DLL image text extractor

I'm looking for a DLL code library for my application to extract text from image files (jpg, gif, bmp,TIF etc).? An external program can call the text extraction function in the DLL with the selected image file name, and? the text string in the image will be returned to the? program. Source codes are required. I had a programmer to develop this code for me a while ago. However, the program cannot parse some? images.? You can make changes on? this program? or use your own. The program language needs to be in C#.? I can use Office MODI? if required by your program.