Why in this PDF file generated in this example my watermark is not displayed?

问题

Why in this PDF file generated in this example my watermark is not displayed? How can I fix it? (There is no error, just does not display "WATERMARK".)

https://docs.djangoproject.com/en/dev/howto/outputting-pdf/#outputting-pdfs-with-django

import xhtml2pdf
from xhtml2pdf import pisa
import reportlab
from reportlab.pdfgen import canvas

def delivery_cancel(request, did):
    d_instance = get_object_or_404(Delivery, pk=did, user=request.user)
    users = request.user.get_profile()
    user = request.user
    contents = render_to_string('delivery_cancel.html', {'delivery':d_instance,'users':users,'user':user})
    response = HttpResponse(mimetype='application/pdf')
    response['Content-Disposition'] = 'inline; filename=mypdf.pdf'
    result = StringIO.StringIO()
    pdf = pisa.pisaDocument(StringIO.StringIO(contents.encode('utf-8')), result, show_error_as_pdf=True, encoding='UTF-8')
    x = canvas.Canvas(pdf)
    x.drawString(100, 100, 'WATERMARK')
    x.save()
    response.write(result.getvalue())
    result.close()
    return response

EDIT:

def delivery_cancel(request, did):
    d_instance = get_object_or_404(Delivery, pk=did, user=request.user)
    users = request.user.get_profile()
    user = request.user
    contents = render_to_string('delivery_cancel.html', {'delivery':d_instance,'users':users,'user':user})
    response = HttpResponse(mimetype='application/pdf')
    response['Content-Disposition'] = 'inline; filename=mypdf.pdf'
    content_stream = StringIO.StringIO(contents.encode('utf-8'))
    x = canvas.Canvas(content_stream)
    x.drawString(100, 100, 'WATERMARK')
    x.showPage()
    x.save()
    result = StringIO.StringIO()
    pdf = pisa.pisaDocument(content_stream, result, show_error_as_pdf=True, encoding='UTF-8')
    response.write(result.getvalue())
    result.close()
    return response

Now watermark is missing and looks like that pisaDocument not working because PDF format looks different. (or I did something wrong again)

来源：https://stackoverflow.com/questions/20838212/why-in-this-pdf-file-generated-in-this-example-my-watermark-is-not-displayed

标签

python

django

reportlab