#!/usr/bin/perl
-# Take nine input image files and convert them into a
-# multi-resolution Windows .ICO icon file. The nine files should
-# be, in order:
+# Take a collection of input image files and convert them into a
+# multi-resolution Windows .ICO icon file.
#
-# - 48x48 icons at 24-bit, 8-bit and 4-bit colour depth respectively
-# - 32x32 icons at 24-bit, 8-bit and 4-bit colour depth respectively
-# - 16x16 icons at 24-bit, 8-bit and 4-bit colour depth respectively
+# The input images can be treated as having four different colour
+# depths:
#
-# ICO files support a 1-bit alpha channel on all these image types.
+# - 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.
#
-# TODO: it would be nice if we could extend this icon builder to
-# support monochrome icons and a user-specified subset of the
-# available formats. None of that should be too hard: the
-# monochrome raster data has the same format as the alpha channel,
-# monochrome images have a 2-colour palette containing 000000 and
-# FFFFFF respectively, and really the biggest problem is designing
-# a sensible command-line syntax!
+# 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,
);
@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 = ();
-&readicon($ARGV[0], 48, 48, 24);
-&readicon($ARGV[1], 48, 48, 8);
-&readicon($ARGV[2], 48, 48, 4);
-&readicon($ARGV[3], 32, 32, 24);
-&readicon($ARGV[4], 32, 32, 8);
-&readicon($ARGV[5], 32, 32, 4);
-&readicon($ARGV[6], 16, 16, 24);
-&readicon($ARGV[7], 16, 16, 8);
-&readicon($ARGV[8], 16, 16, 4);
+$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
sub readicon {
my $filename = shift @_;
- my $w = shift @_;
- my $h = 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).
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.
- my $currbyte = 0, $currbits = 0;
- for ($i = 0; $i < scalar @$data; $i++) {
- $pix = $data->[$i];
- $currbyte <<= $depth;
- $currbits += $depth;
- if (defined $pix) {
- if (!defined $pal{$pix}) {
- die "illegal colour value $pix at pixel $i in $filename\n";
+ $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;
}
- $currbyte |= $pal{$pix};
- } else {
- $currbyte |= 0;
- }
- if ($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];
~mdw / sgt / puzzles / blobdiff