2020-07-20 10:42:00

1 files changed, 0 insertions, 1341 deletions

diff --git a/tex/context/base/mkiv/lpdf-img.lua b/tex/context/base/mkiv/lpdf-img.lua
deleted file mode 100644
index fc53740f6..000000000
--- a/tex/context/base/mkiv/lpdf-img.lua
+++ /dev/null
@@ -1,1341 +0,0 @@
-if not modules then modules = { } end modules ['lpdf-img'] = {
-    version   = 1.001,
-    optimize  = true,
-    comment   = "companion to lpdf-ini.mkiv",
-    author    = "Hans Hagen, PRAGMA-ADE, Hasselt NL",
-    copyright = "PRAGMA ADE / ConTeXt Development Team",
-    license   = "see context related readme files"
-}
-
--- This started as an experiment but has potential for some (cached) optimizations.
--- At some point we can also use it for fonts. For small images performance is ok
--- with pure lua but for bigger images we can use some helpers. Normally in a
--- typesetting workflow non-interlaced images are used. One should convert
--- interlaced images to more efficient non-interlaced ones (ok, we can cache
--- them if needed).
---
--- The \LUA\ code is slightly optimized so we could have done with less lines if
--- we wanted but best gain a little. The idea is that we collect striped (in stages)
--- so that we can play with substitutions.
-
-local type = type
-local concat, move = table.concat, table.move
-local ceil, min = math.ceil, math.min
-local char, byte, find, gmatch = string.char, string.byte, string.find, string.gmatch
-local idiv = number.idiv
-local band, rshift = bit32.band, bit32.rshift
-
-local loaddata             = io.loaddata
-local setmetatableindex    = table.setmetatableindex
-local formatters           = string.formatters
-
-local streams              = utilities.streams
-local openstring           = streams.openstring
-local readstring           = streams.readstring
-local readbytetable        = streams.readbytetable
-
-local newreader            = io.newreader
-
-local tobytetable          = string.bytetable
-
-local lpdf                 = lpdf or { }
-local pdfdictionary        = lpdf.dictionary
-local pdfarray             = lpdf.array
-local pdfconstant          = lpdf.constant
-local pdfstring            = lpdf.string
-local pdfflushstreamobject = lpdf.flushstreamobject
-local pdfreference         = lpdf.reference
-local pdfverbose           = lpdf.verbose
-
-local pdfmajorversion      = lpdf.majorversion
-local pdfminorversion      = lpdf.minorversion
-
-local createimage          = images.create
-
-local zlibcompress         = (xzip or zlib).compress
-local zlibdecompress       = (xzip or zlib).decompress
-
-local trace                = false
-
-local report_jpg           = logs.reporter("graphics","jpg")
-local report_jp2           = logs.reporter("graphics","jp2")
-local report_png           = logs.reporter("graphics","png")
-
-trackers.register("graphics.backend", function(v) trace = v end)
-
-local injectors = { }
-lpdf.injectors  = injectors
-
--- todo: load from a virtual file
-
-local function loadcontent(filename,method)
-    return method == "string" and filename or loaddata(filename)
-end
-
-local function newcontent(filename,method)
-    return newreader(filename,method)
-end
-
---
-
-local chars = setmetatableindex(function(t,k) -- share this one
-    local v = (k <= 0 and "\000") or (k >= 255 and "\255") or char(k)
-    t[k] = v
-    return v
-end)
-
-do
-
-    function injectors.jpg(specification,method)
-        if specification.error then
-            return
-        end
-        local filename = specification.filename
-        if not filename then
-            return
-        end
-        local colorspace  = specification.colorspace or jpg_gray
-        local decodearray = nil
-        ----- procset     = colorspace == 0 and "image b" or "image c"
-        if colorspace == 1 then
-            colorspace = "DeviceGray"
-        elseif colorspace == 2 then
-            colorspace = "DeviceRGB"
-        elseif colorspace == 3 then
-            colorspace  = "DeviceCMYK"
-            decodearray = pdfarray { 1, 0, 1, 0, 1, 0, 1, 0 }
-        end
-        -- todo: set filename
-        local xsize      = specification.xsize
-        local ysize      = specification.ysize
-        local colordepth = specification.colordepth
-        local content    = loadcontent(filename,method)
-        local xobject    = pdfdictionary {
-            Type             = pdfconstant("XObject"),
-            Subtype          = pdfconstant("Image"),
-         -- BBox             = pdfarray { 0, 0, xsize, ysize },
-            Width            = xsize,
-            Height           = ysize,
-            BitsPerComponent = colordepth,
-            Filter           = pdfconstant("DCTDecode"),
-            ColorSpace       = pdfconstant(colorspace),
-            Decode           = decodearray,
-            Length           = #content, -- specification.length
-        } + specification.attr
-        if trace then
-            report_jpg("%s: width %i, height %i, colordepth %i, size %i",filename,xsize,ysize,colordepth,#content)
-        end
-        return createimage {
-            bbox      = { 0, 0, specification.width/xsize, specification.height/ysize }, -- mandate
-            transform = specification.transform,
-            nolength  = true,
-            nobbox    = true,
-            notype    = true,
-            stream    = content,
-            attr      = xobject(),
-        }
-    end
-
-end
-
-do
-
-    function injectors.jp2(specification,method)
-        if specification.error then
-            return
-        end
-        local filename = specification.filename
-        if not filename then
-            return
-        end
-        -- todo: set filename
-        local xsize   = specification.xsize
-        local ysize   = specification.ysize
-        local content = loadcontent(filename,method)
-        local xobject = pdfdictionary {
-            Type    = pdfconstant("XObject"),
-            Subtype = pdfconstant("Image"),
-            BBox    = pdfarray { 0, 0, xsize, ysize },
-            Width   = xsize,
-            Height  = ysize,
-            Filter  = pdfconstant("JPXDecode"),
-            Length  = #content, -- specification.length
-        } + specification.attr
-        if trace then
-            report_jp2("%s: width %i, height %i, size %i",filename,xsize,ysize,#content)
-        end
-        return createimage {
-            bbox      = { 0, 0, specification.width/xsize, specification.height/ysize }, -- mandate
-            transform = specification.transform,
-            nolength  = true,
-            nobbox    = true,
-            notype    = true,
-            stream    = content,
-            attr      = xobject(),
-        }
-    end
-
-end
-
-do
-
-    -- We don't like interlaced files. You can deinterlace them beforehand because otherwise
-    -- each run you add runtime. Actually, even masked images can best be converted to PDF
-    -- beforehand.
