if not modules then modules = { } end modules ['lpdf-grp'] = {
    version   = 1.001,
    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"
}

local type, tonumber = type, tonumber
local formatters, gsub = string.formatters, string.gsub
local concat, sort = table.concat, table.sort
local round = math.round

local colors         = attributes.colors
local basepoints     = number.dimenfactors.bp

local pdfbackend     = backends.registered.pdf
local nodeinjections = pdfbackend.nodeinjections
local codeinjections = pdfbackend.codeinjections
local registrations  = pdfbackend.registrations

local lpdf           = lpdf
local pdfdictionary  = lpdf.dictionary
local pdfarray       = lpdf.array
local pdfconstant    = lpdf.constant
local pdfboolean     = lpdf.boolean
local pdfreference   = lpdf.reference
local pdfflushobject = lpdf.flushobject

local createimage    = images.create
local wrapimage      = images.wrap
local embedimage     = images.embed

-- can also be done indirectly:
--
-- 12 : << /AntiAlias false /ColorSpace  8 0 R /Coords [ 0.0 0.0 1.0 0.0 ] /Domain [ 0.0 1.0 ] /Extend [ true true ] /Function 22 0 R /ShadingType 2 >>
-- 22 : << /Bounds [ ] /Domain [ 0.0 1.0 ] /Encode [ 0.0 1.0 ] /FunctionType 3 /Functions [ 31 0 R ] >>
-- 31 : << /C0 [ 1.0 0.0 ] /C1 [ 0.0 1.0 ] /Domain [ 0.0 1.0 ] /FunctionType 2 /N 1.0 >>

local function shade(stype,name,domain,color_a,color_b,n,colorspace,coordinates,separation,steps,fractions)
    local func = nil
    --
    -- domain has to be consistently added in all dictionaries here otherwise
    -- acrobat fails with a drawing error
    --
    domain = pdfarray(domain)
    n      = tonumber(n)
    --
    if steps then
        local list   = pdfarray()
        local bounds = pdfarray()
        local encode = pdfarray()
        -- The bounds need to be sorted and we can have illustrator output
        -- that violates this rule.
        local tmp = { }
        for i=1,steps do
            tmp[i] = { fractions[i], color_a[i], color_b[i] }
        end
        sort(tmp, function(a,b)
            return a[1] < b[1]
        end)
        for i=1,steps do
            local t = tmp[i]
            fractions[i] = t[1]
            color_a  [i] = t[2]
            color_b  [i] = t[3]
        end
        -- So far for a fix.
        for i=1,steps do
            if i < steps then
                bounds[i] = fractions[i] or 1
            end
            encode[2*i-1] = 0
            encode[2*i]   = 1
            list  [i]     = pdfdictionary {
                FunctionType = 2,
                Domain       = domain,
                C0           = pdfarray(color_a[i]),
                C1           = pdfarray(color_b[i]),
                N            = n,
            }
        end
        func = pdfdictionary {
            FunctionType = 3,
            Bounds       = bounds,
            Encode       = encode,
            Functions    = list,
            Domain       = domain,
        }
    else
        func = pdfdictionary {
            FunctionType = 2,
            Domain       = domain,
            C0           = pdfarray(color_a),
            C1           = pdfarray(color_b),
            N            = n,
        }
    end
    separation = separation and registrations.getspotcolorreference(separation)
    local s = pdfdictionary {
        ShadingType = stype,
        ColorSpace  = separation and pdfreference(separation) or pdfconstant(colorspace),
        Domain      = domain,
        Function    = pdfreference(pdfflushobject(func)),
        Coords      = pdfarray(coordinates),
        Extend      = pdfarray { true, true },
        AntiAlias   = pdfboolean(true),
    }
    lpdf.adddocumentshade(name,pdfreference(pdfflushobject(s)))
end

function lpdf.circularshade(name,domain,color_a,color_b,n,colorspace,coordinates,separation,steps,fractions)
    shade(3,name,domain,color_a,color_b,n,colorspace,coordinates,separation,steps,fractions)
end

function lpdf.linearshade(name,domain,color_a,color_b,n,colorspace,coordinates,separation,steps,fractions)
    shade(2,name,domain,color_a,color_b,n,colorspace,coordinates,separation,steps,fractions)
end

-- inline bitmaps but xform'd
--
-- we could derive the colorspace if we strip the data
-- and divide by x*y

