If I understood the original post correctly, he wanted to draw a few lines, then rasterize the result to an UInt8 matrix, and repeat that whole process hundreds of millions of times. I haven’t benchmarked it, but I would suspect that this can be done considerably faster on pure CPU writing straight to the UInt8 matrix (~1 μs per line), than on GPU and transfer the results to system memory for each frame. Don’t you think?
If he wants to draw more complex shapes, and/or more than a few lines, that’s a different situation, but then it probably needs to be looked at in a broader perspective, not just what’s the fastest way to rasterize an image regardless of plotting library, but the fastest overall to draw the desired shapes and get the resulting image.