luametalatex/luametalatex-pdf-image-png.lua

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local function ignore() end
local parse = setmetatable({
-- IHDR = below,
-- PLTE = below,
-- IDAT = below,
-- IEND = below,
-- I'm not yet sure what to do about the following four color management chunks:
-- These two will probably be ignored (if you care about this stuff, you probably
-- prefer an ICC profile anyway. Also especially cHRM requires some weird computations.)
-- cHRM = TODO, -- ignore?
-- gAMA = TODO, -- ignore?
-- iCCP is implemented, but profiles are not cached, so it might include the
-- same profile many times
-- iCCP = below,
-- I would expect sRGB to be the most common, but it is a bit complicated because
-- PDF seems to require us to ship an actual ICC profile to support sRGB. Maybe later.
-- sRGB = TODO,
sBIT = ignore,
bKGD = ignore, -- Background color. Ignored since we support transparency
hIST = ignore, -- Color histogram
-- tRNS = below,
-- pHYs = below, -- resolution information
sPLT = ignore, -- Suggested palette but we support full truetype
tIME = ignore, -- The following only store metadata
iTXt = ignore,
tEXt = ignore,
zTXt = ignore,
}, {
__index = function(_, n)
print("Table " .. n .. " unsupported") -- FIXME: Handle extensions by detecing if they are critical etc.
return ignore
end
})
function parse.IHDR(buf, i, after, ctxt)
if next(ctxt) then
error[[The header should come first]]
end
local compression, filter
ctxt.width, ctxt.height,
ctxt.bitdepth, ctxt.colortype,
compression, filter,
ctxt.interlace, i = string.unpack(">I4I4I1I1I1I1I1", buf, i)
if i ~= after then
return [[Invalid header size]]
end
if compression ~= 0 then
error [[Unsupported compression mode]]
end
if filter ~= 0 then
error [[Unsupported filter mode]]
end
end
function parse.PLTE(buf, i, after, ctxt)
if ctxt.PLTE then
error[[Multiple palettes detected]]
end
if (after-i)%3 ~= 0 then
error[[Invalid palette lenght]]
end
ctxt.PLTE_len = (after-i) // 3
ctxt.PLTE = string.sub(buf, i, after-1)
end
function parse.tRNS(buf, i, after, ctxt)
if ctxt.colortype == 3 then
local count = assert(ctxt.PLTE_len)
local patt = lpeg.P(1) * lpeg.Cc'\xff'
for j=0,after-i-1 do
local off = i+j
patt = lpeg.P(string.char(j)) * lpeg.Cc(buf:sub(off, off)) + patt
end
ctxt.tRNS = lpeg.Cs(lpeg.Cg(patt)^0)
elseif ctxt.colortype == 0 then
local color
color, i = string.unpack(">I2", buf, i)
assert(i == after)
ctxt.tRNS = string.format('%i %i', color, color)
elseif ctxt.colortype == 2 then
local r, g, b
r, g, b, i = string.unpack(">I2I2I2", buf, i)
assert(i == after)
ctxt.tRNS = string.format('%i %i %i %i %i %i', r, r, g, g, b, b)
end
end
local meterperinch = 0.0254
function parse.pHYs(buf, i, after, ctxt)
local xres, yres, unit
xres, yres, unit, i = string.unpack('>I4I4I1', buf, i)
if unit == 0 then
if xres > yres then
ctxt.xres, ctxt.yres = xres/yres, 0
elseif xres < yres then
ctxt.xres, ctxt.yres = 0, yres/xres
end
elseif unit == 1 then
ctxt.xres, ctxt.yres = xres * meterperinch, yres * meterperinch
else
error[[Invalid unit]]
end
assert(i == after)
end
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function parse.sRGB(buf, i, after, ctxt)
assert(i+1 == after)
ctxt.sRGB = buf:char(i)
end
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function parse.iCCP(buf, i, after, ctxt)
local j = buf:find('\0', i, true)
assert(j+1<after)
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-- local name = buf:sub(i, j-1)
-- print('ICC Profile name: ' .. name)
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assert(buf:byte(j+1) == 0) -- The only known compression mode
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ctxt.iCCP = buf:sub(j+2, after-1)
-- ctxt.iCCP = xzip.decompress(buf:sub(j+2, after-1))
end
function parse.gAMA(buf, i, after, ctxt)
local gamma, i = string.unpack(">I4", buf, i)
assert(after == i)
ctxt.gAMA = 100000/gamma
end
function parse.cHRM(buf, i, after, ctxt)
local x_W, y_W, x_R, y_R, x_G, y_G, x_B, y_B, i = string.unpack(">I4I4I4I4I4I4I4I4", buf, i)
assert(after == i)
