5.3.1 that is originally copied from Charles Weld (https://github.com/charlesw/tesseract) and modified for my own needs
How to use
You need trained data in tessdata by language You can get them at https://github.com/tesseract-ocr/tessdata or https://github.com/tesseract-ocr/tessdata_fast
Microsoft Visual C++ runtimes
The DLL's Tesseract53.dll (and exe) and leptonica-1.83.0.dll are compiled with Visual Studio 2022 you need these C++ runtimes for it on your computer
- X86: https://aka.ms/vs/17/release/vc_redist.x86.exe
- X64: https://aka.ms/vs/17/release/vc_redist.x64.exe
OCR a page
using var engine = new Engine(@"./tessdata", Language.English, EngineMode.Default);
using var img = TesseractOCR.Pix.Image.LoadFromFile(testImagePath);
using var page = engine.Process(img);
Console.WriteLine("Mean confidence: {0}", page.MeanConfidence);
Console.WriteLine("Text: \r\n{0}", page.Text);Iterate through the layout of a page
using var engine = new Engine(@"./tessdata", Language.English, EngineMode.Default);
using var img = Pix.Image.LoadFromFile(testImagePath);
using var page = engine.Process(img);
foreach (var block in page.Layout)
{
result.AppendLine($"Block confidence: {block.Confidence}");
if (block.BoundingBox != null)
{
var boundingBox = block.BoundingBox.Value;
result.AppendLine($"Block bounding box X1 '{boundingBox.X1}', Y1 '{boundingBox.Y2}', X2 " +
$"'{boundingBox.X2}', Y2 '{boundingBox.Y2}', width '{boundingBox.Width}', height '{boundingBox.Height}'");
}
result.AppendLine($"Block text: {block.Text}");
foreach (var paragraph in block.Paragraphs)
{
result.AppendLine($"Paragraph confidence: {paragraph.Confidence}");
if (paragraph.BoundingBox != null)
{
var boundingBox = paragraph.BoundingBox.Value;
result.AppendLine($"Paragraph bounding box X1 '{boundingBox.X1}', Y1 '{boundingBox.Y2}', X2 " +
$"'{boundingBox.X2}', Y2 '{boundingBox.Y2}', width '{boundingBox.Width}', height '{boundingBox.Height}'");
}
var info = paragraph.Info;
result.AppendLine($"Paragraph info justification: {info.Justification}");
result.AppendLine($"Paragraph info is list item: {info.IsListItem}");
result.AppendLine($"Paragraph info is crown: {info.IsCrown}");
result.AppendLine($"Paragraph info first line ident: {info.FirstLineIdent}");
result.AppendLine($"Paragraph text: {paragraph.Text}");
foreach (var textLine in paragraph.TextLines)
{
if (textLine.BoundingBox != null)
{
var boundingBox = textLine.BoundingBox.Value;
result.AppendLine($"Text line bounding box X1 '{boundingBox.X1}', Y1 '{boundingBox.Y2}', X2 " +
$"'{boundingBox.X2}', Y2 '{boundingBox.Y2}', width '{boundingBox.Width}', height '{boundingBox.Height}'");
}
result.AppendLine($"Text line confidence: {textLine.Confidence}");
result.AppendLine($"Text line text: {textLine.Text}");
foreach (var word in textLine.Words)
{
result.AppendLine($"Word confidence: {word.Confidence}");
if (word.BoundingBox != null)
{
var boundingBox = word.BoundingBox.Value;
result.AppendLine($"Word bounding box X1 '{boundingBox.X1}', Y1 '{boundingBox.Y2}', X2 " +
$"'{boundingBox.X2}', Y2 '{boundingBox.Y2}', width '{boundingBox.Width}', height '{boundingBox.Height}'");
}
result.AppendLine($"Word is from dictionary: {word.IsFromDictionary}");
result.AppendLine($"Word is numeric: {word.IsNumeric}");
result.AppendLine($"Word language: {word.Language}");
result.AppendLine($"Word text: {word.Text}");
foreach (var symbol in word.Symbols)
{
result.AppendLine($"Symbol confidence: {symbol.Confidence}");
if (symbol.BoundingBox != null)
{
var boundingBox = symbol.BoundingBox.Value;
result.AppendLine($"Symbol bounding box X1 '{boundingBox.X1}', Y1 '{boundingBox.Y2}', X2 " +
$"'{boundingBox.X2}', Y2 '{boundingBox.Y2}', width '{boundingBox.Width}', height '{boundingBox.Height}'");
}
result.AppendLine($"Symbol is superscript: {symbol.IsSuperscript}");
result.AppendLine($"Symbol is dropcap: {symbol.IsDropcap}");
result.AppendLine($"Symbol text: {symbol.Text}");
}
}
}
}
}For more examples see https://github.com/Sicos1977/TesseractOCR/wiki/examples.md
Supported input formats
Tesseract uses the Leptonica library to read images with one of these formats:
- PNG - requires libpng, libz
- JPEG - requires libjpeg / libjpeg-turbo
- TIFF - requires libtiff, libz
- JPEG 2000 - requires libopenjp2
- GIF - requires libgif (giflib)
- WebP (including animated WebP) - requires libwebp
- BMP - no library required* = PNM - no library required*
- Except Leptonica
I have dropped support for the Windows.Drawing.Image namespace since this only works good on Windows and not on other systems. You should be fine with Leptonica
Logging
TesseractOCR uses the Microsoft ILogger interface (https://docs.microsoft.com/en-us/dotnet/api/microsoft.extensions.logging.ilogger?view=dotnet-plat-ext-5.0). You can use any logging library that uses this interface.
TesseractOCR has some build in loggers that can be found in the TesseractOCR.Logger namespace.
For example
var logger = !string.IsNullOrWhiteSpace(<some logfile>)
? new TesseractOCR.Loggers.Stream(File.OpenWrite(<some logfile>))
: new TesseractOCR.Loggers.Console();Installing via NuGet
The easiest way to install TesseractOCR is via NuGet.
In Visual Studio's Package Manager Console, simply enter the following command:
Install-Package TesseractOCR
License Information
- Copyright 2012-2019 Charles Weld (https://github.com/charlesw)
- Copyright 2021-2023 Kees van Spelde
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.