Paddle OCR vs Tesseract：詳細的 OCR 比較

// Five packages required before this compiles:
// dotnet add package Sdcb.PaddleOCR
// dotnet add package Sdcb.PaddleOCR.Models.Online
// dotnet add package Sdcb.PaddleInference.runtime.win64.mkl
// dotnet add package OpenCvSharp4
// dotnet add package OpenCvSharp4.runtime.win

using Sdcb.PaddleOCR;
using Sdcb.PaddleOCR.Models.Online;
using OpenCvSharp;

// Async download from Baidu servers — blocks first run for 10-30 seconds
FullOcrModel models = await OnlineFullModels.ChineseV4.DownloadAsync();

// PaddleOcrAll bundles detection, classification, and recognition
using PaddleOcrAll ocr = new PaddleOcrAll(models)
{
    AllowRotateDetection = true,
    Enable180Classification = true
};

// OpenCV required — no file path shortcut
using Mat mat = Cv2.ImRead("document.png");

if (mat.Empty())
{
    throw new FileNotFoundException("Could not load image");
}

// Three neural networks fire in sequence
PaddleOcrResult result = ocr.Run(mat);

Console.WriteLine(result.Text);

Imports Sdcb.PaddleOCR
Imports Sdcb.PaddleOCR.Models.Online
Imports OpenCvSharp

' Five packages required before this compiles:
' dotnet add package Sdcb.PaddleOCR
' dotnet add package Sdcb.PaddleOCR.Models.Online
' dotnet add package Sdcb.PaddleInference.runtime.win64.mkl
' dotnet add package OpenCvSharp4
' dotnet add package OpenCvSharp4.runtime.win

' Async download from Baidu servers — blocks first run for 10-30 seconds
Dim models As FullOcrModel = Await OnlineFullModels.ChineseV4.DownloadAsync()

' PaddleOcrAll bundles detection, classification, and recognition
Using ocr As New PaddleOcrAll(models) With {
    .AllowRotateDetection = True,
    .Enable180Classification = True
}

    ' OpenCV required — no file path shortcut
    Using mat As Mat = Cv2.ImRead("document.png")

        If mat.Empty() Then
            Throw New FileNotFoundException("Could not load image")
        End If

        ' Three neural networks fire in sequence
        Dim result As PaddleOcrResult = ocr.Run(mat)

        Console.WriteLine(result.Text)
    End Using
End Using

// Chinese model: highest accuracy for CJK documents
FullOcrModel models = await OnlineFullModels.ChineseV4.DownloadAsync();

using PaddleOcrAll ocr = new PaddleOcrAll(models)
{
    AllowRotateDetection = true,
    Enable180Classification = true
};

using Mat mat = Cv2.ImRead("chinese-invoice.png");
PaddleOcrResult result = ocr.Run(mat);

// Filter low-confidence regions for cleaner output
var highConfidence = result.Regions
    .Where(r => r.Score >= 0.8)
    .OrderBy(r => r.Rect.Center.Y)
    .ThenBy(r => r.Rect.Center.X);

foreach (var region in highConfidence)
{
    Console.WriteLine($"{region.Text} ({region.Score:P0})");
}

Imports System
Imports System.Linq
Imports OpenCvSharp

' Chinese model: highest accuracy for CJK documents
Dim models As FullOcrModel = Await OnlineFullModels.ChineseV4.DownloadAsync()

Using ocr As New PaddleOcrAll(models) With {
    .AllowRotateDetection = True,
    .Enable180Classification = True
}

    Using mat As Mat = Cv2.ImRead("chinese-invoice.png")
        Dim result As PaddleOcrResult = ocr.Run(mat)

        ' Filter low-confidence regions for cleaner output
        Dim highConfidence = result.Regions _
            .Where(Function(r) r.Score >= 0.8) _
            .OrderBy(Function(r) r.Rect.Center.Y) _
            .ThenBy(Function(r) r.Rect.Center.X)

        For Each region In highConfidence
            Console.WriteLine($"{region.Text} ({region.Score:P0})")
        Next
    End Using
End Using

// dotnet add package IronOcr.Languages.ChineseSimplified

using IronOcr;

var ocr = new IronTesseract();
ocr.Language = OcrLanguage.ChineseSimplified;

using var input = new OcrInput();
input.LoadImage("chinese-invoice.png");

// Preprocessing handles rotation, noise, and contrast automatically
input.Deskew();
input.DeNoise();

var result = ocr.Read(input);

// Word-level results with coordinates
foreach (var word in result.Words)
{
    Console.WriteLine($"{word.Text} at ({word.X},{word.Y}) — {word.Confidence}%");
}

Imports IronOcr

' dotnet add package IronOcr.Languages.ChineseSimplified

Dim ocr As New IronTesseract()
ocr.Language = OcrLanguage.ChineseSimplified

Using input As New OcrInput()
    input.LoadImage("chinese-invoice.png")

    ' Preprocessing handles rotation, noise, and contrast automatically
    input.Deskew()
    input.DeNoise()

    Dim result = ocr.Read(input)

