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 = table.concat
local round = math.round

local backends, lpdf = backends, lpdf

local nodeinjections = backends.pdf.nodeinjections

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

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

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()
        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

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

function nodeinjections.injectbitmap(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 = math.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
    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, urx * basepoints, ury * basepoints }
    }
    local image = createimage {
        stream = formatters[template](d(),t.data),
        width  = width,
        height = height,
        bbox   = { 0, 0, urx, ury },
        attr   = a(),
        nobbox = true,
    }
    return wrapimage(image)
end

-- general graphic helpers

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

function codeinjections.setfiguremask(data,figure) -- mark
    local request = data.request
    local mask    = request.mask
    if mask and mask ~= ""  then
        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

-- experimental (q Q is not really needed)

local f_pattern = formatters["q /Pattern cs /%s scn 0 0 %.6F %.6F re f Q"]

directives.register("pdf.stripzeros",function()
    f_pattern = formatters["q /Pattern cs /%s scn 0 0 %.6N %.6N re f Q"]
end)

local saveboxresource  = tex.boxresources.save
local nofpatterns      = 0

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 }
    local attributes = d()
    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
