From 732a70764d712ae783dbb455933411196061002d Mon Sep 17 00:00:00 2001
From: Martin Thoma <info@martin-thoma.de>
Date: Sat, 23 Apr 2022 09:19:41 +0200
Subject: [PATCH 1/2] ENH: Add papersizes

---
 PyPDF2/__init__.py       | 11 +++++----
 PyPDF2/papersizes.py     | 48 ++++++++++++++++++++++++++++++++++++++++
 Tests/test_papersizes.py | 30 +++++++++++++++++++++++++
 3 files changed, 85 insertions(+), 4 deletions(-)
 create mode 100644 PyPDF2/papersizes.py
 create mode 100644 Tests/test_papersizes.py

diff --git a/PyPDF2/__init__.py b/PyPDF2/__init__.py
index 07f211c2b..0d21401ff 100644
--- a/PyPDF2/__init__.py
+++ b/PyPDF2/__init__.py
@@ -1,11 +1,14 @@
-from ._version import __version__
-from .merger import PdfFileMerger
-from .pagerange import PageRange, parse_filename_page_ranges
-from .pdf import PdfFileReader, PdfFileWriter
+from PyPDF2._version import __version__
+from PyPDF2.merger import PdfFileMerger
+from PyPDF2.pagerange import PageRange, parse_filename_page_ranges
+from PyPDF2.papersizes import PaperSize
+from PyPDF2.pdf import PdfFileReader, PdfFileWriter
+from PyPDF2 import pdf
 
 __all__ = [
     "__version__",
     "PageRange",
+    "PaperSize",
     "parse_filename_page_ranges",
     "pdf",
     "PdfFileMerger",
diff --git a/PyPDF2/papersizes.py b/PyPDF2/papersizes.py
new file mode 100644
index 000000000..c3c0819ab
--- /dev/null
+++ b/PyPDF2/papersizes.py
@@ -0,0 +1,48 @@
+"""Helper to get paper sizes."""
+
+from collections import namedtuple
+
+Dimensions = namedtuple("Dimensions", ["width", "height"])
+
+
+class PaperSize(object):
+    """(width, height) of the paper in portrait mode in pixels at 72 ppi."""
+
+    # Notes how to calculate it:
+    # 1. Get the size of the paper in mm
+    # 2. Convert it to inches (25.4 millimeters are equal to 1 inches)
+    # 3. Convert it to pixels ad 72dpi (1 inch is equal to 72 pixels)
+
+    # All Din-A paper sizes follow this pattern:
+    # 2xA(n-1) = A(n)
+    # So the height of the next bigger one is the width of the smaller one
+    # The ratio is always approximately the ratio 1:2**0.5
+    # Additionally, A0 is defined to have an area of 1 m**2
+    # Be aware of rounding issues!
+    A0 = Dimensions(2384, 3370)  # 841mm x 1189mm
+    A1 = Dimensions(1684, 2384)
+    A2 = Dimensions(1191, 1684)
+    A3 = Dimensions(842, 1191)
+    A4 = Dimensions(
+        595, 842
+    )  # Printer paper, documents - this is by far the most common
+    A5 = Dimensions(420, 595)  # Paperback books
+    A6 = Dimensions(298, 420)  # Post cards
+    A7 = Dimensions(210, 298)
+    A8 = Dimensions(147, 210)
+
+    # Envelopes
+    C4 = Dimensions(649, 918)
+
+
+_din_a = [
+    PaperSize.A0,
+    PaperSize.A1,
+    PaperSize.A2,
+    PaperSize.A3,
+    PaperSize.A4,
+    PaperSize.A5,
+    PaperSize.A6,
+    PaperSize.A7,
+    PaperSize.A8,
+]
diff --git a/Tests/test_papersizes.py b/Tests/test_papersizes.py
new file mode 100644
index 000000000..73aad23cd
--- /dev/null
+++ b/Tests/test_papersizes.py
@@ -0,0 +1,30 @@
+from PyPDF2 import papersizes
+import pytest
+
+
+def test_din_a0():
+    dim = papersizes.PaperSize.A0
+    area_square_pixels = dim.width * dim.height
+
+    # 72 pixels is 1 inch
+    area_square_inch = area_square_pixels / 72**2
+
+    # 25.4 millimeter is equal to 1 inches
+    area_square_mm = area_square_inch * (25.4)**2
+    assert abs(area_square_mm - 999949) < 100
+    conversion_factor = 72 / 25.4
+    assert (dim.width - 841 * conversion_factor) < 1
+    assert (dim.width - 1189 * conversion_factor) < 1
+
+
+
+@pytest.mark.parametrize("dimensions", papersizes._din_a)
+def test_din_a_ratio(dimensions):
+    assert abs(dimensions.height - dimensions.width * 2**0.5) <= 2.5
+
+
+@pytest.mark.parametrize(
+    "dimensions_a, dimensions_b", list(zip(papersizes._din_a, papersizes._din_a[1:]))
+)
+def test_din_a_doubling(dimensions_a, dimensions_b):
+    assert abs(dimensions_a.height - 2 * dimensions_b.width) <= 4

From f46ef7454494cdf604562224a52d286e7fc1040a Mon Sep 17 00:00:00 2001
From: Martin Thoma <info@martin-thoma.de>
Date: Sat, 23 Apr 2022 09:32:31 +0200
Subject: [PATCH 2/2] float for Python 2.7

---
 Tests/test_papersizes.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Tests/test_papersizes.py b/Tests/test_papersizes.py
index 73aad23cd..b198fbe49 100644
--- a/Tests/test_papersizes.py
+++ b/Tests/test_papersizes.py
@@ -4,7 +4,7 @@
 
 def test_din_a0():
     dim = papersizes.PaperSize.A0
-    area_square_pixels = dim.width * dim.height
+    area_square_pixels = float(dim.width) * dim.height
 
     # 72 pixels is 1 inch
     area_square_inch = area_square_pixels / 72**2