If the image lines are say 1 pixel thick when you zoom out they'll vanish - but then of course thin mortar joints in masonry can't be really seen from a distance either ! Try making the fully black lines in the image 2 pixels wide and see it that helps... You can imagine if the images lines were 10px wide you'd probably see them ! Edges/profiles are in a specified pixel width, irrespective of their distance from the viewer, so an edge is say always 2px wide no matter where it is in 3d; but images have a total fixed pixel width, so if you move far enough away they will become feint or invisible - if a whole image occupies just 10px 'on screen', but its 'real' size is let's say 300px, it needs to be 'down-sampled' to fit into the 10, so detail is lost ! ... The converse of that is that multiple edges when seen far away can look like a 'black=blob' because they all become 2px each, fitting into a small screen area of a few pixels, leaving no visible 'gaps' between each other !