image processing algorithm for filling

I am going to try but in the meantime if anybody wants to help ... I have a 2-D image in black, white and red. Going across each row, I want to change white and red pixels to black if they are surrounded by a red border and black pixels. for each row A if pixel(a,A) = black; pixel(b,A) = red; and pixel(c,A) = white; then make all pixels black until pixel(x,A) = white; pixel(y,A) = red; and pixel(c,A) = is black

[Image Analyst]

Please post your image so we can see it and offer advice or code.