#!/bin/bash
## mkfavicon-transparent -- convert any image into a transparent image in the FAVICON-format -- by Eugene Reimer, 2007-Apr;
## using png2ico, since it's simpler when wanting transparency (compared to ppmtowinicon, as used by mkfavicon for nontransparent favicon-making);
## note: uses TOP-LEFT pixel to get the colour that's to become transparent;  done in img2transparent, which uses fuzzy-matching;
##
## the ppmtowinicon documentation says Microsoft recommends including 16x16 (16-color), 32x32 (16-color), and 48x48 (256-color) images;
## but that seems a waste of bandwidth, as it makes a big file, and most browsers never use anything other than 16x16;
## I made nativeorchid's favicon.ico that way (except for max 64-colors?), for a filesize of 3638 bytes;
## making it with only the first two image-sizes, yields a filesize of 1078 bytes;
## using only a 16x16 image, yields a filesize of 318 bytes;  (these filesizes are independent of image complexity, transparency, etc)
##
## if input image is smaller than 32x32, then makes only the 16x16 size;  otherwise makes both 16x16 and 32x32 sizes, each in 16-colours.

OF=favicon.ico;  [ $# -ge 2 ] && OF=$2;				##optional 2nd param is the result-name (default: favicon.ico)
convert $1 tmp$$.ppm						##convert input to PPM
w=$(pnmfile tmp$$.ppm |gawk '{ print $4 }')			##get w=width of image
h=$(pnmfile tmp$$.ppm |gawk '{ print $6 }')			##get h=height of image
pnmscale   -xysize 16 16 tmp$$.ppm 2>/dev/null >tmp$$16r.ppm;  pnmquant 16 tmp$$16r.ppm >tmp$$16q.ppm;  img2transparent tmp$$16q.ppm tmp$$16.png  ##to 16x16 in 16-colors
if ((w*h >= 32*32)); then
  pnmscale -xysize 32 32 tmp$$.ppm 2>/dev/null >tmp$$32r.ppm;  pnmquant 16 tmp$$32r.ppm >tmp$$32q.ppm;  img2transparent tmp$$32q.ppm tmp$$32.png  ##to 32x32 in 16-colors
  png2ico $OF --colors 16 tmp$$16.png tmp$$32.png		##produce favicon output file containing both 16x16 and 32x32 images
  echo "wrote $OF with 16x16 and 32x32 images"
else
  png2ico $OF --colors 16 tmp$$16.png				##produce favicon output file containing only 16x16 image
  echo "wrote $OF with 16x16 image only"
fi

rm tmp$$*							##yank to debug using tmp files