-
-    -- The amount of code is larger that I like and looks somewhat redundant but we sort of
-    -- optimize a few combinations that happen often.
-
-    local pngapplyfilter = pngdecode.applyfilter
-    local pngsplitmask   = pngdecode.splitmask
-    local pnginterlace   = pngdecode.interlace
-    local pngexpand      = pngdecode.expand
-    local pngtocmyk      = pngdecode.tocmyk
-
-    local filtermask, decodemask, decodestrip, transpose, expand, tocmyk
-
-    local newindex = lua.newindex
-    local newtable = lua.newtable
-
-    local function newoutput(size)
-        if newindex then
-            return newindex(size,0)
-        end
-        local t = newtable and newtable(size,0) or { }
-        for i=1,size do
-            t[i] = 0
-        end
-        return t
-    end
-
-    local function convert(t)
-        if type(t) == "table" then
-            for i=1,#t do
-                local ti = t[i]
-                if ti ~= "" then -- soon gone
-                    t[i] = chars[ti]
-                end
-            end
-            return concat(t)
-        else
-            return t
-        end
-    end
-
-    local function zero(t,k)
-        return 0
-    end
-
-    local function applyfilter(t,xsize,ysize,bpp)
-        local len = xsize * bpp + 1
-        local n   = 1
-        local m   = len - 1
-        for i=1,ysize do
-            local filter = t[n]
-            t[n] = ""
-            if filter == 0 then
-            elseif filter == 1 then
-                for j=n+bpp+1,n+m do
-                    t[j] = (t[j] + t[j-bpp]) % 256
-                end
-            elseif filter == 2 then
-                for j=n+1,n+m do
-                    t[j] = (t[j] + t[j-len]) % 256
-                end
-            elseif filter == 3 then
-                for j=n+1,n+bpp do
-                    t[j] = (t[j] + idiv(t[j-len],2)) % 256
-                end
-                for j=n+bpp+1,n+m do
-                    t[j] = (t[j] + idiv(t[j-bpp] + t[j-len],2)) % 256
-                end
-            elseif filter == 4 then
-                for j=n+1,n+bpp do
-                    local p = j - len
-                    local b = t[p]
-                    if b > 0 then
-                        t[j] = (t[j] + b) % 256
-                    end
-                end
-                for j=n+bpp+1,n+m do
-                    local p = j - len
-                    local a = t[j-bpp]
-                    local b = t[p]
-                    local c = t[p-bpp]
-                    local pa = b - c
-                    local pb = a - c
-                    local pc = pa + pb
-                    if pa < 0 then pa = - pa end
-                    if pb < 0 then pb = - pb end
-                    if pc < 0 then pc = - pc end
-                    t[j] = (t[j] + ((pa <= pb and pa <= pc and a) or (pb <= pc and b) or c)) % 256
-                end
-            end
-            n = n + len
-        end
-        return t
-    end
-
-    local filtermask_l = function (content,xsize,ysize,colordepth,colorspace,hasfilter)
-        local mask   = { }
-        local bytes  = colordepth == 16 and 2 or 1
-        local bpp    = colorspace == "DeviceRGB" and 3 or 1
-        local length = #content
-        local size   = ysize * xsize * ((bpp+1)*bytes + (hasfilter and 1 or 0))
-        local n     = 1
-        local l     = 1
-        if bytes == 2 then
-            if bpp == 1 then
-                for i=1,ysize do
-                    if hasfilter then
-                        content[n] = "" ; n = n + 1
-                    end
-                    for j=1,xsize do
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        mask[l]    = chars[content[n]] ; l = l + 1
-                        content[n] = ""                ; n = n + 1
-                        mask[l]    = chars[content[n]] ; l = l + 1
-                        content[n] = ""                ; n = n + 1
-                    end
-                end
-            elseif bpp == 3 then
-                for i=1,ysize do
-                    if hasfilter then
-                        content[n] = "" ; n = n + 1
-                    end
-                    for j=1,xsize do
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        mask[l]    = chars[content[n]] ; l = l + 1
-                        content[n] = ""                ; n = n + 1
-                        mask[l]    = chars[content[n]] ; l = l + 1
-                        content[n] = ""                ; n = n + 1
-                    end
-                end
-            else
-                return "", ""
-            end
-        else
-            if bpp == 1 then
-                for i=1,ysize do
-                    if hasfilter then
-                        content[n] = "" ; n = n + 1
-                    end
-                    for j=1,xsize do
-                        content[n] = chars[content[n]] ; n = n + 1
-                        mask[l]    = chars[content[n]] ; l = l + 1
-                        content[n] = ""                ; n = n + 1
-                    end
-                end
-            elseif bpp == 3 then
-                for i=1,ysize do
-                    if hasfilter then
-                        content[n] = "" ; n = n + 1
-                    end
-                    for j=1,xsize do
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        content[n] = chars[content[n]] ; n = n + 1
-                        mask[l]    = chars[content[n]] ; l = l + 1
-                        content[n] = ""                ; n = n + 1
-                    end
-                end
-            else
-                return "", ""
-            end
-        end
-        return concat(content), concat(mask)
-    end
-
-    local decodemask_l = function(content,xsize,ysize,colordepth,colorspace)
-        local bytes  = colordepth == 16 and 2 or 1
-        local bpp    = colorspace == "DeviceRGB" and 3 or 1
-        local slice  = bytes*(bpp+1)
-        local length = #content
-        local size   = ysize * xsize * ((bpp+1)*bytes + 1) -- assume filter
-        content = openstring(content)
-        content = readbytetable(content,length)
-        setmetatableindex(content,zero)
