You can use Boxoft Screen OCR to capture sentences from image. it enables you capture anywhere on your screen, recognize every character then save as TXT file, including placement that you can't copy with mouse, such as PDF, dialog box and error message, etc.
Follow easy steps below:
Launch it by double click its desktop icon;
Select a kind of language which you want to extract;
Set a hotkey to later cut anywhere from image out conveniently;
Click "Capture" or use "Hotkey" to select words from image;
Choose an area with mouse;
Click "OCR", then edit text in the popup edit box;