Remember that in images, white is data present. When you superimpose the large amounts of white from the top image on top of the grid on the bottom, then almost everything is going to turn white, leaving you with only a few dots where the curved line from the first happens to intersect the grid.
You may wish to consider converting to black and white, then inverting the image so that the black becomes true, doing a logical or of the two, then inverting again.
