/* Last edited on 2006-04-21 13:56:20 by stolfi */

  "  For each computed image, one may either specify a single" \
  " formula for all channels, or use the \"-channel\" option" \
  " to specify a different formula for each channel.\n" \
  "  When \"-channel {NUM}\" is specified, the formula" \
  " must yield a single-channel image, and the depth (number" \
  " of channels) {NC} of the result will be the largest channel" \
  " index {NUM} specified for it, plus one.\n" \
  "  When \"-channel {NUM}\" is omitted, the" \
  " depth {NC} of the resulting image" \
  " depends on the outermost operation in the formula." \