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Correct paper sizes #22544

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Merged
merged 1 commit into from
Mar 3, 2022
Merged

Correct paper sizes #22544

merged 1 commit into from
Mar 3, 2022

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oscargus
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PR Summary

Stumbled upon this code which doesn't seem correct (height of A8 should be same as width of A9).

matplotlib/lib/matplotlib/backends/backend_ps.py

Lines 63 to 65 in 581bf5d

'a8': (2.07, 2.91),
'a9': (1.457, 2.05),
'a10': (1.02, 1.457),

Spent some time reading up on paper sizes and cannot really say that I know what the correct answer is, but this is what I learnt:

  • The ratio between height and width is sqrt(2)
  • A0 is 1 square meter
  • Width => height for next smaller size

This gives, in mm

a0 : (840.896415253715, 1189.20711500272)
a1 : (594.603557501361, 840.896415253715)
a2 : (420.448207626857, 594.603557501361)
a3 : (297.301778750680, 420.448207626857)
a4 : (210.224103813429, 297.301778750680)
a5 : (148.650889375340, 210.224103813429)
a6 : (105.112051906714, 148.650889375340)
a7 : (74.3254446876701, 105.112051906714)
a8 : (52.5560259533572, 74.3254446876701)
a9 : (37.1627223438350, 52.5560259533572)
a10 : (26.2780129766786, 37.1627223438350)

Now, all these are rounded down, except for a0 width/a1 height, based on the tables available.

Converting to inches there are two approaches: converting the exact expression or using the expression in integer mm.

For the first, the sizes are:

a0 : (33.1061580808549, 46.8191777560126)
a1 : (23.4095888780063, 33.1061580808549)
a2 : (16.5530790404275, 23.4095888780063)
a3 : (11.7047944390032, 16.5530790404275)
a4 : (8.27653952021373, 11.7047944390032)
a5 : (5.85239721950158, 8.27653952021373)
a6 : (4.13826976010686, 5.85239721950158)
a7 : (2.92619860975079, 4.13826976010686)
a8 : (2.06913488005343, 2.92619860975079)
a9 : (1.46309930487540, 2.06913488005343)
a10 : (1.03456744002672, 1.46309930487540)

For integer mm:

a0 : (33.1102362204724, 46.8110236220472)
a1 : (23.3858267716535, 33.1102362204724)
a2 : (16.5354330708661, 23.3858267716535)
a3 : (11.6929133858268, 16.5354330708661)
a4 : (8.26771653543307, 11.6929133858268)
a5 : (5.82677165354331, 8.26771653543307)
a6 : (4.13385826771654, 5.82677165354331)
a7 : (2.91338582677165, 4.13385826771654)
a8 : (2.04724409448819, 2.91338582677165)
a9 : (1.45669291338583, 2.04724409448819)
a10 : (1.02362204724409, 1.45669291338583)

Checking all the other numbers, it seems like using the last table gives the smallest changes.

One can of course use 1.457 for a9/a10, but then one should probably use 1.024 for a10.

PR Checklist

Tests and Styling

  • Has pytest style unit tests (and pytest passes).
  • Is Flake 8 compliant (install flake8-docstrings and run flake8 --docstring-convention=all).

Documentation

  • New features are documented, with examples if plot related.
  • New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
  • API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).
  • Documentation is sphinx and numpydoc compliant (the docs should build without error).

@oscargus oscargus changed the title Correct papersizes Correct paper sizes Feb 23, 2022
@QuLogic
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QuLogic commented Feb 24, 2022

Width => height for next smaller size

And, due to the ratio, the width of the smaller size is half the height of larger.

The smallest tolerance is 0.06 in, so I think rounding to 2 decimal places might be okay, though of course on a computer things can be much more precise than physical paper.

@tacaswell tacaswell added this to the v3.6.0 milestone Mar 3, 2022
@QuLogic QuLogic merged commit f33f5ab into matplotlib:main Mar 3, 2022
@oscargus oscargus deleted the papersizes branch March 3, 2022 08:33
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@tacaswell tacaswell tacaswell approved these changes

@QuLogic QuLogic QuLogic approved these changes

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