-- todo: map onto png


do

    local template = "q BI %s ID %s > EI Q"
    local factor   = 72/300

    local methods = { }

    methods.hex = function(t)
        -- encoding is ascii hex, no checking here
        local xresolution, yresolution = t.xresolution or 0, t.yresolution or 0
        if xresolution == 0 or yresolution == 0 then
            return -- fatal error
        end
        local colorspace = t.colorspace
        if colorspace ~= "rgb" and colorspace ~= "cmyk" and colorspace ~= "gray" then
            -- not that efficient but ok
            local d = gsub(t.data,"[^0-9a-f]","")
            local b = round(#d / (xresolution * yresolution))
            if b == 2 then
                colorspace = "gray"
            elseif b == 6 then
                colorspace = "rgb"
            elseif b == 8 then
                colorspace = "cmyk"
            end
        end
        colorspace = lpdf.colorspaceconstants[colorspace]
        if not colorspace then
            return -- fatal error
        end
        --the original length L is required for pdf 2.0 (4096 max)
        local d = pdfdictionary {
            W   = xresolution,
            H   = yresolution,
            CS  = colorspace,
            BPC = 8,
            F   = pdfconstant("AHx"),
         -- CS  = nil,
         -- BPC = 1,
         -- IM = true,
        }
        -- for some reasons it only works well if we take a 1bp boundingbox
        local urx, ury = 1/basepoints, 1/basepoints
     -- urx = (xresolution/300)/basepoints
     -- ury = (yresolution/300)/basepoints
        local width, height = t.width or 0, t.height or 0
        if width == 0 and height == 0 then
            width  = factor * xresolution / basepoints
            height = factor * yresolution / basepoints
        elseif width == 0 then
            width  = height * xresolution / yresolution
        elseif height == 0 then
            height = width  * yresolution / xresolution
        end
        local a = pdfdictionary {
            BBox = pdfarray { 0, 0, round(urx * basepoints), round(ury * basepoints) }
        }
        local image = createimage {
            stream = formatters[template](d(),t.data),
            width  = width,
            height = height,
            bbox   = { 0, 0, round(urx), round(ury) },
            attr   = a(),
            nobbox = true,
        }
        return wrapimage(image)
    end

 -- local lpegmatch     = lpeg.match
 -- local pattern       = lpeg.Cs((lpeg.patterns.space/"" + lpeg.patterns.hextobyte)^0)

    local zlibcompress    = xzip.compress
    local hextocharacters = string.hextocharacters
    local compresslevel   = 3

    methods.png = function(t)
        -- encoding is ascii hex, no checking here
        local xresolution = t.xresolution or 0
        local yresolution = t.yresolution or 0
        local data        = t.data or ""
        if xresolution == 0 or yresolution == 0 or data == "" then
            return -- fatal error
        end
        data = hextocharacters(data)
        if not data then
            return
        end
        local colorspace = t.colorspace
        local colordepth = 8
        local colors     = 1
--         if colorspace ~= "rgb" and colorspace ~= "gray" then
--             -- not that efficient but ok
--             local d = gsub(t.data,"[^0-9a-f]","")
--             local b = round(#d / (xresolution * yresolution))
--             if b == 2 then
--                 colorspace = "gray"
--                 colors     = 1
--             elseif b == 6 then
--                 colorspace = "rgb"
--                 colors     = 3
--             elseif b == 8 then
--                 return -- for now, todo: convert
--             end
--         end
        if colorspace ~= "rgb" and colorspace ~= "gray" then
            local b = round(#data / (xresolution * yresolution))
            if b == 1 then
                colorspace = "gray"
                colors     = 1
            elseif b == 3 then
                colorspace = "rgb"
                colors     = 3
            elseif b == 4 then
                return -- for now, todo: convert
            end
        end
        colorspace = lpdf.colorspaceconstants[colorspace]
        if not colorspace then
            return -- fatal error
        end
        local width  = t.width
        local height = t.height
        if width == 0 and height == 0 then
            width  = factor * xresolution / basepoints
            height = factor * yresolution / basepoints
        elseif width == 0 then
            width  = height * xresolution / yresolution
        elseif height == 0 then
            height = width  * yresolution / xresolution
        end
     -- data = zlibcompress(lpegmatch(pattern,data),compresslevel)
        data = zlibcompress(data,compresslevel)
        local xobject = pdfdictionary {
            Type             = pdfconstant("XObject"),
            Subtype          = pdfconstant("Image"),
            Width            = xresolution,
            Height           = yresolution,
            BitsPerComponent = 8,
            ColorSpace       = colorspace,
            Length           = #data,
            Filter           = pdfconstant("FlateDecode"),
        }
        local image = createimage {
--             bbox     = { 0, 0, round(width/xresolution), round(height/yresolution) }, -- mandate
            bbox     = { 0, 0, round(width), round(height) }, -- mandate
            width    = round(width),
            height   = round(height),
            nolength = true,
            nobbox   = true,
            notype   = true,
            stream   = data,
            attr     = xobject(),
        }
        return wrapimage(image)
    end

