使用IronOCR處理CAPTCHA

Curtis Chau

Updated: 2026年6月29日

IronOCR會識別captcha程式碼嗎？

這是可能的，但不能保證。

大多數CAPTCHA生成器故意設計來愚弄OCR軟體，有些甚至使用類似Tesseract的"不能被OCR軟體讀取"作為單元測試。

Captcha程式碼本質上對OCR引擎來說非常難以識別。解析度非常低，每個字元的角度和間隙都與其他字元不同，並且包括可變的背景噪音。

去除背景噪音的灰階圖像比彩色圖像更成功，但仍然具有挑戰性：

OcrInput.DeNoise() or OcrInput.DeepCleanBackgroundNoise() Filter
OcrInput.ToGrayScale() Filter

以下是嘗試去除噪音並將CAPTCHA圖像轉換為灰階以改善OCR結果的C#範例程式碼：

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

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