#!/bin/bash
## img2transparent -- make the background be transparent -- by Eugene Reimer 2005July
## USAGE:
##	img2transparent  InputFile  [ResultFile]    -- produces InputFile.gif when ResultFile omitted;  handles ResultFile same as InputFile

F=${1##*/}; B=${F%.*};  OF=$B.gif						##default resultfile is $1 without directory-part, and with suffix replaced by gif
[ $# -ge 2 ] && OF=$2;								##optional 2nd param is the result-name;  2007apr: added, so cam make a PNG
echo "--img2transparent: Input=$1 Output=$OF"					##DEBUG
[ -e "$OF" ] && cp -pfv $OF $OF~						##make bkup of file to be overwritten

if [[ $1 == *ppm ]];then PPM=$1; else PPM=tmp$$.ppm; convert $1 $PPM; fi	##Convert input image to PPM

pnmcut 0 0 1 1 $PPM |pamtopnm -plain  >tmp$$C1plain.ppm				##Isolate the top-left pixel, as a plain-ppm
{ read; read; read;								##read that plain-text ppm...
  read -a PIX;  ((Red=PIX[0])); ((Green=PIX[1])); ((Blue=PIX[2]));		##get that pixel's color as Red, Green, Blue components
}  <tmp$$C1plain.ppm								##2006nov: converted to "the better way" to set vars
color=$(printf '#%02x%02x%02x' $Red $Green $Blue)				##convert to 6-hex-digit color
echo "--Top-Left pixel: Red=$Red; Green=$Green; Blue=$Blue; color=$color"	##DEBUG

##-- 2005jul: METHOD-1 (ppmtogif EXACT-match):
##ppmquant -meanpixel 256 $PPM |ppmtogif -transparent $color >$OF		##create transparent GIF;  works but without fuzzy-matching

##-- 2006nov26: METHOD-3A (convert-draw with fuzzy-match):
##convert -fuzz 10%            -draw 'matte 0,0 replace'  $1  $OF		##create transparent GIF/PNG -- DOES NOTHING (did I misread the documentation??)
##convert -fill none -fuzz 10% -draw 'matte 0,0 replace'  $1  $OF		##create transparent GIF/PNG -- does something, but not the fuzzy-matching...
##convert -fuzz 10% -fill none -draw 'matte 0,0 replace'  $1  $OF		##create transparent GIF/PNG -- also no fuzzy-matching ==> give up on -matte method

##-- 2006nov26: METHOD-2A (convert-transparent with fuzzy-match):
##convert -fuzz 1% -transparent $color  $PPM  $OF				##create transparent GIF/PNG -- DOES FUZZY-MATCHING (-fuzz must precede -transparent)
										##fuzz:10% fine for most logos;  but needed 1% for DonateNow3BA, NathanVadeboncoeur-FigA
										##fuzz:1% fuzz:1 both match way too too much on the Debwendon-logo (both std+forDark)
										##convert's fuzzy-match uses transitive-closure => is unusable on antialiased img:-(
##-- 2008-04-27: METHOD-1A (with ppmchange fuzzy-matching)
ppmto=ppmtogif; if [[ $OF == *png ]];then ppmto=pnmtopng; fi			##handle gif or pgm output
if [[ $OF == *png ]];then
  ppmchange -closeness=12 $color $color $PPM                          |$ppmto -transparent $color  >$OF		##NetPBM fuzzy-matching;  skip ppmquant for PNG output
else
  ppmchange -closeness=12 $color $color $PPM |ppmquant -meanpixel 256 |$ppmto -transparent $color  >$OF		##NetPBM fuzzy-matching for GIF output
fi
rm tmp$$*ppm


exit
## COMPARISON OF METHODS:
## ======================
## 1.  ppmtogif -transparent $color  x.ppm  >x.gif
##	-- doesn't need ImageMagick;  is exact-match only, and no neighbouring-pixels variant;
##	-- produces Compressed-GIF!  (my RH7 version of ImageMagick-convert didn't)
##
## 2.  convert -transparent $color  x.ppm  x.gif
##	-- Variant-A:  supply -fuzz NN  in order to get fuzzy-matching
##
## 3.  convert -draw 'matte 0,0 replace'  x.ppm  x.gif
##	-- Variant-A:  supply -fuzz NN  in order to get fuzzy-matching;
##	-- Variant-B:  using "floodfill" in place of "replace" produces a neighbours-only replacement method;
##		useful when interior pixels of that color are to retain that colour (usually NOT wanted);
##	-- Variant-C:  can use "color" in place of "matte" to replace with a specified colour (instead of clear); it is specified as: -fill COLOR
##
## CHANGE-LOG:
## ===========
## 2005-Jul: implemented METHOD-1 (ppmtogif);
## 2006-Nov: when trying photographic-background on the index.htm page, noticed the logo looked hideous on that darker background (way too much near-white);
##	WANTED: fuzzy-matching Method-2/3 Variant-A  (OpenOffice fine with fuzzy-match:30 on 200x200 logo;  convert seems ok with 10% = 25.6 absolute)
## 2007-Apr: respect the filetype-suffix of 2nd param -- so can make a transparent PNG (default remains Inputfile.gif)
## 2007-June: encountered situations where Bottom-Left or Bottom-Right corner was needed to get the right background;
##	      and where "neighbours only" replacement was needed -- handled them semi-manually...
## 2008-Apr: couldn't get convert's fuzzy-matching to behave on Debwendon logo;  deduced it uses transitive-closure on the near-test - altho that's downright stupid!!
##	switched to the NetPBM-equivalent;  need ppmquant that leaves "dominant" colours unchanged -- with the -meanpixel option it comes fairly close to what I want;
## 2008-Nov: minor changes to tidy up.