C# Class to Manipulate Image files

I need a C# Class, which will be integrated in a program that we already have. The objetive of this class is to paint in black a square part of a given image and return the resulting image. The parameters to be sent is: Image, upper left corner coordinates, lower right corner coordinates of the area to be painter. The result should be the image with that black box replacing the previous content. I have attached three images. The objective is to remove the numbers (TAGS) that have been artificially introduced to the image. Please, fell free to ask any questions. Thanks for looking.