    ' Word-level results with coordinates
    For Each word In result.Words
        Console.WriteLine($"{word.Text} at ({word.X},{word.Y}) — {word.Confidence}%")
    Next
End Using

// Option A: Online download — simplest, but requires Baidu server access
// This runs on application startup; first run blocks for 10-30 seconds
FullOcrModel onlineModels = await OnlineFullModels.ChineseV4.DownloadAsync();

// Option B: Pre-downloaded local models — for air-gapped or compliance environments
// Developer must manually download and maintain three directories:
//   models/ch_PP-OCRv4_det_infer/
//   models/ch_ppocr_mobile_v2.0_cls_infer/
//   models/ch_PP-OCRv4_rec_infer/
FullOcrModel localModels = new FullOcrModel(
    LocalDetectionModel.FromDirectory("models/ch_PP-OCRv4_det_infer"),
    LocalClassificationModel.FromDirectory("models/ch_ppocr_mobile_v2.0_cls_infer"),
    LocalRecognitionModel.FromDirectory("models/ch_PP-OCRv4_rec_infer")
);

// Option C: Embedded model package — adds 100MB to NuGet restore, simplest deployment
// dotnet add package Sdcb.PaddleOCR.Models.LocalV4

// Japanese and Korean require separate model downloads:
FullOcrModel japaneseModels = await OnlineFullModels.JapanV4.DownloadAsync();
FullOcrModel koreanModels = await OnlineFullModels.KoreanV4.DownloadAsync();

// dotnet add package IronOcr
// dotnet add package IronOcr.Languages.ChineseSimplified
// dotnet add package IronOcr.Languages.Japanese

using IronOcr;

//不是async initialization, no model path, no version matching
var ocr = new IronTesseract();
ocr.Language = OcrLanguage.ChineseSimplified;
ocr.AddSecondaryLanguage(OcrLanguage.Japanese);

using var input = new OcrInput();
input.LoadImage("mixed-cjk-document.png");

var result = ocr.Read(input);
Console.WriteLine(result.Text);

Imports IronOcr

' dotnet add package IronOcr
' dotnet add package IronOcr.Languages.ChineseSimplified
' dotnet add package IronOcr.Languages.Japanese

'不是async initialization, no model path, no version matching
Dim ocr As New IronTesseract()
ocr.Language = OcrLanguage.ChineseSimplified
ocr.AddSecondaryLanguage(OcrLanguage.Japanese)

Using input As New OcrInput()
    input.LoadImage("mixed-cjk-document.png")

    Dim result = ocr.Read(input)
    Console.WriteLine(result.Text)
End Using

// Prerequisites (must be installed before this compiles correctly):
// 1. NVIDIA GPU with CUDA capability 3.5+
// 2. NVIDIA Driver 452.39+ (Windows) / 450.80.02+ (Linux)
// 3. CUDA Toolkit 11.8 — exact version, not 12.x
// 4. cuDNN 8.6.0+ for CUDA 11.x
// 5. dotnet add package Sdcb.PaddleInference.runtime.win64.cuda118

using Sdcb.PaddleOCR;
using Sdcb.PaddleOCR.Models.Online;
using Sdcb.PaddleInference;
using OpenCvSharp;

FullOcrModel models = await OnlineFullModels.ChineseV4.DownloadAsync();

// GPU device 0, 1000MB GPU memory pool
using PaddleOcrAll ocr = new PaddleOcrAll(models, PaddleDevice.Gpu(deviceId: 0))
{
    AllowRotateDetection = true,
    Enable180Classification = true
};

using Mat mat = Cv2.ImRead(imagePath);
PaddleOcrResult result = ocr.Run(mat);

Imports Sdcb.PaddleOCR
Imports Sdcb.PaddleOCR.Models.Online
Imports Sdcb.PaddleInference
Imports OpenCvSharp

' Prerequisites (must be installed before this compiles correctly):
' 1. NVIDIA GPU with CUDA capability 3.5+
' 2. NVIDIA Driver 452.39+ (Windows) / 450.80.02+ (Linux)
' 3. CUDA Toolkit 11.8 — exact version, not 12.x
' 4. cuDNN 8.6.0+ for CUDA 11.x
' 5. dotnet add package Sdcb.PaddleInference.runtime.win64.cuda118

Dim models As FullOcrModel = Await OnlineFullModels.ChineseV4.DownloadAsync()

' GPU device 0, 1000MB GPU memory pool
Using ocr As New PaddleOcrAll(models, PaddleDevice.Gpu(deviceId:=0)) With {
    .AllowRotateDetection = True,
    .Enable180Classification = True
}

    Using mat As Mat = Cv2.ImRead(imagePath)
        Dim result As PaddleOcrResult = ocr.Run(mat)
    End Using

End Using

using IronOcr;

//不是GPU setup, no CUDA, no driver checks
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY";

var ocr = new IronTesseract();

// Preprocessing built-in — improves accuracy on poor scans without extra code
using var input = new OcrInput();
input.LoadImage("document.png");
input.Deskew();
input.DeNoise();
input.EnhanceResolution(300);

var result = ocr.Read(input);
Console.WriteLine($"Confidence: {result.Confidence}%");

