Python reportlab put an image in a canvasmaker

Question

I'd like to put an image (a barcode more precisely) in a pdf doc generated by reportlab. I can put it in a table. That works perfectly with createBarcodeDrawing().

The point is that I'd like the barcode to change on each page. Thus, I want to put it in a canvasmaker.

Whatever method I use (drawImage(), drawInLineImage(),...), I always have an error. I even tried to use CustomImage from Reportlab [ Platypus ] - Image does not render without any success. Consequently, my question is how can I draw an image in a canvas.Canvas ?

Can anybody help ? Thank you in advance Dom (I am not a professional)

Following a remark I read on http://www.tylerlesmann.com/2009/jan/28/writing-pdfs-python-adding-images/, I tried:

img = 'apple-logo.jpg'
self.drawInlineImage('C:\\'+img,20,20)

This works, while 'C:\apple-logo.jpg' doesn't !! Nevertheless, I still don't know how to draw my barcode without writing it to a file before! If someone manages to do it, I would really appreciate. Bye

from reportlab.pdfgen import canvas
from reportlab.lib.units import mm


class NumberedCanvas(canvas.Canvas):
def __init__(self, *args, **kwargs):
    canvas.Canvas.__init__(self, *args, **kwargs)
    self._saved_page_states = []

def showPage(self):
    self._saved_page_states.append(dict(self.__dict__))
    self._startPage()

def save(self):
    """add page info to each page (page x of y)"""
    num_pages = len(self._saved_page_states)
    for state in self._saved_page_states:
        self.__dict__.update(state)
        page_num = self._pageNumber
        mybarcode = createBarcodeDrawing('QR', value= 'www.mousevspython.com - Page %s'%page_num)
        self.drawInlineImage(mybarcode,20,20)
        canvas.Canvas.showPage(self)
    canvas.Canvas.save(self)

def main():
import sys
import urllib2
from cStringIO import StringIO
from reportlab.platypus import SimpleDocTemplate, Image, Paragraph, PageBreak
from reportlab.lib.styles import ParagraphStyle, getSampleStyleSheet

#This is needed because ReportLab accepts the StringIO as a file-like object,
#but doesn't accept urllib2.urlopen's return value
def get_image(url):
    u = urllib2.urlopen(url)
    return StringIO(u.read())

styles = getSampleStyleSheet()
styleN = ParagraphStyle(styles['Normal'])

# build doc

if len(sys.argv) > 1:
    fn = sys.argv[1]
else:
    fn = "filename.pdf"
doc = SimpleDocTemplate(open(fn, "wb"))
elements = [
    Paragraph("Hello,", styleN),
    Image(get_image("http://www.red-dove.com/images/rdclogo.gif")),
    PageBreak(),
    Paragraph("world!", styleN),
    Image(get_image("http://www.python.org/images/python-logo.gif")),
]
doc.build(elements, canvasmaker=NumberedCanvas)

if __name__ == "__main__":
main()

Answer 1

You were nearly there. Just replace self.drawImage(mybarcode,20,20) with mybarcode.drawOn(self, 20, 20). The barcode is not really an image, more an barcode object which you can export to an image. As a side note: You are using the NumberedCanvas which is kind of a hack to get the total page count. As i see it you don't really need it, as you are just using the current page number. If you don't need the total page count, you can just define a canvas drawing function which draws the barcode on each page. For this you would do something like this:

def draw_barcode(canvas, doc):
    canvas.saveState()
    page_num = canvas._pageNumber
    mybarcode = createBarcodeDrawing('QR', value= 'www.mousevspython.com - Page %s'%page_num)
    mybarcode.drawOn(canvas, 20, 20)
    canvas.restoreState()

[...]

# doc.build(elements, canvasmaker=NumberedCanvas)
doc.build(elements, onFirstPage=draw_barcode, onLaterPages=draw_barcode)