-        applyfilter(content,xsize,ysize,slice)
-        content, mask = filtermask(content,xsize,ysize,colordepth,colorspace,true)
-        return content, mask
-    end
-
-    local filtermask_c = function(content,xsize,ysize,colordepth,colorspace)
-        local bytes = colordepth == 16 and 2 or 1
-        local bpp   = colorspace == "DeviceRGB" and 3 or 1
-        return pngsplitmask(content,xsize,ysize,bpp,bytes)
-    end
-
-    local decodemask_c = function(content,xsize,ysize,colordepth,colorspace)
-        local mask   = true
-        local filter = false
-        local bytes  = colordepth == 16 and 2 or 1
-        local bpp    = colorspace == "DeviceRGB" and 3 or 1
-        local slice  = bytes * (bpp + 1) -- always a mask
-        content      = pngapplyfilter(content,xsize,ysize,slice)
-        return pngsplitmask(content,xsize,ysize,bpp,bytes,mask,filter)
-    end
-
-    local function decodestrip_l(s,nx,ny,slice)
-        local input = readbytetable(s,ny*(nx*slice+1))
-        setmetatableindex(input,zero)
-        applyfilter(input,nx,ny,slice)
-        return input, true
-    end
-
-    local function decodestrip_c(s,nx,ny,slice)
-        local input = readstring(s,ny*(nx*slice+1))
-        input = pngapplyfilter(input,nx,ny,slice)
-        return input, false
-    end
-
-    local xstart = { 0, 4, 0, 2, 0, 1, 0 }
-    local ystart = { 0, 0, 4, 0, 2, 0, 1 }
-    local xstep  = { 8, 8, 4, 4, 2, 2, 1 }
-    local ystep  = { 8, 8, 8, 4, 4, 2, 2 }
-
-    local xblock = { 8, 4, 4, 2, 2, 1, 1 }
-    local yblock = { 8, 8, 4, 4, 2, 2, 1 }
-
-    local function transpose_l(xsize,ysize,slice,pass,input,output,filter)
-        local xstart = xstart[pass]
-        local xstep  = xstep[pass]
-        local ystart = ystart[pass]
-        local ystep  = ystep[pass]
-        local nx     = idiv(xsize + xstep - xstart - 1,xstep)
-        local ny     = idiv(ysize + ystep - ystart - 1,ystep)
-        local offset = filter and 1 or 0
-        local xstep  = xstep * slice
-        local xstart = xstart * slice
-        local xsize  = xsize * slice
-        local target = ystart * xsize + xstart + 1
-        local ystep  = ystep * xsize
-        local start  = 1
-        local plus   = nx * xstep
-        local step   = plus - xstep
-        if not output then
-            output = newoutput(xsize*(parts or slice)*ysize)
-        end
-        if slice == 1 then
-            for j=0,ny-1 do
-                start = start + offset
-                local target = target + j * ystep
-                for target=target,target+step,xstep do
-                    output[target] = input[start]
-                    start = start + slice
-                end
-            end
-        elseif slice == 2 then
-            for j=0,ny-1 do
-                start = start + offset
-                local target = target + j * ystep
-                for target=target,target+step,xstep do
-                    output[target]   = input[start]
-                    output[target+1] = input[start+1]
-                    start = start + slice
-                end
-            end
-        elseif slice == 3 then
-            for j=0,ny-1 do
-                start = start + offset
-                local target = target + j * ystep
-                for target=target,target+step,xstep do
-                    output[target]   = input[start]
-                    output[target+1] = input[start+1]
-                    output[target+2] = input[start+2]
-                    start = start + slice
-                end
-            end
-        elseif slice == 4 then
-            for j=0,ny-1 do
-                start = start + offset
-                local target = target + j * ystep
-                for target=target,target+step,xstep do
-                    output[target]   = input[start]
-                    output[target+1] = input[start+1]
-                    output[target+2] = input[start+2]
-                    output[target+3] = input[start+3]
-                    start = start + slice
-                end
-            end
-        else
-            local delta = slice - 1
-            for j=0,ny-1 do
-                start = start + offset
-                local target = target + j * ystep
-                for target=target,target+step,xstep do
-                    move(input,start,start+delta,target,output)
-                    start = start + slice
-                end
-            end
-        end
-        return output;
-    end
-
-    local transpose_c = pnginterlace
-
- -- print(band(rshift(v,4),0x03),extract(v,4,2))
- -- print(band(rshift(v,6),0x03),extract(v,6,2))
-
-    local function expand_l(t,xsize,ysize,parts,run,factor,filter)
-        local size  = ysize * xsize + 1 -- a bit of overshoot, needs testing, probably a few bytes us ok
-        local xline = filter and (run+1) or run
-        local f     = filter and 1 or 0
-        local l     = xline - 1
-        local n     = 1
-        local o     = newoutput(size)
-        local k     = 0
-        if factor then
-            if parts == 4 then
-                for i=1,ysize do
-                    for j=n+f,n+l do
-                        local v = t[j]
-                        if v == 0 then
-                            k = k + 2
-                        else
-                            k = k + 1 ; o[k] = extract4(v,4) * 0x11
-                            k = k + 1 ; o[k] = extract4(v,0) * 0x11
-                        end
-                    end
-                    k = i * xsize
-                    n = n + xline
-                end
-            elseif parts == 2 then
-                for i=1,ysize do
-                    for j=n+f,n+l do
-                        local v = t[j]
-                        if v == 0 then
-                            k = k + 4
-                        else
-                            k = k + 1 ; o[k] = extract2(v,6) * 0x55
-                            k = k + 1 ; o[k] = extract2(v,4) * 0x55
-                            k = k + 1 ; o[k] = extract2(v,2) * 0x55
-                            k = k + 1 ; o[k] = extract2(v,0) * 0x55
-                        end
-                    end
-                    k = i * xsize
-                    n = n + xline
