mrgingham-rotate-corners

#!/bin/bash

# Takes a processed corners.vnl result, and rotates some of the chessboard
# observations. Used if some of the cameras in the calibrated set were mounted
# sideways or upside-down



# Option parsing is the adapted sample in
# /usr/share/doc/util-linux/examples/getopt-example.bash

usage="
  < corners.vnl                        \\
  mrgingham-rotate-corners [--gridn N] \\
    --90  REGEX_CAM_90deg              \\
    --180 REGEX_CAM_180deg             \\
    --270 REGEX_CAM_270deg             \\
    [... more rotation selections ...] \\
  > corners-rotated.vnl

Adjust mrgingham corner detections from rotated cameras

Synopsis:

  # camera A is rightside-up
  # camera B is mounted sideways
  # cameras C,D are upside-down
  mrgingham --gridn N                \\
    'frame*-cameraA.jpg'             \\
    'frame*-cameraB.jpg'             \\
    'frame*-cameraC.jpg'             \\
    'frame*-cameraD.jpg' |           \\
  mrgingham-rotate-corners --gridn N \\
    --90 cameraB --180 'camera[CD]'

The mrgingham chessboard detector finds a chessboard in an image, but it has no
way to know whether the detected chessboard was upside-down or otherwise
rotated: the chessboard itself has no detectable marking to make this clear. In
the usual case, the cameras as all mounted in the same orientation, so they all
detect the same orientation of the chessboard, and there is no problem. However,
if some cameras are mounted sideways or upside-down, the sequence of corners
will correspond to different corners between the cameras with different
orientations. This can be addressed by this tool. This tool ingests mrgingham
detections, and outputs them after correcting the chessboard observations
produced by rotated cameras.

Each rotation option is an awk regular expression used to select images from
specific cameras. The regular expression is tested against the image filenames.
Each rotation option may be given multiple times. Any files not matched by any
rotation option are passed through unrotated.
"

ARGS=$(getopt -n $0 -l help,gridn:,90:,180:,270: -o "h" -- "$@")

if [ $? -ne 0 ]; then
	echo "Usage: $usage" > /dev/stderr
	exit 1
fi

eval set -- "$ARGS"
unset ARGS


gridn=10
cam_rotate90=()
cam_rotate180=()
cam_rotate270=()

while true; do
	case "$1" in
            '--help'|'-h')
                echo "Usage: $usage"
                exit 0
                ;;
            '--gridn')
                gridn=$2
                shift 2
                continue
                ;;
            '--90')
                cam_rotate90+=($2)
                shift 2
                ;;
            '--180')
                cam_rotate180+=($2)
                shift 2
                ;;
            '--270')
                cam_rotate270+=($2)
                shift 2
                ;;
            '--')
                shift
                break
                ;;
            *)
                echo "Error parsing options!" > /dev/stderr
                exit 1
                ;;
        esac
done

if (( $# )); then
    echo "Extra arguments given" > /dev/stderr
    echo "Usage: $usage"         > /dev/stderr
    exit 1
fi

cam_rotate90_select_expression="0"
for f in ${cam_rotate90[@]}; do
    cam_rotate90_select_expression+=" || filename ~ \"$f\""
done
cam_rotate180_select_expression="0"
for f in ${cam_rotate180[@]}; do
    cam_rotate180_select_expression+=" || filename ~ \"$f\""
done
cam_rotate270_select_expression="0"
for f in ${cam_rotate270[@]}; do
    cam_rotate270_select_expression+=" || filename ~ \"$f\""
done

Nx=$gridn
Ny=$gridn
Nxy=$((Nx*Ny))

ICORNER_FUNCTION="
if(filename!=filename_prev) {

  N=i+1
  if(!(N == 0 || N == 1 || N == $Nxy)) {
    print \"# File '\"filename\"': expected \"$Nxy\" points but received \"N > \"/dev/stderr\";
    failed=1;
    exit 1
  }

  i =0;
  ix=0;
  iy=0;
  filename_prev=filename;
}
else {
  i++;
  ix++;
  if(ix == $Nx) {
    ix = 0;
    iy++;
  }
}

if($cam_rotate90_select_expression)
  return ($Nx-1-ix)*$Ny + iy;
if($cam_rotate270_select_expression)
  return ix*$Ny + ($Ny-1-iy);
if($cam_rotate180_select_expression)
  return ($Nx*$Ny-1 - i);
return i;
"

END_EXPRESSION="
  N=i+1
  if(!failed && !(N == 0 || N == 1 || N == $Nxy)) {
    print \"# The last file in the data file expected \"$Nxy\" points but received \"N > \"/dev/stderr\";
    exit 1
  }
"


vnl-filter \
  --skipcomments \
  --end "$END_EXPRESSION" \
  --sub "icorner() { $ICORNER_FUNCTION }" \
  -p icorner='icorner()',. \
| vnl-sort -k filename -k icorner.n \
| vnl-filter -p '!icorner'

exit ${PIPESTATUS[0]}