Converting png to pdf with PIL save mode error

Question

Im trying to convert png files into pdf's. PIL seems to be the way to do it but Im getting an error (cannot save mode RGBA) when running it

Code:

import os
import PIL
from PIL import Image

path = 'E:\path_to_file'
filename = '15868799_1.png'
fullpath_filename = os.path.join(path, filename)
im = PIL.Image.open(fullpath_filename)
newfilename = '15868799.pdf'
newfilename_fullpath = os.path.join(path, newfilename)
PIL.Image.Image.save(im, newfilename_fullpath, "PDF", resoultion=100.0)

Error:

 File "C:\Python\lib\site-packages\PIL\PdfImagePlugin.py", line 148, in _save
 raise ValueError("cannot save mode %s" % im.mode)
 ValueError: cannot save mode RGBA

Answer 1

You need to convert your PNG from RGBA to RGB first.

Sample code:

from PIL import Image

PNG_FILE = 'E:\path_to_file\15868799_1.png'
PDF_FILE = 'E:\path_to_file\15868799.pdf'

rgba = Image.open(PNG_FILE)
rgb = Image.new('RGB', rgba.size, (255, 255, 255))  # white background
rgb.paste(rgba, mask=rgba.split()[3])               # paste using alpha channel as mask
rgb.save(PDF_FILE, 'PDF', resoultion=100.0)

Answer 2

To convert multiple RGBA png images, I opted for this code piece,

from PIL import Image

_source = "/mnt/ssd/presentations"

_files = [] # List of image path populated using glob

def conv_rgba_to_rgb(_rgba):
  _rgba = Image.open(_rgba)
  _rgb = Image.new('RGB', _rgba.size, (255, 255, 255))
  _rgb.paste(_rgba, mask=_rgba.split()[3])
  return _rgb

_images = [conv_rgba_to_rgb(_f) for _f in _files]
_pdf_path = f"{_source}/phd-presentation.pdf"
_images[0].save(_pdf_path, "PDF", resolution=72.0, save_all=True, append_images=_images[1:])