The --bpp and --noimages
options can be used to globally set the image handling. The --bpp
option takes an argument for the bits per pixels that should be used,
0, 1 (default), 2, 4, or 8. The --noimages option sets the
bit depth to 0. To include images in 16 colors (grayscale) you would use,
% Spider.py -bpp=4 -H plucker:/images.html -f Gray16DB