#!/bin/bash # # Developed by Fred Weinhaus 10/29/2008 .......... revised 1/18/2020 # # ------------------------------------------------------------------------------ # # Licensing: # # Copyright © Fred Weinhaus # # My scripts are available free of charge for non-commercial use, ONLY. # # For use of my scripts in commercial (for-profit) environments or # non-free applications, please contact me (Fred Weinhaus) for # licensing arrangements. My email address is fmw at alink dot net. # # If you: 1) redistribute, 2) incorporate any of these scripts into other # free applications or 3) reprogram them in another scripting language, # then you must contact me for permission, especially if the result might # be used in a commercial or for-profit environment. # # My scripts are also subject, in a subordinate manner, to the ImageMagick # license, which can be found at: http://www.imagemagick.org/script/license.php # # ------------------------------------------------------------------------------ # #### # # USAGE: trianglethresh [-g graph] infile outfile # USAGE: trianglethresh [-help] # # OPTIONS: # # -g graph graph specifies whether to generate a # histogram graph image displaying the # location and value of the threshold; # choices are: view or save; # default is no graph # ### # # NAME: TRIANGLETHRESH # # PURPOSE: To automatically thresholds an image to binary (b/w) format # using the triangle technique. # # DESCRIPTION: TRIANGLETHRESH automatically thresholds an image to binary # (b/w) format. It does not assume the histogram is bimodal. It finds the # bin with the highest value (the peak in the histogram) and also the end # of the histogram furthest from the peak. It then draws a line between # the two. It exhaustively searches along the line drawing a perpendicular # from the line to the top of each histogram bin and picks the threshold # value at that bin for which the perpendicular is the longest. # # OPTIONS: # # -g graph ... GRAPH specifies whether to generate a graph (image) of # the histogram, displaying the location and value of the threshold. # The choices are: view, save and none. If graph=view is selected, the # graph will be created and displayed automatically, but not saved. # If graph=save is selected, then the graph will be created and saved # to a file using the infile name, with "_histog_triangle.gif" appended, # but the graph will not be displayed automatically. If -g option is # not specified, then no graph will be created. # # NOTE: It is highly recommended that the output not be specified # as a JPG image as that will cause compression and potentially a # non-binary (i.e. a graylevel) result. GIF is the recommended # output format. # # REFERENCES: see the following: # http://www.ph.tn.tudelft.nl/Courses/FIP/noframes/fip-Segmenta.html # # CAVEAT: No guarantee that this script will work on all platforms, # nor that trapping of inconsistent parameters is complete and # foolproof. Use At Your Own Risk. # ###### # # set default values graph="" #none, save or view # set directory for temporary files dir="." # suggestions are dir="." or dir="/tmp" # set up functions to report Usage and Usage with Description PROGNAME=`type $0 | awk '{print $3}'` # search for executable on path PROGDIR=`dirname $PROGNAME` # extract directory of program PROGNAME=`basename $PROGNAME` # base name of program usage1() { echo >&2 "" echo >&2 "$PROGNAME:" "$@" sed >&2 -e '1,/^####/d; /^###/g; /^#/!q; s/^#//; s/^ //; 4,$p' "$PROGDIR/$PROGNAME" } usage2() { echo >&2 "" echo >&2 "$PROGNAME:" "$@" sed >&2 -e '1,/^####/d; /^######/g; /^#/!q; s/^#*//; s/^ //; 4,$p' "$PROGDIR/$PROGNAME" } # function to report error messages errMsg() { echo "" echo $1 echo "" usage1 exit 1 } # function to test for minus at start of value of second part of option 1 or 2 checkMinus() { test=`echo "$1" | grep -c '^-.