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global pdfscanner

The pdfscanner library allows interpretation of PDF content streams and /ToUnicode (cmap) streams. You can get those streams from the pdfe library.

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methods

pdfscanner.scan

function pdfscanner.scan(
  pdf: (string|PdfeStream|PdfeArray),
  operatortable: Operatorable,
  info: table
)

The first argument should be a Lua string or a stream or array object coming from the pdfe library. The second argument, operatortable, should be a Lua table where the keys are PDF operator name strings and the values are Lua functions (defined by you) that are used to process those operators. The functions are called whenever the scanner finds one of these PDF operators in the content stream(s). The functions are called with two arguments: the scanner object itself, and the info table that was passed are the third argument to pdfscanner.scan.

Internally, pdfscanner.scan loops over the PDF operators in the stream(s), collecting operands on an internal stack until it finds a PDF operator. If that PDF operator's name exists in operatortable, then the associated function is executed. After the function has run (or when there is no function to execute) the internal operand stack is cleared in preparation for the next operator, and processing continues.

The scanner argument to the processing functions is needed because it offers various methods to get the actual operands from the internal operand stack.

local operatortable = { }

operatortable.Do = function(scanner,info)
    local resources = info.resources
    if resources then
        local val     = scanner:pop()
        local name    = val[2]
        local xobject = resources.XObject
        print(info.space .. "Uses XObject " .. name)
        local resources = xobject.Resources
        if resources then local newinfo =  { space     = info.space .. "  ", resources = resources, } pdfscanner.scan(entry, operatortable, newinfo)
        end
    end
end

local function Analyze(filename)
    local doc = pdfe.open(filename)
    if doc then
        local pages = doc.Pages
        for i=1,#pages do local page = pages[i] local info = { space     = "  " , resources = page.Resources, } print("Page " .. i)
         -- pdfscanner.scan(page.Contents,operatortable,info) pdfscanner.scan(page.Contents(),operatortable,info)
        end
    end
end

Analyze("foo.pdf")

Reference: