PDF export has inaccurate dimensions

Question

Bug introduced in 11.2 or earlier and persisting through 13.0.0 [CASE:4895073]

---

The following code produces a 10x10 grid of numbers, each in a 20x6 mm cell.

mm = 72/25.4;
{bx, by} = {20 mm, 6 mm};
label[num_] := Graphics[
  Text[IntegerString[num, 10, 5], {10 mm, 3 mm}],
  ImageSize -> {bx, by}, PlotRange -> {{0, bx}, {0, by}}, 
  PlotRangePadding -> None]
labels = label /@ Range[100];
GraphicsGrid[Partition[labels, 10], Spacings -> 0]
Export["number.pdf", %]

When exporting to PDF, irrespective of the number of cells (even for a single cell without GraphicsGrid), the PDF dimensions are not exact.

The exact dimensions should be 10x20 mm wide and 10x6 mm long, i.e. 200 x 60 mm.

However, the actual output has dimensions of 204.3 x 64.6 mm.

How to resolve this ? Mathematica version is 11.2 running on Win 10 x64.

Of course, I could just add an approximate factor of ~0.979 in the mm definition, but that way it won't be really exact and will look ugly when merged with other graphics (in another program).

Answer 1

First of all, as chuy correctly points out in the comments, you should set PrintingStyleEnvironment to "Working" in order to avoid magnification problems discussed here:

SetOptions[$FrontEndSession, PrintingStyleEnvironment -> "Working"]

Then, I suggest to use Grid instead of GraphicsGrid (the value -.11 is found by trial and error):

Grid[Partition[labels, 10], Spacings -> {0, -.11}]
Export["number.pdf", %] // SystemOpen

The above screenshot is of the PDF file exported with Mathematica 13.0.0 on Windows 10 x64.

But with Mathematica 12.3.1 and 8.0.4 I get a PDF image of size 201 x 60 mm. This is version-dependent since even the actual meaning of ImageSize changed significantly in the latest versions, apart from updated PDF exporter.

If you need exact control over the size of the final image, the best what you can do is to make a Graphics object with your contents by using low-level functions like Inset and Text, and not relying on any high-level functionality.

An example:

mm = 72/25.4;
coords = Flatten[Table[{x, y}, {y, 1, 10}, {x, 1, 10}], 1];
labels = IntegerString[Range[100], 10, 5];
imageSize = {200 mm, 60 mm};
gr = Graphics[MapThread[Text, {labels, coords}], 
   PlotRange -> {{.5, 10.5}, {.5, 10.5}}, PlotRangePadding -> 0, 
   ImageSize -> imageSize, AspectRatio -> 1/Divide @@ imageSize];
Export["number.pdf", gr] // SystemOpen

This should give the exact size of the exported PDF, but even with version 13.0.0 it does not:

... but version 8.0.4 exports a PDF with exact image size:

Hence we have a regression in the PDF exporter in the latest Mathematica versions. Reported to the support as [CASE:4895073].

Update. I just received a response from the support. Here is an excerpt:

Thank you for taking the time to send your report.

It does appear that Export[] is not preserving the specified image size with the PDF files it generates. <...>

This issue appears to have started in Mathematica 12.1, so any earlier versions should not exhibit this behavior.

Answer 2

For those interested, here is a workaround using matplotlib of Python.

import numpy as np
import matplotlib.pyplot as plt
mm = 1 / 25.4
#Array size
nx = 10
ny = 40
#Cell size
cx = 20mm
cy = 6mm
#relative position (left-center justified) of text in cell
npx = 0.25
npy = 0.7
plt.figure(figsize=(cxnx, cyny))
for x in (np.arange(nx)+1):
    for y in (np.arange(ny)+1):
        plt.figtext( (npx+x-1)/nx, (npy+y-1)/ny, f'{x+nx(y-1):06.0f}', horizontalalignment='left', verticalalignment='center', size=723*mm, fontfamily='consolas', weight='bold')
plt.savefig("numbers-py.pdf")