ref: b6ee9debcfe46c7ed4e958511e754f150f4e9773
dir: /icons/icon.pl/
#!/usr/bin/perl
# Take a collection of input image files and convert them into a
# multi-resolution Windows .ICO icon file.
#
# The input images can be treated as having four different colour
# depths:
#
# - 24-bit true colour
# - 8-bit with custom palette
# - 4-bit using the Windows 16-colour palette (see comment below
# for details)
# - 1-bit using black and white only.
#
# The images can be supplied in any input format acceptable to
# ImageMagick, but their actual colour usage must already be
# appropriate for the specified mode; this script will not do any
# substantive conversion. So if an image intended to be used in 4-
# or 1-bit mode contains any colour not in the appropriate fixed
# palette, that's a fatal error; if an image to be used in 8-bit
# mode contains more than 256 distinct colours, that's also a fatal
# error.
#
# Command-line syntax is:
#
# icon.pl -depth imagefile [imagefile...] [-depth imagefile [imagefile...]]
#
# where `-depth' is one of `-24', `-8', `-4' or `-1', and tells the
# script how to treat all the image files given after that option
# until the next depth option. For example, you might execute
#
# icon.pl -24 48x48x24.png 32x32x24.png -8 32x32x8.png -1 monochrome.png
#
# to build an icon file containing two differently sized 24-bit
# images, one 8-bit image and one black and white image.
#
# Windows .ICO files support a 1-bit alpha channel on all these
# image types. That is, any pixel can be either opaque or fully
# transparent, but not partially transparent. The alpha channel is
# separate from the main image data, meaning that `transparent' is
# not required to take up a palette entry. (So an 8-bit image can
# have 256 distinct _opaque_ colours, plus transparent pixels as
# well.) If the input images have alpha channels, they will be used
# to determine which pixels of the icon are transparent, by simple
# quantisation half way up (e.g. in a PNG image with an 8-bit alpha
# channel, alpha values of 00-7F will be mapped to transparent
# pixels, and 80-FF will become opaque).
# The Windows 16-colour palette consists of:
# - the eight corners of the colour cube (000000, 0000FF, 00FF00,
# 00FFFF, FF0000, FF00FF, FFFF00, FFFFFF)
# - dim versions of the seven non-black corners, at 128/255 of the
# brightness (000080, 008000, 008080, 800000, 800080, 808000,
# 808080)
# - light grey at 192/255 of full brightness (C0C0C0).
%win16pal = (
"\x00\x00\x00\x00" => 0,
"\x00\x00\x80\x00" => 1,
"\x00\x80\x00\x00" => 2,
"\x00\x80\x80\x00" => 3,
"\x80\x00\x00\x00" => 4,
"\x80\x00\x80\x00" => 5,
"\x80\x80\x00\x00" => 6,
"\xC0\xC0\xC0\x00" => 7,
"\x80\x80\x80\x00" => 8,
"\x00\x00\xFF\x00" => 9,
"\x00\xFF\x00\x00" => 10,
"\x00\xFF\xFF\x00" => 11,
"\xFF\x00\x00\x00" => 12,
"\xFF\x00\xFF\x00" => 13,
"\xFF\xFF\x00\x00" => 14,
"\xFF\xFF\xFF\x00" => 15,
);
@win16pal = sort { $win16pal{$a} <=> $win16pal{$b} } keys %win16pal;
# The black and white palette consists of black (000000) and white
# (FFFFFF), obviously.
%win2pal = (
"\x00\x00\x00\x00" => 0,
"\xFF\xFF\xFF\x00" => 1,
);
@win2pal = sort { $win16pal{$a} <=> $win2pal{$b} } keys %win2pal;
@hdr = ();
@dat = ();
$depth = undef;
foreach $_ (@ARGV) {
if (/^-(24|8|4|1)$/) {
$depth = $1;
} elsif (defined $depth) {
&readicon($_, $depth);
} else {
$usage = 1;
}
}
if ($usage || length @hdr == 0) {
print "usage: icon.pl ( -24 | -8 | -4 | -1 ) image [image...]\n";
print " [ ( -24 | -8 | -4 | -1 ) image [image...] ...]\n";
exit 0;
}
# Now write out the output icon file.
print pack "vvv", 0, 1, scalar @hdr; # file-level header
$filepos = 6 + 16 * scalar @hdr;
for ($i = 0; $i < scalar @hdr; $i++) {
print $hdr[$i];
print pack "V", $filepos;
$filepos += length($dat[$i]);
}
for ($i = 0; $i < scalar @hdr; $i++) {
print $dat[$i];
}
sub readicon {
my $filename = shift @_;
my $depth = shift @_;
my $pix;
my $i;
my %pal;
# Determine the icon's width and height.
my $w = `identify -format %w $filename`;
my $h = `identify -format %h $filename`;
# Read the file in as RGBA data. We flip vertically at this
# point, to avoid having to do it ourselves (.BMP and hence
# .ICO are bottom-up).
my $data = [];
open IDATA, "convert -flip -depth 8 $filename rgba:- |";
push @$data, $rgb while (read IDATA,$rgb,4,0) == 4;
close IDATA;