Imports IronOcr

' 不是GPU setup, no CUDA, no driver checks
IronOcr.License.LicenseKey = "YOUR-LICENSE-KEY"

Dim ocr As New IronTesseract()

' Preprocessing built-in — improves accuracy on poor scans without extra code
Using input As New OcrInput()
    input.LoadImage("document.png")
    input.Deskew()
    input.DeNoise()
    input.EnhanceResolution(300)

    Dim result = ocr.Read(input)
    Console.WriteLine($"Confidence: {result.Confidence}%")
End Using

// Requires additional package: PdfiumViewer or similar
using Sdcb.PaddleOCR;
using Sdcb.PaddleOCR.Models.Online;
using OpenCvSharp;
using PdfiumViewer;
using System.Drawing.Imaging;
using System.Text;

FullOcrModel models = await OnlineFullModels.ChineseV4.DownloadAsync();
using PaddleOcrAll ocr = new PaddleOcrAll(models);

var results = new StringBuilder();

//手動PDF-to-image conversion, page by page
using PdfDocument pdf = PdfDocument.Load("document.pdf");

for (int i = 0; i < pdf.PageCount; i++)
{
    // Render page to bitmap — 200 DPI
    using var pageImage = pdf.Render(i, 200, 200, PdfRenderFlags.CorrectFromDpi);

    // Save to temp file — OpenCvSharp cannot read from memory easily
    string tempPath = Path.GetTempFileName() + ".png";
    pageImage.Save(tempPath, ImageFormat.Png);

    try
    {
        using Mat mat = Cv2.ImRead(tempPath);
        var result = ocr.Run(mat);
        results.AppendLine($"--- Page {i + 1} ---");
        results.AppendLine(result.Text);
    }
    finally
    {
        File.Delete(tempPath);  // Must clean up temp files
    }
}

return results.ToString();

Imports Sdcb.PaddleOCR
Imports Sdcb.PaddleOCR.Models.Online
Imports OpenCvSharp
Imports PdfiumViewer
Imports System.Drawing.Imaging
Imports System.Text

Public Module PdfToTextConverter
    Public Async Function ConvertPdfToText() As Task(Of String)
        Dim models As FullOcrModel = Await OnlineFullModels.ChineseV4.DownloadAsync()
        Using ocr As New PaddleOcrAll(models)
            Dim results As New StringBuilder()

            ' 手動PDF-to-image conversion, page by page
            Using pdf As PdfDocument = PdfDocument.Load("document.pdf")
                For i As Integer = 0 To pdf.PageCount - 1
                    ' Render page to bitmap — 200 DPI
                    Using pageImage = pdf.Render(i, 200, 200, PdfRenderFlags.CorrectFromDpi)
                        ' Save to temp file — OpenCvSharp cannot read from memory easily
                        Dim tempPath As String = Path.GetTempFileName() & ".png"
                        pageImage.Save(tempPath, ImageFormat.Png)

                        Try
                            Using mat As Mat = Cv2.ImRead(tempPath)
                                Dim result = ocr.Run(mat)
                                results.AppendLine($"--- Page {i + 1} ---")
                                results.AppendLine(result.Text)
                            End Using
                        Finally
                            File.Delete(tempPath) ' Must clean up temp files
                        End Try
                    End Using
                Next
            End Using

            Return results.ToString()
        End Using
    End Function
End Module

using IronOcr;

var ocr = new IronTesseract();

//本地PDF輸入— no external library needed
using var input = new OcrInput();
input.LoadPdf("document.pdf");

var result = ocr.Read(input);

// Per-page access available if needed
foreach (var page in result.Pages)
{
    Console.WriteLine($"Page {page.PageNumber}: {page.Text.Length} chars");
}

// Produce a searchable PDF in one additional line
result.SaveAsSearchablePdf("searchable-output.pdf");

Imports IronOcr

Dim ocr As New IronTesseract()

'本地PDF輸入— no external library needed
Using input As New OcrInput()
    input.LoadPdf("document.pdf")

    Dim result = ocr.Read(input)

    ' Per-page access available if needed
    For Each page In result.Pages
        Console.WriteLine($"Page {page.PageNumber}: {page.Text.Length} chars")
    Next

    ' Produce a searchable PDF in one additional line
    result.SaveAsSearchablePdf("searchable-output.pdf")
End Using

using IronOcr;

var ocr = new IronTesseract();

using var input = new OcrInput();
input.LoadImage("low-quality-scan.png");

// These filters recover the accuracy that PaddleOCR provided automatically
// on noisy or skewed inputs
input.Deskew();
input.DeNoise();
input.Contrast();
input.Binarize();
input.EnhanceResolution(300);

var result = ocr.Read(input);

Imports IronOcr

Dim ocr As New IronTesseract()

Using input As New OcrInput()
    input.LoadImage("low-quality-scan.png")

    ' These filters recover the accuracy that PaddleOCR provided automatically
    ' on noisy or skewed inputs
    input.Deskew()
    input.DeNoise()
    input.Contrast()
    input.Binarize()
    input.EnhanceResolution(300)

    Dim result = ocr.Read(input)
End Using