-                end
-            else
-                for i=1,ysize do
-                    for j=n+f,n+l do
-                        local v = t[j]
-                        if v == 0 then
-                            k = k + 8
-                        else
-                            k = k + 1 ; if band(v,0x80) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,7) * 0xFF
-                            k = k + 1 ; if band(v,0x40) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,6) * 0xFF
-                            k = k + 1 ; if band(v,0x20) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,5) * 0xFF
-                            k = k + 1 ; if band(v,0x10) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,4) * 0xFF
-                            k = k + 1 ; if band(v,0x08) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,3) * 0xFF
-                            k = k + 1 ; if band(v,0x04) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,2) * 0xFF
-                            k = k + 1 ; if band(v,0x02) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,1) * 0xFF
-                            k = k + 1 ; if band(v,0x01) ~= 0 then o[k] = 0xFF end -- o[k] = extract1(v,0) * 0xFF
-                        end
-                    end
-                    k = i * xsize
-                    n = n + xline
-                end
-            end
-        else
-            if parts == 4 then
-                for i=1,ysize do
-                    for j=n+f,n+l do
-                        local v = t[j]
-                        if v == 0 then
-                            k = k + 2
-                        else
-                            k = k + 1 ; o[k] = extract4(v,4)
-                            k = k + 1 ; o[k] = extract4(v,0)
-                        end
-                    end
-                    k = i * xsize
-                    n = n + xline
-                end
-            elseif parts == 2 then
-                for i=1,ysize do
-                    for j=n+f,n+l do
-                        local v = t[j]
-                        if v == 0 then
-                            k = k + 4
-                        else
-                            k = k + 1 ; o[k] = extract2(v,6)
-                            k = k + 1 ; o[k] = extract2(v,4)
-                            k = k + 1 ; o[k] = extract2(v,2)
-                            k = k + 1 ; o[k] = extract2(v,0)
-                        end
-                    end
-                    k = i * xsize
-                    n = n + xline
-                end
-            else
-                for i=1,ysize do
-                    for j=n+f,n+l do
-                        local v = t[j]
-                        if v == 0 then
-                            k = k + 8
-                        else
-                            k = k + 1 ; if band(v,0x80) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,7)
-                            k = k + 1 ; if band(v,0x40) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,6)
-                            k = k + 1 ; if band(v,0x20) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,5)
-                            k = k + 1 ; if band(v,0x10) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,4)
-                            k = k + 1 ; if band(v,0x08) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,3)
-                            k = k + 1 ; if band(v,0x04) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,2)
-                            k = k + 1 ; if band(v,0x02) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,1)
-                            k = k + 1 ; if band(v,0x01) ~= 0 then o[k] = 1 end -- o[k] = extract1(v,0)
-                        end
-                    end
-                    k = i * xsize
-                    n = n + xline
-                end
-            end
-        end
-        for i=size,xsize * ysize +1,-1 do
-            o[i] = nil
-        end
-        return o, false
-    end
-
-    local expand_c = pngexpand
-
-    local function analyze(colordepth,colorspace,palette,mask)
-     -- return bytes, parts, factor
-        if palette then
-            if colordepth == 16 then
-                return 2, false, false
-            elseif colordepth == 8 then
-                return 1, false, false
-            elseif colordepth == 4 then
-                return 1, 4, false
-            elseif colordepth == 2 then
-                return 1, 2, false
-            elseif colordepth == 1 then
-                return 1, 1, false
-            end
-        elseif colorspace == "DeviceGray" then
-            if colordepth == 16 then
-                return mask and 4 or 2, false, false
-            elseif colordepth == 8 then
-                return mask and 2 or 1, false, false
-            elseif colordepth == 4 then
-                return 1, 4, true
-            elseif colordepth == 2 then
-                return 1, 2, true
-            elseif colordepth == 1 then
-                return 1, 1, true
-            end
-        else
-            if colordepth == 16 then
-                return mask and 8 or 6, false, false
-            elseif colordepth == 8 then
-                return mask and 4 or 3, false, false
-            elseif colordepth == 4 then
-                return 3, 4, true
-            elseif colordepth == 2 then
-                return 3, 2, true
-            elseif colordepth == 1 then
-                return 3, 1, true
-            end
-        end
-        return false, false, false
-    end
-
-    -- 1 6 4 6 2 6 4 6
-    -- 7 7 7 7 7 7 7 7
-    -- 5 6 5 6 5 6 5 6
-    -- 7 7 7 7 7 7 7 7
-    -- 3 6 4 6 3 6 4 6
-    -- 7 7 7 7 7 7 7 7
-    -- 5 6 5 6 5 6 5 6
-    -- 7 7 7 7 7 7 7 7
-
-    local function deinterlace(content,xsize,ysize,colordepth,colorspace,palette,mask)
-        local slice, parts, factor = analyze(colordepth,colorspace,palette,mask)
-        if slice then
-            content = openstring(zlibdecompress(content))
-            local filter = false
-            local output = false
-            for pass=1,7 do
-                local xstart = xstart[pass]
-                local xstep  = xstep[pass]
-                local ystart = ystart[pass]