# Check we have the right amount of data.
$xl = $w * $h;
$al = scalar @$data;
die "wrong amount of image data ($al, expected $xl) from $filename\n"
unless $al == $xl;
# Build the alpha channel now, so we can exclude transparent
# pixels from the palette analysis. We replace transparent
# pixels with undef in the data array.
#
# We quantise the alpha channel half way up, so that alpha of
# 0x80 or more is taken to be fully opaque and 0x7F or less is
# fully transparent. Nasty, but the best we can do without
# dithering (and don't even suggest we do that!).
my $x;
my $y;
my $alpha = "";
for ($y = 0; $y < $h; $y++) {
my $currbyte = 0, $currbits = 0;
for ($x = 0; $x < (($w+31)|31)-31; $x++) {
$pix = ($x < $w ? $data->[$y*$w+$x] : "\x00\x00\x00\xFF");
my @rgba = unpack "CCCC", $pix;
$currbyte <<= 1;
$currbits++;
if ($rgba[3] < 0x80) {
if ($x < $w) {
$data->[$y*$w+$x] = undef;
}
$currbyte |= 1; # MS has the alpha channel inverted :-)
} else {
# Might as well flip RGBA into BGR0 while we're here.
if ($x < $w) {
$data->[$y*$w+$x] = pack "CCCC",
$rgba[2], $rgba[1], $rgba[0], 0;
}
}
if ($currbits >= 8) {
$alpha .= pack "C", $currbyte;
$currbits -= 8;
}
}
}
# For an 8-bit image, check we have at most 256 distinct
# colours, and build the palette.
%pal = ();
if ($depth == 8) {
my $palindex = 0;
foreach $pix (@$data) {
next unless defined $pix;
$pal{$pix} = $palindex++ unless defined $pal{$pix};
}
die "too many colours in 8-bit image $filename\n" unless $palindex <= 256;
} elsif ($depth == 4) {
%pal = %win16pal;
} elsif ($depth == 1) {
%pal = %win2pal;
}
my $raster = "";
if ($depth < 24) {
# For a non-24-bit image, flatten the image into one palette
# index per pixel.
$pad = 32 / $depth; # number of pixels to pad scanline to 4-byte align
$pmask = $pad-1;
for ($y = 0; $y < $h; $y++) {
my $currbyte = 0, $currbits = 0;
for ($x = 0; $x < (($w+$pmask)|$pmask)-$pmask; $x++) {
$currbyte <<= $depth;
$currbits += $depth;
if ($x < $w && defined ($pix = $data->[$y*$w+$x])) {
if (!defined $pal{$pix}) {
die "illegal colour value $pix at pixel $i in $filename\n";
}
$currbyte |= $pal{$pix};
}
if ($currbits >= 8) {
$raster .= pack "C", $currbyte;
$currbits -= 8;
}
}
}
} else {
# For a 24-bit image, reverse the order of the R,G,B values
# and stick a padding zero on the end.
#
# (In this loop we don't need to bother padding the
# scanline out to a multiple of four bytes, because every
# pixel takes four whole bytes anyway.)
for ($i = 0; $i < scalar @$data; $i++) {
if (defined $data->[$i]) {
$raster .= $data->[$i];
} else {
$raster .= "\x00\x00\x00\x00";
}
}
$depth = 32; # and adjust this
}
# Prepare the icon data. First the header...
my $data = pack "VVVvvVVVVVV",
40, # size of bitmap info header
$w, # icon width
$h*2, # icon height (x2 to indicate the subsequent alpha channel)
1, # 1 plane (common to all MS image formats)
$depth, # bits per pixel
0, # no compression
length $raster, # image size
0, 0, 0, 0; # resolution, colours used, colours important (ignored)
# ... then the palette ...
if ($depth <= 8) {
my $ncols = (1 << $depth);
my $palette = "\x00\x00\x00\x00" x $ncols;
foreach $i (keys %pal) {
substr($palette, $pal{$i}*4, 4) = $i;
}
$data .= $palette;
}
# ... the raster data we already had ready ...
$data .= $raster;
# ... and the alpha channel we already had as well.
$data .= $alpha;
# Prepare the header which will represent this image in the
# icon file.
my $header = pack "CCCCvvV",
$w, $h, # width and height (this time the real height)
1 << $depth, # number of colours, if less than 256
0, # reserved
1, # planes
$depth, # bits per pixel
length $data; # size of real icon data
push @hdr, $header;
push @dat, $data;
}