How to change the score of reads to be negative on the antisense chain of the genome from bam file

Question

[17318598206]

hello everyone, i have chip-seq dada, i have got the BAM file by mapping, then i extracted and compared reads on the forward and reverse strands,

now i want to change the score of reads to be negative on the reverse strand from bam file, so that allows me to visualize the peak in different directions,like this: https://data.cyverse.org/dav-anon/iplant/home/xucaoling/forward_reverse.png

so, how to make it?

thank you!