Converting hls::stream<ap_axiu<64,1,1,1>> to hls::Mat<>

I was looking to setup the the base overlay pipeline with a resolution 12 bit per channel with one pixel per clock cycle. The thing is that by the time the data is getting to the vdma, I just want to reduce it down to one channel since I am working with gray scale image. Is this possible with the base overlay with minor tweak to it?