How to extract text from image without using OCR tool ?

https://geekflare.com/convert-image-to-text/

You have to use an OCR tool to read text from images. Spire.OCR can help you achieve this task:

https://www.e-iceblue.com/Tutorials/Spire.OCR/Quick-Start-for-.NET-Core/How-to-use-Spire.OCR-for-.NET-in-.NET-Core-Applications.html

https://www.c-sharpcorner.com/article/ocr-using-tesseract-in-C-Sharp/

If the input files you are using are already searchable in nature, such as PDF or DOCX, you can use the LEADTOOLS GetText() method to get the text without running OCR. In cases outside of this, this will run OCR which would be required to extract the text. Here is an example that you can build on:

using (var document = DocumentFactory.LoadFromFile(@“C:\input\1.pdf”, new LoadDocumentOptions())) 
{ 
    var ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD); 
    var rasterCodecs = new RasterCodecs(); 
    var documentWriter = new DocumentWriter(); 
    ocrEngine.Startup(rasterCodecs, documentWriter, null, LEAD_VARS.OcrLEADRuntimeDir); 

    document.Text.OcrEngine = ocrEngine; 

    // get text  
    var page = document.Pages[0]; 
    var pageText = page.GetText(); 
    if (pageText != null) 
    { 
        pageText.BuildText(); 
        var text = pageText.Text; 

        Console.WriteLine(text); 
    }
}

https://www.leadtools.com/help/sdk/v22/dh/dox/documentpage-gettext().html
https://www.leadtools.com/help/sdk/v22/tutorials/dotnet-console-parse-the-text-of-a-document.html