x_W, y_W, x_R, y_R, x_G, y_G, x_B, y_B = x_W/100000, y_W/100000, x_R/100000, y_R/100000,
x_G/100000, y_G/100000, x_B/100000, y_B/100000
local z = y_W*((x_G-x_B)*y_R-(x_R-x_B)*y_G+(x_R-x_G)*y_B)
z = 1/z
local Y_A = y_R*((x_G-x_B)*y_W-(x_W-x_B)*y_G+(x_W-x_G)*y_B) * z
local X_A, Z_A = Y_A*x_R/y_R, Y_A*((1-x_R)/y_R-1)
local Y_B = -y_G*((x_R-x_B)*y_W-(x_W-x_B)*y_R+(x_W-x_R)*y_B) * z
local X_B, Z_B = Y_B*x_G/y_G, Y_B*((1-x_G)/y_G-1)
local Y_C = y_B*((x_R-x_G)*y_W-(x_W-x_G)*y_R+(x_W-x_R)*y_G) * z
local X_C, Z_C = Y_C*x_B/y_B, Y_C*((1-x_B)/y_B-1)
local X_W, Y_W, Z_W = X_A+X_B+X_C, Y_A+Y_B+Y_C, Z_A+Z_B+Z_C
ctxt.cHRM = string.format("/WhitePoint[%f %f %f]/Matrix[%f %f %f %f %f %f %f %f %f]",
X_W, Y_W, Z_W,
X_A, Y_A, Z_A,
X_B, Y_B, Z_B,
X_C, Y_C, Z_C)
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end
function parse.IDAT(buf, i, after, ctxt)
ctxt.IDAT = ctxt.IDAT or {}
table.insert(ctxt.IDAT, buf:sub(i, after-1))
end
function parse.IEND(buf, i, after)
if i ~= after then
error[[Unexpected data in end chunk]]
end
end
local function run(buf, i, len, limit)
i = i or 1
len = i+(len or #buf)
if buf:sub(i,i+7) ~= "\x89PNG\x0D\x0A\x1A\x0A" then
error[[You lied. This isn't a PNG file.]]
end
i = i+8
local chunks = {}
while i < len do
local length, tp, off = string.unpack(">I4c4", buf, i)
if tp == limit then break end
parse[tp](buf, off, off + length, chunks)
i = off + length + 4
end
return chunks, i
end
local function passes(buf, width, height, bitdepth, colortype)
local stride = (bitdepth == 16 and 2 or 1) * (1 + (colortype&3 == 2 and 2 or 0) + (colortype&4)/4)
local passes = {
{(width+7)//8, (height+7)//8},
{(width+3)//8, (height+7)//8},
{(width+3)//4, (height+3)//8},
{(width+1)//4, (height+3)//4},
{(width+1)//2, (height+1)//4},
{ width //2, (height+1)//2},
{ width , height //2},
}
local off = 1
local result
for i=1,#passes do
local xsize, ysize = passes[i][1], passes[i][2]
if xsize ~= 0 and ysize ~= 0 then
if bitdepth < 8 then
xsize = (xsize * bitdepth + 7) // 8
end
local after = off + (xsize+1) * stride * ysize
local pass = pngdecode.applyfilter(
buf:sub(off, after-1),
xsize,
ysize,
stride)
if bitdepth < 8 then
pass = pngdecode.expand(pass, passes[i][1], ysize, bitdepth, xsize)
end
result = pngdecode.interlace(width, height, stride, i, pass, result)
off = after
end
end
assert(off == #buf+1)
return result
end
local png_functions = {}
function png_functions.scan(img)
local file = io.open(img.filepath)
if not file then
error[[PDF image could not be opened.]]
end
local buf = file:read'a'
file:close()
local t = run(buf, 1, #buf, 'IDAT')
img.pages = 1
img.page = 1
img.rotation = 0
img.xsize, img.ysize = t.width, t.height
img.xres, img.yres = t.xres or 0, t.yres or 0
img.colordepth = t.bitdepth
end
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local srgb_colorspace
local intents = {[0]=
'/Intent/Perceptual',
'/Intent/RelativeColorimetric',
'/Intent/Saturation',
'/Intent/AbsoluteColorimetric',
}
local function srgb_lookup(pfile, intent)
if not srgb_colorspace then
local f = io.open(kpse.find_file'sRGB.icc.zlib')
local profile = f:read'a'
f:close()
local objnum = pfile:stream(nil, '/Filter/FlateDecode/N ' .. tostring(colortype & 2 == 2 and '3' or '1'), t.iCCP, nil, true)
srgb_colorspace = string.format('[/ICCBased %i 0 R]', objnum)
end
return objnum, intents[intent] or ''
end
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local pdf_escape = require'luametalatex-pdf-escape'.escape_bytes
local function rawimage(t, content)
content = xzip.decompress(content)
if t.interlace == 1 then
content = passes(content, t.width, t.height, t.bitdepth, t.colortype)
else
local xsize = t.width
if t.bitdepth < 8 then
xsize = (xsize * t.bitdepth + 7) // 8
end
local colortype = t.colortype
content = pngdecode.applyfilter(
content,
xsize,
t.height,
(t.bitdepth == 16 and 2 or 1) * (1 + (colortype&3 == 2 and 2 or 0) + (colortype&4)/4))
end
return content
end
function png_functions.write(pfile, img)
local file = io.open(img.filepath)
if not file then
error[[PDF image could not be opened.]]