    function nodeinjections.injectbitmap(t)
        if t.colorspace == "cmyk" then
            return methods.hex(t)
        else
            return (methods[t.format or "hex"] or methods.hex)(t)
        end
    end

end

function codeinjections.setfigurealternative(data,figure)
    local request = data.request
    local display = request.display
    if display and display ~= ""  then
        local nested = figures.push {
            name   = display,
            page   = request.page,
            size   = request.size,
            prefix = request.prefix,
            cache  = request.cache,
            width  = request.width,
            height = request.height,
        }
        figures.identify()
        local displayfigure = figures.check()
        if displayfigure then
        --  figure.aform = true
            embedimage(figure)
            local a = pdfarray {
                pdfdictionary {
                    Image              = pdfreference(figure.objnum),
                    DefaultForPrinting = true,
                }
            }
            local d = pdfdictionary {
                Alternates = pdfreference(pdfflushobject(a)),
            }
            displayfigure.attr = d()
            figures.pop()
            return displayfigure, nested
        else
            figures.pop()
        end
    end
end

function codeinjections.getpreviewfigure(request)
    local figure = figures.initialize(request)
    if not figure then
        return
    end
    figure = figures.identify(figure)
    if not (figure and figure.status and figure.status.fullname) then
        return
    end
    figure = figures.check(figure)
    if not (figure and figure.status and figure.status.fullname) then
        return
    end
    local image = figure.status.private
    if image then
        embedimage(image)
    end
    return figure
end

local masks = {
    demomask = {
        {   0,  63,   0 },
        {  64, 127, 127 },
        { 128, 195, 195 },
        { 196, 255, 255 },
    }
}

local ranges = {
--     [".75"] = .75,
--     [".50"] = .50,
--     [".25"] = .25,
}

function codeinjections.registerfiguremask(name,specification)
    masks[name] = specification
end

function codeinjections.registerfigurerange(name,specification)
    ranges[name] = specification
end

function codeinjections.setfiguremask(data,figure) -- mark
    local request = data.request
    local mask    = request.mask
    local range   = request.range
    if mask and mask ~= ""  then
        local m = masks[mask]
        if m then
            if type(m) == "function" then
                m = m()
            end
            figure.newmask = m
        else
            figures.push {
                name   = mask,
                page   = request.page,
                size   = request.size,
                prefix = request.prefix,
                cache  = request.cache,
                width  = request.width,
                height = request.height,
            }
            mask = figures.identify()
            mask = figures.check(mask)
            if mask then
                local image = mask.status.private
                if image then
                    figures.include(mask)
                    embedimage(image)
                    local d = pdfdictionary {
                        Interpolate  = false,
                        SMask        = pdfreference(mask.status.objectnumber),
                    }
                    figure.attr = d()
                end
            end
            figures.pop()
        end
    end
    if range and range ~= "" then
        local r = ranges[range]
        if not r then
            r = tonumber(range)
        end
        if type(r) == "function" then
            r = r()
        end
        figure.newranges = r
    end
end

-- experimental (q Q is not really needed)

local saveboxresource = tex.boxresources.save
local nofpatterns     = 0
local f_pattern       = formatters["q /Pattern cs /%s scn 0 0 %.6N %.6N re f Q"]

function lpdf.registerpattern(specification)
    nofpatterns = nofpatterns + 1
    local d = pdfdictionary {
        Type        = pdfconstant("Pattern"),
        PatternType = 1,
        PaintType   = 1,
        TilingType  = 2,
        XStep       = (specification.width  or 10) * basepoints,
        YStep       = (specification.height or 10) * basepoints,
        Matrix      = {
            1, 0, 0, 1,
            (specification.hoffset or 0) * basepoints,
            (specification.voffset or 0) * basepoints,
        },
    }

 -- local resources  = lpdf.collectedresources{ patterns = false } -- we don't want duplicates, so no serialize here:
    local resources  = lpdf.collectedresources{ patterns = false, serialize = false }
    local attributes = d -- () -- we need to check for patterns
    local onlybounds = 1
    local patternobj = saveboxresource(specification.number,attributes,resources,true,onlybounds)
    lpdf.adddocumentpattern("Pt" .. nofpatterns,lpdf.reference(patternobj ))
    return nofpatterns
end

function lpdf.patternstream(n,width,height)
    return f_pattern("Pt" .. n,width*basepoints,height*basepoints)
end

codeinjections.registerpattern = lpdf.registerpattern