Make PNG library optional.

Refs #338

qrcode/compat/png.py

@@ -0,0 +1,7 @@
+# Try to import png library.
+PngWriter = None
+
+try:
+ from png import Writer as PngWriter # type: ignore # noqa: F401
+except ImportError: # pragma: no cover
+ pass

qrcode/image/pure.py

@@ -1,11 +1,10 @@
 from itertools import chain
 
-import png
+from qrcode.compat.png import PngWriter
+from qrcode.image.base import BaseImage
 
-import qrcode.image.base
 
-
-class PyPNGImage(qrcode.image.base.BaseImage):
+class PyPNGImage(BaseImage):
  """
  pyPNG image builder.
  """
@@ -15,7 +14,7 @@ class PyPNGImage(qrcode.image.base.BaseImage):
  needs_drawrect = False
 
  def new_image(self, **kwargs):
- return png.Writer(self.pixel_size, self.pixel_size, greyscale=True, bitdepth=1)
+ return PngWriter(self.pixel_size, self.pixel_size, greyscale=True, bitdepth=1)
 
  def drawrect(self, row, col):
  """

qrcode/tests/test_qrcode.py

@@ -4,11 +4,11 @@
 from tempfile import mkdtemp
 from unittest import mock
 
-import png
 
 import qrcode
 import qrcode.util
 from qrcode.compat.pil import Image as pil_Image
+from qrcode.compat.png import PngWriter
 from qrcode.exceptions import DataOverflowError
 from qrcode.image.base import BaseImage
 from qrcode.image.pure import PyPNGImage
@@ -174,20 +174,22 @@ class MockFactory(BaseImage):
  self.assertTrue(MockFactory.new_image.called)
  self.assertTrue(MockFactory.drawrect.called)
 
+ @unittest.skipIf(not PngWriter, "Requires PNG")
  def test_render_pypng(self):
  qr = qrcode.QRCode()
  qr.add_data(UNICODE_TEXT)
  img = qr.make_image(image_factory=PyPNGImage)
- self.assertIsInstance(img.get_image(), png.Writer)
+ self.assertIsInstance(img.get_image(), PngWriter)
 
  print(img.width, img.box_size, img.border)
  img.save(io.BytesIO())
 
+ @unittest.skipIf(not PngWriter, "Requires PNG")
  def test_render_pypng_to_str(self):
  qr = qrcode.QRCode()
  qr.add_data(UNICODE_TEXT)
  img = qr.make_image(image_factory=PyPNGImage)
- self.assertIsInstance(img.get_image(), png.Writer)
+ self.assertIsInstance(img.get_image(), PngWriter)
 
  mock_open = mock.mock_open()
  with mock.patch("qrcode.image.pure.open", mock_open, create=True):

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 distribute = False
-envlist = py{39,310,311,312}-{pil,nopil}
+envlist = py{39,310,311,312}-{pil,png,none}
 skip_missing_interpreters = True
 
 [gh-actions]
@@ -15,5 +15,6 @@ commands =
  pytest {envsitepackagesdir}/qrcode
 deps =
  pil: pillow>=9.1.0
+ png: pypng
  pytest
  pytest-cov