end
local buf = file:read'a'
file:close()
local t = run(buf, 1, #buf, 'IEND')
local colorspace
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local intent = ''
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local colortype = t.colortype
if img.colorspace then
colorspace = string.format(' %i 0 R', img.colorspace)
elseif t.iCCP then
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local icc_ref = pfile:stream(nil, '/Filter/FlateDecode/N ' .. tostring(colortype & 2 == 2 and '3' or '1'), t.iCCP, nil, true)
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colorspace = string.format('[/ICCBased %i 0 R]', icc_ref)
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elseif t.sRGB then
colorspace, intent = srgb_lookup(pfile, t.sRGB)
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elseif colortype & 2 == 2 then -- RGB
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if t.cHRM then
local gamma = t.gAMA or 2.2
gamma = gamma and string.format("/Gamma[%f %f %f]", gamma, gamma, gamma) or ''
colorspace = string.format("[/CalRGB<<%s%s>>]", t.cHRM, gamma)
else
if t.gAMA then
texio.write_nl'Warning: (PNG) Gamma correction without chromaticity information is unsupported. Gamma value will be ignored.'
end
colorspace = '/DeviceRGB'
end
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else -- Gray
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if t.gAMA or t.cHRM then
texio.write_nl'Warning: (PNG) Gamma correction and chromaticity specifications are only supported for RGB images.'
end
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colorspace = '/DeviceGray'
end
if colortype & 1 == 1 then -- Indexed
colorspace = string.format('[/Indexed%s %i%s]', colorspace, t.PLTE_len-1, pdf_escape(t.PLTE))
end
local colordepth = t.interlace == 1 and 8 or img.colordepth
local dict = string.format("/Subtype/Image/Width %i/Height %i/BitsPerComponent %i/ColorSpace%s", img.xsize, img.ysize, colordepth, colorspace)
local content = table.concat(t.IDAT)
local copy -- = true
if copy and (t.interlace == 1 or colortype & 4 == 4) then -- TODO: Add additional conditions
copy = false
end
if copy then
-- In this case we never have to deal with an alpha component
dict = string.format(
'%s/Filter/FlateDecode/DecodeParms<</Colors %i/Columns %i/BitsPerComponent %i/Predictor 10>>',
dict, colortype == 2 and 3 or 1, img.xsize, colordepth)
else
content = rawimage(t, content)
if colortype & 4 == 4 then -- Alpha channel present
local mask
content, mask = pngdecode.splitmask(
content,
img.xsize,
img.ysize,
1 + (colortype&2),
colordepth//8) -- colordepth must be 8 or 16 if alpha is present
local mask_dict = string.format("/Subtype/Image/Width %i/Height %i/BitsPerComponent %i/ColorSpace/DeviceGray", img.xsize, img.ysize, colordepth)
local objnum = pfile:stream(nil, mask_dict, mask)
dict = string.format('%s/SMask %i 0 R', dict, objnum)
end
end
if t.tRNS then
if colortype == 3 then
local unpacked = copy and rawimage(t, content) or content
if colordepth ~= 8 then
unpacked = pngdecode.expand(unpacked, img.xsize, img.ysize, colordepth, (img.xsize*colordepth+7)//8)
end
unpacked = t.tRNS:match(unpacked)
local mask_dict = string.format("/Subtype/Image/Width %i/Height %i/BitsPerComponent 8/ColorSpace/DeviceGray", img.xsize, img.ysize)
local objnum = pfile:stream(nil, mask_dict, unpacked)
dict = string.format('%s/SMask %i 0 R', dict, objnum)
else
dict = string.format('%s/Mask[%s]', dict, t.tRNS)
end
end
local attr = img.attr
if attr then
dict = dict .. attr
end
pfile:stream(img.objnum, dict, content, nil, copy)
end
return png_functions