ChartDetect - detects calibration charts

NAME

ChartDetect

SYNOPSIS

ChartDetect [ -i pgm file ] [ -o file ] [ -f file ] [ -dim integer] [ -t ] [ -c ] [ -q ] [ -h ] [debug & other options]

DESCRIPTION

ChartDetect implements a fast and robust recognition approach for the detection of a common calibration chart as described in "Three Dimensional Reconstruction", M.Phil to D.Phil Transfer Report of L.M. Soh, University of Surrey. It takes as its input an image of calibration chart(s). ChartDetect will attempt to find the best possible charts in a reasonable image, using various constraints with Attributed Graph Matching approach. The outputs of this function can then be channelled to any calibration routine (eg. Tsai's camera calibration) to obtain 3D information of the Calibration Chart.

COMPULSORY ARGUMENTS

-i <input image (P5 pgm)> - specifies the input pgm file to be used.

USEFUL INPUT OPTIONS:

-dim (4) [4] - gives the size of the calibration chart.

USEFUL OUTPUT OPTIONS:

-m (0) [0] - generates the edge map of the whole image.

-t (0) [0] - generates the centre of each chart's squares.

-c (0) [0] - generates a line linking the centre of each chart's squares.

-q (0) [0] - generates each chart's square edge.

-h (0) [0] - generates each chart's ideal square edge.

-o <output .gf file> - generates a gf format file <file> of the specified output options.

-f <output Tsai's calibration format> - generates file(s) <file1..file*> to be used as input for Tsai's camera calibration shareware.

DEBUG AND OTHER OPTIONS:

-grd (4.000) [4.000] - gives the minimum limit of the maximum local gradient to the global gradient ratio.

-whi (8.000) [8.000] - gives the minimum limit of the white-Black gradient change to the maximum gradient ratio.

-thr (5.000) [5.000] - gives the minimum limit of the higher to lower threshold ratio.

-str (1.100) [1.100] - gives the minimum limit of the string length to the string gap ratio.

-cpa (60.000) [60.000] - gives the maximum limit of the compactness (perimeter^2/area).

-cvx (1.280) [1.280] - gives the maximum limit of the convexity (convex hull area /compact area).

-psp (1.800) [1.800] - gives the maximum limit of the ((search Distance/2)/string) length ratio.

-vec (0.060) [0.060] - gives the maximum limit of the vector errors.

-var (120.000) [120.000] - gives the maximum limit of the square of the vector variance.

-dir (0.400) [0.400] - gives the maximum limit of the direction(radian) difference.

-are (0.750) [0.750] - gives the maximum limit of the distorted to normal area ratio

-xbs (12.000) [12.000] - gives the maximum limit of the big to small loop ratio.

-nbs (2.000) [2.000] - gives the minimum limit of the big to small loop ratio.

-rim (4) [4] - excludes the 'rim' blocks in maximum gradient computation.

-blk (32) [32] - gives the block size for the local gradient maxima.

-gap (8) [8] - gives the maximum limit of the area for gap bridging.

-sho (5) [5] - remove side branches shorter then x.

-ard (10) [10] - accepts 2xarea difference of less than or equal to x

-drf (4) [4] - accepts centres difference of less than or equal to x.

-wgt (200) [200] - gives the minimum limit of the chart weight.

-n (0) [0] - generates the edges and junctions detected.

-g (0) [0] - generates the gaps from gap bridging.

-e (0) [0] - generates all possible closed loops after gap bridging.

-a (0) [0] - generates all possible closed loops after compactness check.

-x (0) [0] - generates all possible closed loops after the convexity check.

-r (0) [0] - generates all the centres of all possible loops after the convexity check.

-help (1) [0] - prints out usage information

EXAMPLE:

example1% ChartDetect -i test-images/1.pgm -p /tmp/t

This command gives an output file(s) /tmp/t* for input to Tsai's camera calibration.

example2% ChartDetect -i test-images/1.pgm -o /tmp/g -m -t

This command writes the edgemap of test-images/1.pgm and centre of each chart's squares into a gf format output file /tmp/g.

POSTSCRIPT FILES OF CALIBRATION CHARTS

The location of the input calibration charts in postscript format can be found in /vol/vssp/vap/soft/chart directory. The square charts are chart44.ps (one 14x14cm) and chart44_small.ps (one 7x7cm). The circle charts are circle44.ps (one 14x14cm), circle444_small.ps (four 7x7cm charts) and circle44_small.ps (one 7x7cm).

BUGS

Please inform me if it's not working well.

SEE ALSO

paste(1), ccal(1), ccal_fo(1), ecal(1), gf(3), xgf(n)

AUTHOR

Alan Soh L.M. (L.Soh@ee.surrey.ac.uk), University of Surrey, 1st July 1997. Thanks to George (Jiri) Matas (g.matas@ee.surrey.ac.uk) who contributed the source codes for low level image processing.
23-Nov-97. Automatically converted by man2html, written by G.Matas (g.matas@ee.surrey.ac.uk)