*$'` # returns 1 if match; 0 otherwise [ $test -eq 1 ] && errMsg "$errorMsg" } # test for correct number of arguments and get values if [ $# -eq 0 ] then # help information echo "" usage2 exit 0 elif [ $# -gt 4 ] then errMsg "--- TOO MANY ARGUMENTS WERE PROVIDED ---" else while [ $# -gt 0 ] do # get parameter values case "$1" in -h|-help) # help information echo "" usage2 exit 0 ;; -g) # get graph shift # to get the next parameter # test if parameter starts with minus sign errorMsg="--- INVALID GRAPH SPECIFICATION ---" checkMinus "$1" graph="$1" [ "$graph" != "view" -a "$graph" != "save" ] && errMsg "--- GRAPH=$graph MUST BE EITHER VIEW OR SAVE ---" ;; -) # STDIN and end of arguments break ;; -*) # any other - argument errMsg "--- UNKNOWN OPTION ---" ;; *) # end of arguments break ;; esac shift # next option done # # get infile and outfile infile="$1" outfile="$2" fi # test that infile provided [ "$infile" = "" ] && errMsg "NO INPUT FILE SPECIFIED" # test that outfile provided [ "$outfile" = "" ] && errMsg "NO OUTPUT FILE SPECIFIED" # get outname from infile to use for graph inname=`convert $infile -format "%t" info:` histfile="${inname}_histog_triangle.gif" tmpA1="$dir/trianglethresh_1_$$.mpc" tmpA2="$dir/trianglethresh_1_$$.cache" trap "rm -f $tmpA1 $tmpA2; exit 0" 0 trap "rm -f $tmpA1 $tmpA2 $histfile; exit 1" 1 2 3 15 # get im_version im_version=`convert -list configure | \ sed '/^LIB_VERSION_NUMBER */!d; s//,/; s/,/,0/g; s/,0*\([0-9][0-9]\)/\1/g' | head -n 1` # colorspace RGB and sRGB swapped between 6.7.5.5 and 6.7.6.7 # though probably not resolved until the latter # then -colorspace gray changed to linear between 6.7.6.7 and 6.7.8.2 # then -separate converted to linear gray channels between 6.7.6.7 and 6.7.8.2, # though probably not resolved until the latter # so -colorspace HSL/HSB -separate and -colorspace gray became linear # but we need to use -set colorspace RGB before using them at appropriate times # so that results stay as in original script # The following was determined from various version tests using trianglethresh. # with IM 6.7.4.10, 6.7.6.10, 6.7.8.10 if [ "$im_version" -lt "06070607" -o "$im_version" -gt "06070707" ]; then setcspace="-set colorspace RGB" else setcspace="" fi # no need for setcspace for grayscale or channels after 6.8.5.4 if [ "$im_version" -gt "06080504" ]; then setcspace="" fi if convert -quiet "$infile" $setcspace -colorspace gray +repage "$tmpA1" then : ' do nothing ' else errMsg "--- FILE $infile DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAG ZERO SIZE ---" fi # get totpix in image width=`convert $tmpA1 -format "%w" info:` height=`convert $tmpA1 -format "%h" info:` totpix=`echo "scale=0; $width * $height / 1" | bc` # separate IM histogram into two arrays, value and count, and fill out for empty bins and normalize # get filled value array from IM histogram nvalueArr=(`convert $tmpA1 -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- \ | sed -n 's/[ ]*\([0-9]*\).*gray[(]\([0-9]*\).*$/\1 \2/p' |\ awk ' # AWK { vbin[$2] += $2;} END { for (i=0;i<256;i++) {print vbin[i]+0; } } '`) # echo ${nvalueArr[*]} # echo ${#nvalueArr[*]} numvals=${#nvalueArr[*]} # get filled and normalized count array from IM histogram ncountArr=(`convert $tmpA1 -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- \ | sed -n 's/[ ]*\([0-9]*\).*gray[(]\([0-9]*\).*$/\1 \2/p' |\ awk -v totpix="$totpix" ' # AWK { cbin[$2] += $1; } END { for (i=0;i<256;i++) {print (cbin[i]+0)/totpix; } } '`) # echo ${ncountArr[*]} # echo ${#ncountArr[*]} numcounts=${#ncountArr[*]} [ $numvals -ne $numcounts ] && errMsg "--- NUMBER OF COUNTS IS NOT THE SAME AS NUMBER OF VALUES ---" # find start bin (first one not zero) startbin=`for ((i=0; i<256; i++)); do echo "$i ${ncountArr[$i]}" done |\ awk ' # AWK to find startbin { cbin[$1] = $2; } END { for (i=0;i<256;i++) { if (cbin[i]!=0) { print i; break; } } } '` eval startbincount=${ncountArr[$startbin]} # echo "startbin=$startbin; startbincount=$startbincount;" # find end bin (last one not zero) endbin=`for ((i=0; i<256; i++)); do echo "$i ${ncountArr[$i]}" done |\ awk ' # AWK to find startbin { cbin[$1] = $2; } END { for (i=255;i>=0;i--) { if (cbin[i]!