putty/icons/macicon.py

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5.9 KiB
Python
Executable File

#!/usr/bin/env python
# Generate Mac OS X .icns files, or at least the simple subformats
# that don't involve JPEG encoding and the like.
#
# Sources: https://en.wikipedia.org/wiki/Apple_Icon_Image_format and
# some details implicitly documented by the source code of 'libicns'.
import sys
import struct
import subprocess
# The file format has a typical IFF-style (type, length, data) chunk
# structure, with one outer chunk containing subchunks for various
# different icon sizes and formats.
def make_chunk(chunkid, data):
assert len(chunkid) == 4
return chunkid + struct.pack(">I", len(data) + 8) + data
# Monochrome icons: a single chunk containing a 1 bpp image followed
# by a 1 bpp transparency mask. Both uncompressed, unless you count
# packing the bits into bytes.
def make_mono_icon(size, rgba):
assert len(rgba) == size * size
# We assume our input image was monochrome, so that the R,G,B
# channels are all the same; we want the image and then the mask,
# so we take the R channel followed by the alpha channel. However,
# we have to flip the former, because in the output format the
# image has 0=white and 1=black, while the mask has 0=transparent
# and 1=opaque.
pixels = [rgba[index][chan] ^ flip for (chan, flip) in [(0,0xFF),(3,0)]
for index in range(len(rgba))]
# Encode in 1-bit big-endian format.
data = ""
for i in range(0, len(pixels), 8):
byte = 0
for j in range(8):
if pixels[i+j] >= 0x80:
byte |= 0x80 >> j
data += chr(byte)
# This size-32 chunk id is an anomaly in what would otherwise be a
# consistent system of using {s,l,h,t} for {16,32,48,128}-pixel
# icon sizes.
chunkid = { 16: "ics#", 32: "ICN#", 48: "ich#" }[size]
return make_chunk(chunkid, data)
# Mask for full-colour icons: a chunk containing an 8 bpp alpha
# bitmap, uncompressed. The RGB data appears in a separate chunk.
def make_colour_mask(size, rgba):
assert len(rgba) == size * size
data = "".join(map(lambda pix: chr(pix[3]), rgba))
chunkid = { 16: "s8mk", 32: "l8mk", 48: "h8mk", 128: "t8mk" }[size]
return make_chunk(chunkid, data)
# Helper routine for deciding when to start and stop run-length
# encoding.
def runof3(string, position):
return (position < len(string) and
string[position:position+3] == string[position] * 3)
# RGB data for full-colour icons: a chunk containing 8 bpp red, green
# and blue images, each run-length encoded (see comment inside the
# function), and then concatenated.
def make_colour_icon(size, rgba):
assert len(rgba) == size * size
data = ""
# Mysterious extra zero header word appearing only in the size-128
# icon chunk. libicns doesn't know what it's for, and neither do
# I.
if size == 128:
data += "\0\0\0\0"
# Handle R,G,B channels in sequence. (Ignore the alpha channel; it
# goes into the separate mask chunk constructed above.)
for chan in range(3):
pixels = "".join([chr(rgba[index][chan])
for index in range(len(rgba))])
# Run-length encode each channel using the following format:
# * byte 0x80-0xFF followed by one literal byte means repeat
# that byte 3-130 times
# * byte 0x00-0x7F followed by n+1 literal bytes means emit
# those bytes once each.
pos = 0
while pos < len(pixels):
start = pos
if runof3(pixels, start):
pos += 3
pixval = pixels[start]
while (pos - start < 130 and
pos < len(pixels) and
pixels[pos] == pixval):
pos += 1
data += chr(0x80 + pos-start - 3) + pixval
else:
while (pos - start < 128 and
pos < len(pixels) and
not runof3(pixels, pos)):
pos += 1
data += chr(0x00 + pos-start - 1) + pixels[start:pos]
chunkid = { 16: "is32", 32: "il32", 48: "ih32", 128: "it32" }[size]
return make_chunk(chunkid, data)
# Load an image file from disk and turn it into a simple list of
# 4-tuples giving 8-bit R,G,B,A values for each pixel.
#
# To avoid adding any build dependency on ImageMagick or Python
# imaging libraries, none of which comes as standard on OS X, I insist
# here that the file is in RGBA .pam format (as mkicon.py will have
# generated it).
def load_rgba(filename):
with open(filename) as f:
assert f.readline() == "P7\n"
for line in iter(f.readline, ''):
words = line.rstrip("\n").split()
if words[0] == "WIDTH":
width = int(words[1])
elif words[0] == "HEIGHT":
height = int(words[1])
elif words[0] == "DEPTH":
assert int(words[1]) == 4
elif words[0] == "TUPLTYPE":
assert words[1] == "RGB_ALPHA"
elif words[0] == "ENDHDR":
break
assert width == height
data = f.read()
assert len(data) == width*height*4
rgba = [map(ord, data[i:i+4]) for i in range(0, len(data), 4)]
return width, rgba
data = ""
# Trivial argument format: each argument is a filename prefixed with
# "mono:", "colour:" or "output:". The first two indicate image files
# to use as part of the icon, and the last gives the output file name.
# Icon subformat chunks are written out in the order of the arguments.
for arg in sys.argv[1:]:
kind, filename = arg.split(":", 2)
if kind == "output":
outfile = filename
else:
size, rgba = load_rgba(filename)
if kind == "mono":
data += make_mono_icon(size, rgba)
elif kind == "colour":
data += make_colour_icon(size, rgba) + make_colour_mask(size, rgba)
else:
assert False, "bad argument '%s'" % arg
data = make_chunk("icns", data)
with open(outfile, "w") as f:
f.write(data)