-                local ystep  = ystep[pass]
-                local nx     = idiv(xsize + xstep - xstart - 1,xstep)
-                local ny     = idiv(ysize + ystep - ystart - 1,ystep)
-                if nx > 0 and ny > 0 then
-                    local input, filter
-                    if parts then
-                        local nxx = ceil(nx*parts/8)
-                        input, filter = decodestrip(content,nxx,ny,slice)
-                        input, filter = expand(input,nx,ny,parts,nxx,factor,filter)
-                    else
-                        input, filter = decodestrip(content,nx,ny,slice)
-                    end
-                    output = transpose(xsize,ysize,slice,pass,input,output,filter)
-                end
-             -- if pass == 3 then
-             --     break -- still looks ok, could be nice for a preroll
-             -- end
-            end
-            return output, parts and 8 or false
-        end
-    end
-
-    -- 1 (palette used), 2 (color used), and 4 (alpha channel used)
-
-    -- paeth:
-    --
-    -- p  = a + b - c
-    -- pa = abs(p - a) => a + b - c - a => b - c
-    -- pb = abs(p - b) => a + b - c - b => a - c
-    -- pc = abs(p - c) => a + b - c - c => a + b - c - c => a - c + b - c => pa + pb
-
-    local function full(t,k) local v = "\xFF" t[k] = v return v end
-
-    local function expandvector(transparent)
-        local s = openstring(transparent)
-        local n = #transparent
-        local r = { }
-        for i=0,n-1 do
-            r[i] = readstring(s,1) -- readchar
-        end
-        setmetatableindex(r,full)
-        return r
-    end
-
-    local function createmask_l(content,palette,transparent,xsize,ysize,colordepth,colorspace)
-        if palette then
-            local r    = expandvector(transparent)
-            local size = xsize*ysize
-            local len  = ceil(xsize*colordepth/8) + 1
-            local o    = newoutput(xsize*ysize)
-            local u    = setmetatableindex(zero)
-            content    = zlibdecompress(content)
-            content    = openstring(content)
-            for i=0,ysize-1 do
-                local t = readbytetable(content,len)
-                local k = i * xsize
-                local filter = t[1]
-                if filter == 0 then
-                elseif filter == 1 then
-                    for j=3,len do
-                        t[j] = (t[j] + t[j-1]) % 256
-                    end
-                elseif filter == 2 then
-                    for j=2,len do
-                        t[j] = (t[j] + u[j]) % 256
-                    end
-                elseif filter == 3 then
-                    local j = 2
-                    t[j] = (t[j] + idiv(u[j],2)) % 256
-                    for j=3,len do
-                        t[j] = (t[j] + idiv(t[j-1] + u[j],2)) % 256
-                    end
-                elseif filter == 4 then
-                    local j = 2
-                    local p = j - len
-                    local b = t[p]
-                    if b < 0 then
-                        b = - b
-                    end
-                    if b > 0 then
-                        t[j] = (t[j] + b) % 256
-                    end
-                    for j=3,len do
-                        local p = j - len
-                        local a = t[j-1]
-                        local b = t[p]
-                        local c = t[p-1]
-                        local pa = b - c
-                        local pb = a - c
-                        local pc = pa + pb
-                        if pa < 0 then pa = - pa end
-                        if pb < 0 then pb = - pb end
-                        if pc < 0 then pc = - pc end
-                        t[j] = (t[j] + ((pa <= pb and pa <= pc and a) or (pb <= pc and b) or c)) % 256
-                    end
-                end
-                if colordepth == 8 then
-                    for j=2,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[v]
-                    end
-                elseif colordepth == 4 then
-                    for j=2,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[extract4(v,4)]
-                        k = k + 1 ; o[k] = r[extract4(v,0)]
-                    end
-                elseif colordepth == 2 then
-                    for j=2,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[extract2(v,6)]
-                        k = k + 1 ; o[k] = r[extract2(v,4)]
-                        k = k + 1 ; o[k] = r[extract2(v,2)]
-                        k = k + 1 ; o[k] = r[extract2(v,0)]
-                    end
-                else
-                    for j=2,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[extract1(v,7)]
-                        k = k + 1 ; o[k] = r[extract1(v,6)]
-                        k = k + 1 ; o[k] = r[extract1(v,5)]
-                        k = k + 1 ; o[k] = r[extract1(v,4)]
-                        k = k + 1 ; o[k] = r[extract1(v,3)]
-                        k = k + 1 ; o[k] = r[extract1(v,2)]
-                        k = k + 1 ; o[k] = r[extract1(v,1)]
-                        k = k + 1 ; o[k] = r[extract1(v,0)]
-                    end
-                end
-                u = t
-            end
-            return concat(o,"",1,size)
-        end
-    end
-
-    local function createmask_c(content,palette,transparent,xsize,ysize,colordepth,colorspace)
-        if palette then
-            local r    = expandvector(transparent)
-            local size = xsize*ysize
-            local len  = ceil(xsize*colordepth/8)
-            local o    = newoutput(size)
-            content    = zlibdecompress(content)
-            content    = pngapplyfilter(content,len,ysize,1) -- nostrip (saves copy)
-            content    = openstring(content)
-            for i=0,ysize-1 do
-                local t = readbytetable(content,len)
-                local k = i * xsize
-                if colordepth == 8 then
-                    for j=1,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[v]
-                    end
-                elseif colordepth == 4 then
-                    for j=1,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[extract4(v,4)]
-                        k = k + 1 ; o[k] = r[extract4(v,0)]
