请好心人帮忙！请用C++语言实现！谢谢

Given a BMP image, write a program that puts in a black cross shape on the image.

a. Assume that the cross is the darkest black

b. The input to your program is the BMP image, and the cross specifications (origin, height in pixels, width of the lines in pixels)

c. Optional (priority to those that can do this): implement the cross finding algorithm based on a BMP image as the matrix.