=0) { print i; break; } } } '` endbincount=${ncountArr[$endbin]} # echo "endbin=$endbin; endbincount=$endbincount;" # find max bin (bin with largest count) maxbin=`for ((i=0; i<256; i++)); do echo "$i ${ncountArr[$i]}" done |\ awk ' # AWK to find startbin { cbin[$1] = $2; maxbincount = 0; maxbin = 0; } END { for (i=0;i<256;i++) { if (cbin[i] > maxbincount) { maxbincount=cbin[i]; maxbin=i; } } print maxbin } '` maxbincount=${ncountArr[$maxbin]} # echo "maxbin=$maxbin; maxbincount=$maxbincount;" # set x1,y1 for bin with max count y1=$maxbincount x1=$maxbin # set x2,y2 for furthest end bin from bin with max count lowdiff=`expr $maxbin - $startbin` highdiff=`expr $endbin - $maxbin` if [ $lowdiff -ge $highdiff ]; then x2=$startbin y2=0 else x2=$endbin y2=0 fi #echo "lowdiff=$lowdiff; highdiff=$highdiff; x1=$x1; y1=$y1; x2=$x2; y2=$y2" # compute threshold # equation of line between x1,y1 and x2,y2 is Ax+By+C=0 # where A=(y1-y2), B=(x2-x1), C=-(A*x1+B*y1) # Dist=abs(A*x1+B*y1+C)/sqrt(A^2+B^2+C^2) aa=`echo "scale=10; ($y1 - $y2)/1" | bc` bb=`echo "scale=10; ($x2 - $x1)/1" | bc` cc=`echo "scale=10; -($aa*$x1 + $bb*$y1)/1" | bc` ir=`echo "scale=10; 1/sqrt($aa*$aa + $bb*$bb + $cc*$cc)" | bc` #echo "aa=$aa; bb=$bb; cc=$cc; ir=$ir" # increment from appropriate end to bin with max count # and compute dist and save bin where dist is max if [ $x2 -eq $startbin ]; then distbin=`for ((i=0; i<256; i++)); do echo "$i ${ncountArr[$i]}" done |\ awk -v startbin="$startbin" -v maxbin="$maxbin" -v aa="$aa" -v bb="$bb" -v cc="$cc" -v ir="$ir" ' # AWK to find threshold { x[$1] = $1; y[$1] = $2; dist=0; } END { for (i=startbin;idist && dd>0) { distbin=i; dist=ddabs; } } print distbin } '` # echo "$distbin" else distbin=`for ((i=0; i<256; i++)); do echo "$i ${ncountArr[$i]}" done |\ awk -v endbin="$endbin" -v maxbin="$maxbin" -v aa="$aa" -v bb="$bb" -v cc="$cc" -v ir="$ir" ' # AWK to find threshold { x[$1] = $1; y[$1] = $2; dist=0; } END { for (i=endbin;i>maxbin;i--) { dd = ir*(aa*x[i]+bb*y[i]+cc); ddabs = sqrt(dd*dd); if (ddabs>dist && dd<0) { distbin=i; dist=ddabs; } } print distbin } '` # echo "$distbin" fi # set threshold to value (0 to 255) of bin where dist is max x0=$distbin y0=${ncountArr[$distbin]} #echo "x0=$x0; y0=$y0" # convert threshold value to range 0 to 100 threshpct=`convert xc: -format "%[fx:100*$x0/255]" info:` echo "Thresholding Image At $threshpct%" # threshold image convert $tmpA1 -threshold $threshpct% "$outfile" echo "" if [ "$graph" != "" ]; then # compute triangle lines for graphing # histogram image scales maxbincount to 200 pixels # counts need to be complemented with 200 # as 0 is at image top and 200 at image bottom # convert y1 and y2 to points on histogram image xx1=$x1 yy1=0 xx2=$x2 yy2=200 # echo "xx1=$xx1; yy1=$yy1; xx2=$xx2; yy2=$yy2" # convert x0,y0 to point on histogram image xx0=$x0 yy0=`echo "scale=10; 200*(1 - $y0/$y1)/1" | bc` #echo "y0=$y0; y1=$y1; yy0=$yy0" # find intersection of perpendicular through xx0,yy0 and line between xx1,yy1 and x2,y2 # get slope and intercept of line between xx1,yy1 and xx2,yy2 sl=`echo "scale=10; ($yy2 - $yy1)/($xx2 - $xx1)" | bc` il=`echo "scale=10; ($yy1 - $sl*$xx1)/1" | bc` # get slope and intercept of perpendicular # slope is negative inverse of that of line between xx1,yy1 and xx2,yy2 sp=`echo "scale=10; -1/$sl" | bc` ip=`echo "scale=10; ($yy0 - $sp*$xx0)/1" | bc` # compute intersection point xx3,yy3 xx3=`echo "scale=10; ($ip - $il)/($sl - $sp)" | bc` yy3=`echo "scale=10; ($sl*$xx3 + $il)/1" | bc` # echo "sl=$sl; il=$il; sp=$sp; ip=$ip; xx3=$xx3; yy3=$yy3" # echo "xx0=$xx0; yy0=$yy0; xx3=$xx3; yy3=$yy3" convert $tmpA1 -define histogram:unique-colors=false histogram:- | \ convert - -negate \ -stroke blue -strokewidth 1 -draw "line $xx1,$yy1 $xx2,$yy2" \ -stroke green1 -strokewidth 1 -draw "line $xx0,$yy0 $xx3,$yy3" \ -stroke red -strokewidth 1 -draw "line $xx0,0 $xx0,200" \ -background gray -splice 0x30 \ -fill white -stroke white -strokewidth 1 \ -font ArialB -pointsize 24 \ -draw "text 4,22 'threshold=$threshpct%'" -resize 50% \ -bordercolor gray50 -border 5 \ "$histfile" fi if [ "$graph" = "view" ]; then convert $histfile x: rm -f "$histfile" fi exit 0