-                    end
-                elseif colordepth == 2 then
-                    for j=1,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[extract2(v,6)]
-                        k = k + 1 ; o[k] = r[extract2(v,4)]
-                        k = k + 1 ; o[k] = r[extract2(v,2)]
-                        k = k + 1 ; o[k] = r[extract2(v,0)]
-                    end
-                else
-                    for j=1,len do
-                        local v = t[j]
-                        k = k + 1 ; o[k] = r[extract1(v,7)]
-                        k = k + 1 ; o[k] = r[extract1(v,6)]
-                        k = k + 1 ; o[k] = r[extract1(v,5)]
-                        k = k + 1 ; o[k] = r[extract1(v,4)]
-                        k = k + 1 ; o[k] = r[extract1(v,3)]
-                        k = k + 1 ; o[k] = r[extract1(v,2)]
-                        k = k + 1 ; o[k] = r[extract1(v,1)]
-                        k = k + 1 ; o[k] = r[extract1(v,0)]
-                    end
-                end
-            end
-            return concat(o,"",1,size)
-        end
-    end
-
-    local function tocmyk_l(content,colordepth)
-        local l = #content
-        local t = { }
-        local n = 0
-        if colordepth == 8 then
-            for i=1,l,3 do
-                local r, g, b = byte(content,i,i+2)
-                n = n + 1 ; t[n] = char(255-r,255-g,255-b,0) -- a tad faster than chars[...]
-            end
-        else
-            for i=1,l,6 do
-                local r1, r2, g1, g2, b1, b2 = byte(content,i,i+5)
-                n = n + 1 ; t[n] = char(255-r1,255-r2,255-g1,255-g2,255-b1,255-b2,0,0)
-            end
-        end
-        return concat(t)
-    end
-
-    local tocmyk_c = pngtocmyk or tocmyk_l
-
-    local function converttocmyk(content,colorspace,colordepth)
-        if colorspace == "DeviceRGB" and colordepth == 8 or colordepth == 16 then
-            local done = tocmyk(content,colordepth)
-            if done then
-                content    = done
-                colorspace = "DeviceCMYK"
-            end
-        end
-        return content, colorspace
-    end
-
-    local function switch(v)
-        if v then
-            filtermask  = filtermask_l
-            decodemask  = decodemask_l
-            decodestrip = decodestrip_l
-            transpose   = transpose_l
-            expand      = expand_l
-            createmask  = createmask_l
-            tocmyk      = tocmyk_l
-        else
-            filtermask  = filtermask_c
-            decodemask  = decodemask_c
-            decodestrip = decodestrip_c
-            transpose   = transpose_c
-            expand      = expand_c
-            createmask  = createmask_c
-            tocmyk      = tocmyk_c
-        end
-    end
-
-    if pngapplyfilter then
-        switch(false)
-        directives.register("graphics.png.purelua",switch)
-    else
-        switch(true)
-    end
-
-    local alwaysdecode  = false -- trucky with palettes
-    local compresslevel = 3
-
-    directives.register("graphics.png.recompress", function(v)
-        alwaysdecode = v
-    end)
-
-    directives.register("graphics.png.compresslevel", function(v)
-        v = tonumber(v)
-        if compresslevel >= 0 or compresslevel <= 9 then
-            compresslevel = v
-        end
-    end)
-
-    function injectors.png(specification,method) -- todo: method in specification
-        if specification.error then
-            return
-        end
-        local filename = specification.filename
-        if not filename then
-            return
-        end
-        local colorspace = specification.colorspace
-        if not colorspace then
-            return
-        end
-        local interlace = specification.interlace or 0
-        if interlace == 1 then
-            interlace = true
-        elseif interlace == 0 then
-            interlace = false
-        else
-            report_png("unknown interlacing %i",interlace)
-            return
-        end
-        local tables = specification.tables
-        if not tables then
-            return
-        end
-        local idat = tables.idat
-        if not idat then
-            return
-        end
-        local pngfile = newcontent(filename,method)
-        if not pngfile then
-            return
-        end
-        local content = idat(pngfile,true)
-        tables.idat = false
-        --
-     -- if tables.gama then
-     --     report_png("ignoring gamma correction")
-     -- end
-        --
-        local xsize       = specification.xsize
-        local ysize       = specification.ysize
-        local colordepth  = specification.colordepth or 8
-        local mask        = false
-        local transparent = false
-        local palette     = false
-        local enforcecmyk = specification.enforcecmyk
-        local colors      = 1
-        if     colorspace == 0 then    -- gray | image b
-            colorspace  = "DeviceGray"
-            transparent = true
-        elseif colorspace == 2 then    -- rgb | image c
-            colorspace  = "DeviceRGB"
-            colors      = 3
-            transparent = true
-        elseif colorspace == 3 then    -- palette | image c+i
-            colorspace  = "DeviceRGB"
-            palette     = true
-            transparent = true
-        elseif colorspace == 4 then    -- gray | alpha | image b
-            colorspace = "DeviceGray"
-            mask       = true
-        elseif colorspace == 6 then    -- rgb | alpha | image c
-            colorspace = "DeviceRGB"
-            colors     = 3
-            mask       = true
-        else
-            report_png("unknown colorspace %i",colorspace)
-            return
-        end
-        --
-        if transparent then
-            local trns = tables.trns
-            if trns then
-                transparent = trns(pngfile,true)
-                if transparent == "" then
-                    transparent = false
-                end
-                tables.trns = false
-            else
-                transparent = false
-            end
-        end
-        --
-        local decode = alwaysdecode -- tricky, might go away
-        local filter = pdfconstant("FlateDecode")
