Testmate uses Tesseract to provide OCR support. Tesseract is an optical character recognition engine for various operating systems. It support a lot of languages, complete list can be found here.
To use Tesseract, all you need to do is download tessdata library.
Use the below code to OCR the image:
'Read text from img.png using "eng" language from tessdata
sText = ocr.ReadText("C:\Users\...\Desktop\img.png","C:\Users\...\Desktop\tessdata","eng")