params =
    "graphics": "<h1>test</h1>"

d3.xhr(pdf_url.toString())
    .header("X-CSRFToken", document.csrf_cookie)
    .header("Content-Type", "application/json")
    .header("Accept", "application/pdf")
    .post JSON.stringify(params), (error, pdf_data) ->
        if error
            console.log(error)
        else
            a = document.createElement("a")
            file = new Blob [pdf_data.response], "type": "application/pdf"
            url = URL.createObjectURL(file)
            a.href = url
            a.download = "#{params['title']} #{params['filter']}.pdf"
            document.body.appendChild(a)
            a.click()
            setTimeout ->
                document.body.removeChild(a)
                window.URL.revokeObjectURL(url)
            , 0