-        local major  = pdfmajorversion()
-        local minor  = pdfminorversion()
-        if major > 1 then
-            -- we're okay
-        elseif minor < 5 and colordepth == 16 then
-            report_png("16 bit colordepth not supported in pdf < 1.5")
-            return
-        elseif minor < 4 and (mask or transparent) then
-            report_png("alpha channels not supported in pdf < 1.4")
-            return
-        elseif minor < 2 then
-            report_png("you'd better use a version > 1.2")
-            return
-         -- decode = true
-        end
-        --
-        -- todo: compresslevel (or delegate)
-        --
-        if palette then
-            local plte = tables.plte
-            if plte then
-                palette = plte(pngfile,true)
-                if palette == "" then
-                    palette = false
-                end
-                tables.plte = false
-            else
-                palette = false
-            end
-        end
-        --
-        if interlace then
-            local r, p = deinterlace(content,xsize,ysize,colordepth,colorspace,palette,mask)
-            if not r then
-                return
-            end
-            if p then
-                colordepth = p
-            end
-            if mask then
-                if not (colordepth == 8 or colordepth == 16) then
-                    report_png("mask can't be split from the image")
-                    return
-                end -- get rid of bpp:
-                content, mask = filtermask(r,xsize,ysize,colordepth,colorspace,false)
-            else
-                content = convert(r) -- can be in deinterlace if needed
-            end
-            if enforcecmyk then
-                content, colorspace = converttocmyk(content,colorspace,colordepth)
-            end
-            if compresslevel > 0 then
-                content = zlibcompress(content,compresslevel)
-            else
-                filter = nil
-            end
-            decode = true
-        elseif mask then
-            if not (colordepth == 8 or colordepth == 16) then
-                report_png("mask can't be split from the image")
-                return
-            end
-            content = zlibdecompress(content)
-            content, mask = decodemask(content,xsize,ysize,colordepth,colorspace)
-            if enforcecmyk and not palette then
-                content, colorspace = converttocmyk(content,colorspace,colordepth)
-            end
-            if compresslevel > 0 then
-                content = zlibcompress(content,compresslevel)
-            else
-                filter = nil
-            end
-            decode  = true -- we don't copy the filter byte
-        elseif transparent then
-            -- in test suite
-            -- how about decode/recompress here
-            if palette then
-                mask = createmask(content,palette,transparent,xsize,ysize,colordepth,colorspace)
-            else
-                pallette = false
-            end
-        elseif decode or (enforcecmyk and not palette) then
-            -- this one needs checking
-            local bytes = analyze(colordepth,colorspace)
-            if bytes then
-                content = zlibdecompress(content)
-                content = decodestrip(openstring(content),xsize,ysize,bytes)
-                if enforcecmyk and not palette then
-                    content, colorspace = converttocmyk(content,colorspace,colordepth)
-                end
-                if compresslevel > 0 then
-                    content = zlibcompress(content,compresslevel)
-                else
-                    filter = nil
-                end
-            else
-                return
-            end
-            decode = true -- due to enforcecmyk
-        else
-         -- print("PASS ON")
-        end
-        if palette then
-            local colorspace = "DeviceRGB"
-            local nofbytes   = 3
-            if enforcecmyk then
-                palette    = converttocmyk(palette,colorspace,8)
-                colorspace = "DeviceCMYK"
-                nofbytes   = 4
-            end
-            palette = pdfarray {
-                pdfconstant("Indexed"),
-                pdfconstant(colorspace),
-                idiv(#palette,nofbytes),
-                pdfreference(pdfflushstreamobject(palette)),
-            }
-        end
-        pngfile:close()
-        local xobject = pdfdictionary {
-            Type             = pdfconstant("XObject"),
-            Subtype          = pdfconstant("Image"),
-         -- BBox             = pdfarray { 0, 0, xsize, ysize },
-            Width            = xsize,
-            Height           = ysize,
-            BitsPerComponent = colordepth,
-            Filter           = filter,
-            ColorSpace       = palette or pdfconstant(colorspace),
-            Length           = #content,
-        } + specification.attr
-        if mask then
-            local d = pdfdictionary {
-                Type             = pdfconstant("XObject"),
-                Subtype          = pdfconstant("Image"),
-                Width            = xsize,
-                Height           = ysize,
-                BitsPerComponent = palette and 8 or colordepth,
-                ColorSpace       = pdfconstant("DeviceGray"),
-            }
-            xobject.SMask = pdfreference(pdfflushstreamobject(mask,d()))
-        end
-        if not decode then
-            xobject.DecodeParms  = pdfdictionary {
-                Colors           = colors,
-                Columns          = xsize,
-                BitsPerComponent = colordepth,
-                Predictor        = 15,
-            }
-        end
-        if trace then
-            report_png("%s: width %i, height %i, colordepth %i, size %i, palette %l, mask %l, transparent %l, decode %l",filename,xsize,ysize,colordepth,#content,palette,mask,transparent,decode)
-        end
-        if specification.colorref then
-            xobject.ColorSpace = pdfreference(specification.colorref)
-        end
-        local width  = specification.width  or xsize * 65536
-        local height = specification.height or ysize * 65536
-        return createimage {
-            bbox      = { 0, 0, width/xsize, height/ysize }, -- mandate
-            transform = specification.transform,
-            nolength  = true,
-            nobbox    = true,
-            notype    = true,
-            stream    = content,
-            attr      = xobject(),
-        }
-    end
-
-end
-
-do
-
-    local function pack(specification,what)
-        local t = { }
-        local n = 0
-        local s = specification.colorspace
-        local d = specification.data
-        local x = specification.xsize
-        local y = specification.ysize
-        if what == "mask" then
-            d = specification.mask
-            s = 1
-        elseif what == "indexed" then
-            s = 1
-        elseif what == "index" then
-            d = specification.index
-            s = - s
-        end
-        if s > 0 then
-            if s == 1 then
-                for i=1,y do
-                    local r = d[i]
-                    for j=1,x do
-                        n = n + 1 ; t[n] = chars[r[j]]
-                    end
-                end
-            elseif s == 2 then
-                for i=1,y do
-                    local r = d[i]
-                    for j=1,x do
-                        local c = r[j]
-                        n = n + 1 ; t[n] = chars[c[1]]
-                        n = n + 1 ; t[n] = chars[c[2]]
-                        n = n + 1 ; t[n] = chars[c[3]]
-                     -- n = n + 1 ; t[n] = char(c[1],c[2],c[3]) -- test this
-                    end
-                end
-            elseif s == 3 then
-                for i=1,y do
-                    local r = d[i]
-                    for j=1,x do
-                        local c = r[j]
-                        n = n + 1 ; t[n] = chars[c[1]]
-                        n = n + 1 ; t[n] = chars[c[2]]
-                        n = n + 1 ; t[n] = chars[c[3]]
-                        n = n + 1 ; t[n] = chars[c[4]]
-                     -- n = n + 1 ; t[n] = char(c[1],c[2],c[3],c[4]) -- test this
-                    end
-                end
-            end
-            return concat(t)
-        else
-            local z = d[0] and 0 or 1
-            if s == -1 then
-                local f = formatters["%02X"]
-                for i=z,#d do
-                    n = n + 1 ; t[n] = f(d[i])
-                end
-            elseif s == -2 then
-                local f = formatters["%02X%02X%02X"]
-                for i=z,#d do
-                    local c = d[i]
-                    n = n + 1 ; t[n] = f(c[1],c[2],c[3])
-                end
-            elseif s == -3 then
-                local f = formatters["%02X%02X%02X%02X"]
-                for i=z,#d do
-                    local c = d[i]
-                    n = n + 1 ; t[n] = f(c[1],c[2],c[3],c[4])
-                end
-            end
-            return "<" .. concat(t," ") .. ">"
-        end
-        return ""
-    end
-
-    function injectors.bitmap(specification)
-        local data = specification.data
-        if not data then
-            return
-        end
-        local xsize = specification.xsize or 0
-        local ysize = specification.ysize or 0
-        if xsize == 0 or ysize == 0 then
-            return
-        end
-        local colorspace = specification.colorspace or 1
-        if colorspace == 1 then
-            colorspace = "DeviceGray"
-        elseif colorspace == 2 then
-            colorspace = "DeviceRGB"
-        elseif colorspace == 3 then
-            colorspace  = "DeviceCMYK"
-        end
-        local colordepth = (specification.colordepth or 2) == 16 or 8
-        local index      = specification.index
-        local content    = pack(specification,index and "indexed" or "data")
-        local mask       = specification.mask
-        local colorspace = pdfconstant(colorspace)
-        if index then
-            colorspace = pdfarray {
-                pdfconstant("Indexed"),
-                colorspace,
-                #index + (index[0] and 0 or -1), -- upper index
-                pdfverbose(pack(specification,"index"))
-            }
-        end
-        local xobject    = pdfdictionary {
-            Type             = pdfconstant("XObject"),
-            Subtype          = pdfconstant("Image"),
-            BBox             = pdfarray { 0, 0, xsize, ysize },
-            Width            = xsize,
-            Height           = ysize,
-            BitsPerComponent = colordepth,
-            ColorSpace       = colorspace,
-            Length           = #content, -- specification.length
-        }
-        if mask then
-            local d = pdfdictionary {
-                Type             = pdfconstant("XObject"),
-                Subtype          = pdfconstant("Image"),
-                Width            = xsize,
-                Height           = ysize,
-                BitsPerComponent = colordepth,
-                ColorSpace       = pdfconstant("DeviceGray"),
-            }
-            xobject.SMask = pdfreference(pdfflushstreamobject(pack(specification,"mask"),d()))
-        end
-        return createimage {
-            bbox     = { 0, 0, specification.width/xsize, specification.height/ysize }, -- mandate
-         -- nolength = true,
-            nobbox   = true,
-            notype   = true,
-            stream   = content,
-            attr     = xobject(),
-        }
-    end
-
-    backends.pdf.codeinjections.bitmap = injectors.bitmap
-
-end
-
--- local function validcompression(data)
---     local d  = utilities.streams.openstring(data)
---     local b1 = utilities.streams.readbyte(d)
---     local b2 = utilities.streams.readbyte(d)
---     print(b1,b2)
---     if (b1 * 256 + b2) % 31 ~= 0 then
---         return false, "no zlib compressed file"
---     end
---     local method = band(b1,15)
---     if method ~= 8 then
---         return false, "method 8 expected"
---     end
---     local detail = band(rshift(b1,4),15)
---     if detail > 7 then
---         return false, "window 32 expected"
---     end
---     local preset = band(rshift(b2,5),1)
---     if preset ~= 0 then
---         return false, "unexpected preset dictionary"
---     end
---     return true
--- end