使用 IronOCR 處理驗證碼

Curtis Chau

更新:2025年6月9日

Translated

View the article in English

IronOCR能讀取驗證碼嗎？

這有可能，但不能保證。

大多數 CAPTCHA 產生器都經過精心設計，旨在欺騙 OCR 軟體，有些甚至使用"無法被 OCR 軟體（如 Tesseract）讀取"作為單元測試。

根據定義，驗證碼對於OCR引擎來說非常難以讀取。解析度非常低，每個字元都經過精心安排，與其他字元的角度和間距各不相同，並且還加入了變化的背景噪音。

移除背景雜訊後的灰階影像比彩色影像更容易處理，但仍具有挑戰性：

OcrInput.DeNoise()或OcrInput.DeepCleanBackgroundNoise()濾波器
OcrInput.ToGrayScale()過濾器

以下是 C# 程式碼範例，嘗試移除雜訊並將 CAPTCHA 影像轉換為灰階影像，以提高 OCR 結果：

using IronOcr;

class CaptchaReader
{
    static void Main(string[] args)
    {
        // Initialize the IronOCR engine
        var Ocr = new IronTesseract();

        // Create an OCR input object
        var Input = new OcrInput("captcha-image.jpg");

        // Apply noise reduction to improve OCR accuracy
        // This removes background noise while preserving text
        Input.DeNoise();

        // Optionally apply a deep clean for more aggressive noise removal
        Input.DeepCleanBackgroundNoise();

        // Convert the image to grayscale 
        // OCR works better on grayscale images compared to colored ones
        Input.ToGrayScale();

        // Perform OCR to extract text from the image
        var Result = Ocr.Read(Input);

        // Output the recognized text to the console
        Console.WriteLine(Result.Text);
    }
}

using IronOcr;

class CaptchaReader
{
    static void Main(string[] args)
    {
        // Initialize the IronOCR engine
        var Ocr = new IronTesseract();

        // Create an OCR input object
        var Input = new OcrInput("captcha-image.jpg");

        // Apply noise reduction to improve OCR accuracy
        // This removes background noise while preserving text
        Input.DeNoise();

        // Optionally apply a deep clean for more aggressive noise removal
        Input.DeepCleanBackgroundNoise();

        // Convert the image to grayscale 
        // OCR works better on grayscale images compared to colored ones
        Input.ToGrayScale();

        // Perform OCR to extract text from the image
        var Result = Ocr.Read(Input);

        // Output the recognized text to the console
        Console.WriteLine(Result.Text);
    }
}

Imports IronOcr

Friend Class CaptchaReader
	Shared Sub Main(ByVal args() As String)
		' Initialize the IronOCR engine
		Dim Ocr = New IronTesseract()

		' Create an OCR input object
		Dim Input = New OcrInput("captcha-image.jpg")

		' Apply noise reduction to improve OCR accuracy
		' This removes background noise while preserving text
		Input.DeNoise()

		' Optionally apply a deep clean for more aggressive noise removal
		Input.DeepCleanBackgroundNoise()

		' Convert the image to grayscale 
		' OCR works better on grayscale images compared to colored ones
		Input.ToGrayScale()

		' Perform OCR to extract text from the image
		Dim Result = Ocr.Read(Input)

		' Output the recognized text to the console
		Console.WriteLine(Result.Text)
	End Sub
End Class

$vbLabelText $csharpLabel